Primus Green Energy to support gas-to-liquids research at Princeton University; comparing STG+ to other GTL platforms
28 March 2013
|Schematic diagram of the Primus STG+ process. Click to enlarge.|
Primus Green Energy Inc., developer of a proprietary process to produce gasoline and other fuels from biomass and/or natural gas (earlier post), will provide financial support to engineers at Princeton University for general research on synthetic fuels, which will include assessments of various gas-to-liquids (GTL) technologies—including Primus’ own STG+—for sustainability and economic viability.
STG+ technology converts syngas into drop-in high-octane gasoline and jet fuel with a conversion efficiency of ~35% by mass of syngas into liquid transportation fuels (the highest documented conversion efficiency in the industry) or greater than 70% by mass of natural gas. The fuels produced from the Primus STG+ technology are very low in sulfur and benzene compared to fuels produced from petroleum, and they can be used directly in vehicle engines as a component of standard fuel formulas and transported via the existing fuel delivery infrastructure.
The work at Princeton University will be conducted in the laboratories of Professor Christodoulos Floudas, Ph.D. Floudas is an expert in chemical process systems engineering, with a specific emphasis on process synthesis and design, interaction of process design and control and process operations. His research has garnered him academic and industry-wide recognition, including the 2001 Professional Progress Award from the American Institute of Chemical Engineers (AIChE), the 2006 Computing in Chemical Engineering Award from the CAST Division of AIChE, and the Presidential Young Investigator award from the National Science Foundation. He was elected in 2011 to the National Academy of Engineering.
Primus’ STG+ platform is a next-generation gas-to-liquids technology that has the potential to have a significant impact on process efficiency standards and economic viability in the alternative fuels industry. As part of my research, I will be comparing STG+ to other leading GTL platforms against a variety of metrics, including financial, technical and sustainability.—Prof. Floudas
Primus Green Energy estimates that the cost of production for its fuels will be competitive with petroleum-based fuels when crude oil is trading at $65 per barrel (oil is currently trading at approximately $95 per barrel). Primus is nearing completion of its demonstration plant, which is expected to reach mechanical completion in Q2 2013, and expects to break ground on its first commercial plant in the first half of 2014.
Primus is also an adviser to the Northeast Woody/Warm-season Biomass Consortium (NEWBio), a group led by Pennsylvania State University that is tasked with developing perennial feedstock production systems and supply chains for biomass feedstocks. NEWBio is supported by a nearly $10 million grant from the U.S. Department of Agriculture.
STG+. STG+ (Syngas To Gasoline +, the plus standing for the multiple end products yielded by the process) essentially improves upon commercial methanol synthesis processes and ExxonMobil’s methanol to gasoline (MTG) process, combining them into a single-loop process that converts syngas directly to gasoline. In addition to the gasoline product, the STG+ process can also produce jet fuel, diesel and high-value chemicals by changing the catalysts and operating conditions.
The Primus STG+ process follows four principal steps in one continuous process loop using four fixed bed reactors in series.
Reactor 1 (Methanol Synthesis): Syngas is fed to Reactor 1, the first of four reactors, which converts most of the syngas (CO and H2) to methanol (CH3OH) when passing through the catalyst bed.
Reactor 2 (Dimethyl Ether Synthesis): The methanol-rich gas from Reactor 1 is next fed to Reactor 2, the second STG+ reactor. The methanol is exposed to a catalyst and much of it is converted to dimethyl ether (DME), which involves a dehydration from methanol to form DME (CH3OCH3).
Reactor 3 (Gasoline Synthesis): The Reactor 2 product gas is next fed to Reactor 3, the third reactor containing the catalyst for conversion of DME to hydrocarbons including paraffins (alkanes), aromatics, naphthenes (cycloalkanes) and small amounts of olefins (alkenes), mostly from C6-C10.
Reactor 4 (Gasoline Treatment): The fourth reactor provides transalkylation and hydrogenation treatment to the products coming from Reactor 3. The treatment reduces durene (tetramethylbenzene)/isodurene and trimethylbenzene (TMB) components that have high freezing points and must be minimized in gasoline. As a result, the synthetic gasoline product has high octane and desirable viscometric properties.
Separator: Finally, the mixture from Reactor 4 is condensed to obtain gasoline. The non-condensed gas and gasoline are separated in a conventional condenser/separator. Most of the non-condensed gas from the product separator becomes recycle gas and is sent back to the feed stream to Reactor 1, leaving the synthetic gasoline product comprising paraffins, aromatics and naphthenes.
Baliban, R. C.; Elia, J. A.; Floudas, C. A. (2013) Biomass to liquid transportation fuels (BTL) systems: process synthesis and global optimization framework. Energy & Environmental Science 6, 267-287 doi: 10.1039/C2EE23369J
Richard C. Baliban, Josephine A. Elia, Christodoulos A. Floudas, Barri Gurau, Michael B. Weingarten, and Stephen D. Klotz (2013) Hardwood Biomass to Gasoline, Diesel, and Jet Fuel: 1. Process Synthesis and Global Optimization of a Thermochemical Refinery. Energy & Fuels doi: 10.1021/ef302003f
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