Robert L. McCormick

Combustion of fat and vegetable oil derived fuels in diesel engines

In this article, the status of fat and oil derived diesel fuels with respect to fuel properties, engine performance, and emissions is reviewed. The fuels considered are primarily the methyl esters of fatty acids derived from a variety of vegetable oils and animal fats, and referred to as biodiesel. The major obstacle to widespread use of biodiesel is the high cost relative to petroleum. Economics of biodiesel production are discussed, and it is concluded that the price of the feedstock fat or oil is the major factor determining biodiesel price.Biodiesel is completely miscible with petroleum diesel fuel, and is generally tested as a blend. The use of biodiesel in neat or blended form has no effect on the energy based engine fuel economy. The lubricity of these fuels is superior to conventional diesel, and this property is imparted to blends at levels above 20 vol%. Emissions of PM can be reduced dramatically through use of biodiesel in engines that are not high lube oil emitters. Emissions of NOx increase significantly for both neat and blended fuels in both two- and four-stroke engines. The increase may be lower in newer, lower NOx emitting four-strokes, but additional data are needed to confirm this conclusion. A discussion of available data on unregulated air toxins is presented, and it is concluded that definitive studies have yet to be performed in this area. A detailed discussion of important biodiesel properties and recommendations for future research is presented. Among the most important recommendations is the need for all future studies to employ biodiesel of well-known composition and purity, and to report detailed analyses. The purity levels necessary for achieving adequate engine endurance, compatibility with coatings and elastomers, cold flow properties, stability, and emissions performance must be better defined.

Preparation and characterization of Pd-Cu composite membranes for hydrogen separation

Pd–Cu composite membranes were made by successive electroless deposition of Pd and then Cu onto various tubular porous ceramic supports. Ceramic filters used as supports included symmetric -alumina (nominal 200 nm in pore size), asymmetric zirconia on-alumina (nominal 50 nm pore size), and asymmetric -alumina on -alumina (nominal 5 nm pore size). The resulting metal/ceramic composite membranes were heat-treated between 350 and 700 ◦ C for times ranging from 6 to 25 days to induce intermetallic diffusion and obtain homogeneous metal films. Pure gas permeability tests were conducted using hydrogen and nitrogen. For an 11 m thick, 10 wt.% Cu film on a nominal 50 nm pore size asymmetric ultrafilter with zirconia top layer, the flux at 450 ◦ C and 345 kPa H2 feed pressure was 0.8 mol/m 2 s. The ideal hydrogen/nitrogen separation factor was 1150 at the same conditions. The thickness of the metallic film was progressively decreased from 28 md own to 1–2m and the alloy concentration was increased to 30 wt.% Cu. Structural factors related to the ceramic support and the metallic film chemical composition are shown to be responsible for the differences in membrane performance. Among the former are the support pore size, which controls the required metal film thickness to insure a leak-free membrane and the internal structure of the support (symmetric or asymmetric) which changes the mass transfer resistance. The support with the 200 nm pores required more Pd to plug the pores than the asymmetric membranes with smaller pore sizes, as was expected. However, leak-free films could not be deposited on the support with the smallest pore size (5 nm -alumina), presumably due to surface defects and/or a lack of adhesion between the metal film and the membrane surface.

Diesel and CNG Transit Bus Emissions Characterization By Two Chassis Dynamometer Laboratories: Results and Issues

Emissions of six 32 passenger transit buses were characterized using one of the West Virginia University (WVU) Transportable Heavy Duty Emissions Testing Laboratories, and the fixed base chassis dynamometer at the Colorado Institute for Fuels and High Altitude Engine Research (CIFHAER). Three of the buses were powered with 1997 ISB 5.9 liter Cummins diesel engines, and three were powered with the 1997 5.9 liter Cummins natural gas (NG) counterpart. The NG engines were LEV certified. Objectives were to contrast the emissions performance of the diesel and NG units, and to compare results from the two laboratories. Both laboratories found that oxides of nitrogen and particulate matter (PM) emissions were substantially lower for the natural gas buses than for the diesel buses. It was observed that by varying the rapidity of pedal movement during accelerations in the Central Business District cycle (CBD), CO and PM emissions from the diesel buses could be varied by a factor of three or more. The driving styles may be characterized as aggressive and non-aggressive, but both styles followed the CBD speed command acceptably. PM emissions were far higher for the aggressive driving style. For the NG fueled vehicles driving style had a similar, although smaller, effect on NO{sub x}. It is evident that driver habits may cause substantial deviation in emissions for the CBD cycle. When the CO emissions are used as a surrogate for driver aggression, a regression analysis shows that NO{sub x} and PM emissions from the two laboratories agree closely for equivalent driving style. Implications of driver habit for emissions inventories and regulations are briefly considered.

