Gasoline from Wood Via Integrated Gasification, Synthesis, and Methanol-To- Gasoline Technologies Steven D
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Gasoline from Wood via Integrated Gasification, Synthesis, and Methanol-to- Gasoline Technologies Steven D. Phillips, Joan K. Tarud, Mary J. Biddy, and Abhijit Dutta NREL is a national laboratory of the U.S. Department of Energy, Office of Energy Efficiency & Renewable Energy, operated by the Alliance for Sustainable Energy, LLC. Technical Report NREL/TP-5100-47594 January 2011 Contract No. DE-AC36-08GO28308 Gasoline from Wood via Integrated Gasification, Synthesis, and Methanol-to- Gasoline Technologies Steven D. Phillips, Joan K. Tarud, Mary J. Biddy, and Abhijit Dutta Prepared under Task No. BB07.3710 NREL is a national laboratory of the U.S. Department of Energy, Office of Energy Efficiency & Renewable Energy, operated by the Alliance for Sustainable Energy, LLC. National Renewable Energy Laboratory Technical Report 1617 Cole Boulevard NREL/TP-5100-47594 Golden, Colorado 80401 January 2011 303-275-3000 • www.nrel.gov Contract No. DE-AC36-08GO28308 NOTICE This report was prepared as an account of work sponsored by an agency of the United States government. Neither the United States government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States government or any agency thereof. 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Executive Summary This report documents the National Renewable Energy Laboratory’s (NREL’s) assessment of the feasibility of making gasoline via the methanol-to-gasoline (MTG) route using syngas from a 2,000 dry metric tonne/day (2,205 U.S. ton/day) biomass-fed facility. The thermochemical route of biomass gasification produces a syngas rich in hydrogen and carbon monoxide. The syngas is then converted into methanol, and the methanol is converted to gasoline using the methanol-to-gasoline (MTG) process first developed by Exxon Mobil. Using a methodology similar to that used in previous NREL design reports and a feedstock cost of $50.70/dry U.S. ton ($55.89/dry metric tonne), a plant gate price (PGP) was estimated. For the base case the PGP is predicted to be $16.60/MMBtu ($15.73/GJ) (U.S. $2007) for gasoline and liquefied petroleum gas (LPG) produced from biomass via gasification of wood, methanol synthesis, and the methanol-to-gasoline process (MTG). The corresponding unit prices for gasoline and LPG are $1.95/gallon ($0.52/liter) and $1.53/gallon ($0.40/liter) with yields of 55.1 and 9.3 gallons per U.S. ton of dry biomass (229.9 and 38.8 liters per metric tonne of dry biomass), respectively. For comparison to ethanol, this is $1.39 per gallon ($0.37/liter) ethanol on an energy equivalent basis. In comparison, based on analysis work completed at NREL, the predicted plant gate prices for ethanol produced via the thermochemical and biochemical pathways are $1.57 per gallon ($0.41 per liter) and $1.49 per gallon ($0.39 per liter), respectively (OBP 2009). Note that the PGP is for the base case. A sensitivity analysis is included in the report to demonstrate the impact that modifications in the design and costing assumptions have on the PGP. A range of PGP values is to be expected due to uncertainties in capital costs, yields, and technoeconomic factors. This report is a future look at the potential of the described biomass-to-gasoline process, based on calculations for a mature plant (also called the nth plant) and 2012 technology targets as established in the Multi-Year Technical Plan of the U.S. Department of Energy (DOE) Office of the Biomass Program. In order to achieve the $1.95/gallon ($0.52/liter) PGP, there are critical research milestones that must be achieved. First, the 2012 tar reforming targets of 99.9% tar and 80% methane conversion (among others) are essential. Also, utilization of a fluidized bed MTG reactor, instead of the commercially proven fixed bed, is pertinent in keeping capital costs down. Thus, further research on this type of reactor is needed 1) to verify that at the conditions specified the products generated match the model assumptions and 2) to analyze effects of scale- up on product distribution. It should be emphasized that the PGP for a first-of-a-kind plant will be significantly higher than the PGP for an nth plant. To predict the PGP for this study, a new technoeconomic model was developed in Aspen Plus, based on the model developed for NREL’s thermochemical ethanol design report (Phillips et al. 2007). The necessary process changes were incorporated into a biomass-to-gasoline model using a methanol synthesis operation followed by conversion, upgrading, and finishing to gasoline. Results of the simulation were used to obtain mass and energy flows, which were then used to size and estimate the cost of process equipment in an Excel spreadsheet-based economic model. This report follows the approach taken in the thermochemical ethanol design case: the DOE Office of the Biomass Program’s 2012 research targets were used for the gasifier and tar reformer operation (Phillips et al. 2007). The methanol and MTG processes were modeled using published results. iii A discounted cash flow rate of return (DCFROR) calculation was performed to determine the PGP required to meet a 10% internal rate of return (IRR). A thermal basis approach was used to account for co-products (LPG and electricity). Instead of assigning a market value to co-products and then using income from the sale of those products to offset operating costs, we used total energy production to determine the PGP on a cost per energy basis (e.g., $/MMBtu or $/GJ) using all products in the calculation. The higher heating value of the individual products was then used to calculate the volumetric cost of the fuels and the per-kilowatt-hour cost of electricity. This approach allocates a proportional fraction of the capital and operating costs for the plant to each of the main products. The overall plant efficiency was 42.6% (lower heating value [LHV] basis) and the carbon efficiency to LPG and gasoline was 31%. The efficiency to the desired gasoline product was 37.7% LHV and 28% carbon efficiency. The gasifier efficiency was 74.9%. Potential process improvements include utilizing more of the tail gases to make products other than heat and electricity. Because all of the power for the plant ultimately comes from the biomass fed to the plant, any energy efficiency improvements to the plant should improve product yields. iv Table of Contents Executive Summary ................................................................................................................................... iii Table of Contents ........................................................................................................................................ v List of Figures ............................................................................................................................................ vi List of Tables .............................................................................................................................................. vi 1 Introduction ........................................................................................................................................... 1 1.1 Background ..........................................................................................................................2 1.2 Methanol and Methanol-to-Gasoline (MTG) Technology Discussion ................................4 1.3 Gasoline Discussion .............................................................................................................9 1.4 Analysis Approach .............................................................................................................10 1.5 Process Design Overview ..................................................................................................13 1.6 Feedstock and Plant Size ...................................................................................................15 2 Process Description ........................................................................................................................... 16 2.1 Feed Handling & Preparation – Area 100 ..........................................................................17 2.2