GASIFICATION-BASED BIOREFINING AT KRAFT PULP AND PAPER MILLS IN THE UNITED STATES

Commercialization of black liquor and biomass gasification technologies is anticipated in the 2010-2015 timeframe, and synthesis gas from gasifiers can be converted into liquid fuels using catalytic synthesis technologies that are already commercially established today in the gas-to-liquids or coal-to-liquids industries. This paper describes key results from a major assessment of the prospective energy, environmental, and financial performance of commercial gasification-based biorefineries integrated with kraft pulp and paper mills. Seven detailed biorefinery designs were developed for a reference mill in the Southeastern U.S., together with the associated mass/energy balances, air emissions estimates, and capital investment requirements. The biorefineries provide chemical recovery services and coproduce process steam for the mill, some electricity, and one of three liquid fuels: a Fischer-Tropsch synthetic crude oil (which would be refined to vehicle fuels at existing petroleum refineries), dimethyl ether (a diesel engine fuel or propane substitute), or an ethanol-rich mixed-alcohol product. Compared to installing new Tomlinson power/recovery systems, biorefineries would require more capital investment and greater purchases of woody residues for energy use. However, because biorefineries would be more efficient, have lower air emissions, and produce a more diverse product slate, for nearly all cases examined, the internal rate of return (IRR) on the incremental capital investment lies between 14% and 18%, assuming a $50/bbl world oil price. The IRRs would more than double if plausible federal and state financial incentives are captured. Industry-wide adoption of such biorefining in the United States would provide significant energy and environmental benefits to the country. 1 “Navigant” is a service mark of Navigant International, Inc. Navigant Consulting, Inc. (NCI) is not affiliated, associated, or in any way connected with Navigant International, Inc. NCI’s use of “Navigant” is made under license from Navigant International, Inc. INTRODUCTION This paper summarizes results from a recently-completed two-year effort to assess prospective technical viability, commercial viability, and environmental and energy impacts locally and nationally of gasification-based biorefineries making liquid fuels from black liquor and woody biomass residues at kraft pulp and paper mills [1]. The study builds on an earlier study examining the potential for black liquor gasification combined cycle (BLGCC) electricity generation at kraft pulp and paper mills in the United States [2]. The same reference mill – an integrated pulp and paper mill in the Southeast – was used as the basis for analysis in both studies. The biorefinery analysis assumed that gasification technologies will reach commercial readiness in the 2010 to 2015 timeframe and that the risks involved with installing such gasification systems in the post-2010 time frame will be comparable to those of installing a new Tomlinson-based power/recovery system. The implicit assumption is that in the years between the present and the post-2010 time period, research, development, and demonstration will bring gasification technologies to the point where their commercial reliability approaches that of Tomlinson technology. The equipment for downstream processing of the synthesis gas (syngas) from the gasifiers, including for sulfur capture and for catalytic synthesis of liquids, is already commercial in all but one of the process designs examined in this study. Using potential domestic market size and potential for enhancing domestic energy security as screening criteria, our biorefinery analysis identified three liquid products for detailed analysis: Fischer-Tropsch liquids (FTL, a mixture of primarily straight-chain hydrocarbons – olefins and paraffins – that resembles a semi-refined crude oil), dimethyl ether (DME, a propane substitute or diesel-engine fuel), and mixedalcohols (MA, a mixture of ethanol and higher alcohols that is a potential gasoline substitute). Detailed process designs and simulations were pursued for alternative configurations for the manufacture of these products assuming projected commercial (N plant) performance. Environmental impacts were estimated by quantifying emissions of carbon dioxide, sulfur dioxide, nitrogen oxides, carbon monoxide, volatile organic compounds, particulate matter, and total reduced sulfur. A detailed internal rate of return analysis was carried out for each process design. The mill-level energy and environmental performance results were used as a basis for estimating potential national energy/environment impacts under alternative assumptions about the rate at which existing Tomlinson systems would be retired and replaced with biorefineries. Not all results from the study are presented here. For full results, see [1].