Idle Emissions from Heavy-Duty Diesel and Natural Gas Vehicles at High Altitude

ABSTRACT Idle emissions of total hydrocarbon (THC), CO, NOx, and particulate matter (PM) were measured from 24 heavy-duty diesel-fueled (12 trucks and 12 buses) and 4 heavy-duty compressed natural gas (CNG)-fueled vehicles. The volatile organic fraction (VOF) of PM and aldehyde emissions were also measured for many of the diesel vehicles. Experiments were conducted at 1609 m above sea level using a full exhaust flow dilution tunnel method identical to that used for heavy-duty engine Federal Test Procedure (FTP) testing. Diesel trucks averaged 0.170 g/min THC, 1.183 g/min CO, 1.416 g/min NOx, and 0.030 g/min PM. Diesel buses averaged 0.137 g/min THC, 1.326 g/min CO, 2.015 g/min NOx, and 0.048 g/min PM. Results are compared to idle emission factors from the MOBILE5 and PART5 inventory models. The models significantly (45-75%) overestimate emissions of THC and CO in comparison with results measured from the fleet of vehicles examined in this study. Measured NOx emissions were significantly higher (30-100%) than model predictions. For the pre-1999 (pre-consent decree) truck engines examined in this study, idle NOx emissions increased with Health and Environment; June 30, 1999 (available from the authors).

Effect of Humidity on Heavy-Duty Transient Emissions from Diesel and Natural Gas Engines at High Altitude

Abstract The Code of Federal Regulations (CFR 40 Part 86 Subpart N) defines a universal humidity correction for NOx emissions from heavy–duty diesel and alternative fueled engines measured by the heavy–duty transient test. This testing procedure and humidity correction apply to any heavy–duty engine subject to regulation of particulate matter emissions, including spark ignited engines. This correction has been evaluated for a 1988 Detroit Diesel Series 60 engine and a 1995 Cummins B5.9G natural gas engine. The correction at high altitude for the diesel engine is in excellent agreement with the correction published in the Code of Federal Regulations. In addition, humidity is found to affect particulate matter in agreement with the Engine Manufacturers Association correction factor. This suggests that these results, acquired at high altitude, are generally applicable to all altitudes. CO emissions are also correlated with humidity. Emission traces show that humidity affects NOx uniformly for the diesel engi...

Methane partial oxidation by silica‐supported iron phosphate catalysts. Influence of iron phosphate content on selectivity and catalyst structure

Selective oxidation of methane to methanol and formaldehyde at atmospheric pressure was studied over a series of silica‐supported FePO4 catalysts, with iron phosphate content ranging from 2 to 16 wt%. Performance was evaluated over the range T=773–963 K, GHSV=25,000–65,000 h−1, and CH4 : O2=1. The main products were formaldehyde, carbon monoxide and carbon dioxide. Small, but quantifiable amounts of methanol were also observed. Catalytic activity exhibited a clear dependence on the iron phosphate content. The highest selectivity and space time yield (STY) to formaldehyde and methanol were observed for 2 wt% FePO4 on silica (STY of 622 and 25 g/kgcat h, respectively). The selectivity–conversion pattern suggests that methane is oxidized directly to methanol and formaldehyde, and sequentially to carbon oxides. Characterization was performed by X‐ray powder diffraction, X‐ray photoelectron spectroscopy, and Mössbauer spectroscopy. Crystalline FePO4 is observed at all loading levels, however, a significant fraction of the iron (58% at 2 wt% FePO4) is present in an X‐ray amorphous phase. Mössbauer spectra suggest that this phase contains iron in five‐fold coordination, and with a higher electron density relative to bulk FePO4. The amount of this five‐coordinate phase present is roughly 1 wt% Fe, independent of total iron loading. XPS confirms the lower effective oxidation state of iron, and indicates that at low loading the surface is enriched in phosphorus relative to bulk FePO4. It is proposed that iron in five‐fold coordinate sites, isolated by phosphate groups, more selectively activates methane than crystalline FePO4. As loading increases, so does the amount of crystalline FePO4, which is proposed to more rapidly catalyze sequential oxidation of the selective products.

