South Coast Air Quality Management District

Issue RFP for Development and Demonstration of Fischer-Tropsch Fueled Heavy-Duty Vehicles with Control Technologies for Reduced Diesel Exhaust Emissions

SYNOPSIS:

On-road heavy-duty diesel vehicles are subject to emission standards of 0.01 g/bhp-hr PM, effective 2007 and 0.20 g/bhp-hr NOx to be phased in between 2007 and 2010. To meet these targets, an effective diesel emission control strategy must employ advanced fuels, engine design features, improved exhaust gas recirculation (EGR) systems, and aftertreatment devices that are optimized using a systems approach. The proposed RFP solicits cost-shared proposals to develop and test prototype heavy-duty vehicles fueled by Fischer-Tropsch fuel to evaluate the performance and emission-reduction potential of these advanced emission control systems. Cost to the AQMD for the proposed $1.2 million project shall not exceed $350,000. CEC contributes $400,000, while DOE will provide $300,000 and $150,000 in direct cash and in-kind contributions, respectively.

COMMITTEE:

Technology, September 28, 2001, Recommended for Approval

RECOMMENDED ACTION:

Approve release of RFP #P2002-18 to solicit cost-shared proposals to develop and test modified heavy-duty vehicles fueled by Fischer-Tropsch fuel, to evaluate emission-reduction potential and reliability of diesel emission control technologies, in an amount not to exceed $350,000 from the Clean Fuels Fund (Fund 31).

Barry R. Wallerstein, D.Env.
Executive Officer

Background

The U.S. EPA has recently established a federal standard for on-road heavy-duty diesel vehicles of 0.01 grams per brake-horsepower-hr (g/bhp-hr) PM, effective 2007, and 0.20 g/bhp-hr NOx to be phased in between 2007 and 2010. In response to these tighter emission standards, engine manufacturers have improved or are improving their engine designs through electronic engine controls, changes in fuel injection systems, handling of intake air, combustion chamber modification, exhaust gas recirculation systems, and reducing oil consumption. Although these engine improvements have shown some emission-reduction potential, more work is needed to meet future emission standards. Additionally, several thermal and catalyzed technologies have been developed to control diesel NOx and PM emissions, but many of these systems are in the early stages of laboratory development and have not been tested in diesel vehicles. Even the potentially promising technologies have development challenges, and require diesel fuel with sulfur content below 10 ppm in general to be commercially viable in heavy-duty diesel applications.

The AQMD, U.S. Department of Energy’s (DOE) National Renewable Energy Laboratory (NREL), and California Energy Commission (CEC) are exploring an alternative diesel emission control strategy, which could reduce on-road heavy-duty diesel NOx and PM exhaust emissions by 60 and 90 percent or more, respectively. These emission reductions may be achieved without significantly increasing fuel consumption on an energy equivalent basis. Specifically, this alternative strategy uses Fischer-Tropsch (F-T) synthetic diesel fuel, which has outstanding ignition qualities, is sulfur free, and may enable the use of advanced emission control technologies that may not otherwise be possible with conventional diesel fuels.

Introduction

F-T fuels, named after 1920’s synthetic-fuel researchers Franz Fischer and Hans Tropsch, have not been widely used in the U.S., but have been blended with crude-oil-derived fuels in California to meet CARB standards. F-T fuels are produced from a variety of sources, including natural gas, coal or biomass through a commercial gas-to-liquid process utilizing catalysts at high pressures. There are currently three commercial F-T fuel plants operating in the world, Sasol and Mossgas in South Africa and the Shell Bintulu plant in Malaysia. Sasol produces 170,000 barrels per day (bbl/day), Mossgas 30,000, and Shell 12,500 bbl/day. An additional F-T fuel plant with a capacity of 40,000 bbl/day (about one-quarter of current demand) is planned in Alaska, and many major refiners have announced plans to build pilot or commercial F-T fuel plants.

F-T fuels are characterized as having a high cetane number, and very low sulfur and aromatic content. Because F-T fuel characteristics are an improvement over those of traditional diesel fuels, many tests were conducted to assess emission-reduction potential and durability of these fuels in unmodified heavy-duty diesel trucks and buses. These tests¹²³ show that neat F-T fuels combust more cleanly, and produce lower engine-out emissions of NOx (>6%), VOC, PM (>24%), and carcinogenic pollutants than CARB diesel fuel. Even greater emissions reductions may be realized with F-T fuel because: 

-	Engine and emission control systems can be optimized for use with Fischer-Tropsch diesel fuel by modifying the combustion system. Since F-T diesel has a high cetane number, changes to the injection timing, compression ratio, and EGR rate can be made that would not otherwise be possible with conventional diesel fuels.
-	Aftertreatment NOx and PM control devices can be used without being overly concerned about high sulfur content negatively affecting the durability and effectiveness of the control device. Moreover, some types of aftertreatment devices may have higher emission conversion efficiencies when used with F-T fuels.

A research project funded by DOE⁴ recently demonstrated that a systems approach—advanced fuels, improved combustion, and state-of-the-art catalyst systems—can greatly reduce regulated emissions without significantly compromising fuel consumption. A model year 2000 Power Stroke 7.3 liter turbocharged diesel engine was modified to take advantage of the properties of F-T fuel. This strategy⁴ combines engine modifications (geometrical changes in piston bowl), with improved EGR systems, two-stage lean NOx catalyst, catalyzed particulate trap, and F-T fuel to achieve significant engine-out NOx (97%) and PM (94%) emissions reduction. This positive result forms the basis for this proposal. Since these technologies are all production viable, it is anticipated that an advanced engine system could be further developed in the engine laboratory and subsequently installed and demonstrated in prototype vehicles. Additionally, it is anticipated that if the proposal were successful, NOx and PM emissions reduction could be achieved in the near-term since the elements of the control strategy are commercially available.