PALLADIUM/COPPER ALLOY COMPOSITE MEMBRANES FOR HIGH TEMPERATURE HYDROGEN SEPARATION FROM COAL-DERIVED GAS STREAMS

For hydrogen from coal gasification to be used economically, processing approaches that produce a high purity gas must be developed. Palladium and its alloys, nickel, platinum and the metals in Groups 3 to 5 of the Periodic Table are all permeable to hydrogen. Hydrogen permeable metal membranes made of palladium and its alloys are the most widely studied due to their high hydrogen permeability, chemical compatibility with many hydrocarbon containing gas streams, and infinite hydrogen selectivity. Our Pd composite membranes have demonstrated stable operation at 450 C for over 70 days. Coal derived synthesis gas will contain up to 15000 ppm H{sub 2}S as well as CO, CO{sub 2}, N{sub 2} and other gases. Highly selectivity membranes are necessary to reduce the H{sub 2}S concentration to acceptable levels for solid oxide and other fuel cell systems. Pure Pd-membranes are poisoned by sulfur, and suffer from mechanical problems caused by thermal cycling and hydrogen embrittlement. Recent advances have shown that Pd-Cu composite membranes are not susceptible to the mechanical, embrittlement, and poisoning problems that have prevented widespread industrial use of Pd for high temperature H{sub 2} separation. These membranes consist of a thin ({le} 5 {micro}m) film of metal deposited on the inner surface of a porous metal or ceramic tube. With support from this DOE Grant, we have fabricated thin, high flux Pd-Cu alloy composite membranes using a sequential electroless plating approach. Thin, Pd{sub 60}Cu{sub 40} films exhibit a hydrogen flux more than ten times larger than commercial polymer membranes for H{sub 2} separation, resist poisoning by H{sub 2}S and other sulfur compounds typical of coal gas, and exceed the DOE Fossil Energy target hydrogen flux of 80 ml/cm{sup 2} {center_dot} min = 0.6 mol/m{sup 2} {center_dot} s for a feed pressure of 40 psig. Similar Pd-membranes have been operated at temperatures as high as 750 C. We have developed practical electroless plating procedures for fabrication of thin Pd-Cu composite membranes at any scale.

7 – Exhaust Emissions

Publisher Summary This chapter discusses impacts of biodiesel fuel on pollutant emissions from diesel engines and ultrafine particles from a heavy duty diesel engine running on rapeseed oil methyl ester. An important benefit of biodiesel has been its ability to reduce Particulate Matter (PM) emissions. PM includes soot carbon, unburned fuel, lube oil, and sulfuric acid aerosols and it is often fractionated in terms of sulfate, Soluble Organic Fraction (SOF) or Volatile Organic Fraction (VOF), and carbon or soot. Biodiesel can impact soot and SOF originating from the fuel but not SOF originating from the lubricant. Because biodiesel from many sources contains essentially no sulfur, blending biodiesel into diesel fuel can reduce sulfate emissions. Diesel engines are significant contributors of NOx and PM to air pollutant inventories. Although emission standards for NOx and PM have been significantly reduced since 2000, diesel vehicles remain a significant source of these two pollutants. The impact of biodiesel on NOx and PM emissions is the primary concern of the chapter. Biodiesel and biodiesel blends reduce total emissions of various classes of toxic compounds. PM is recognized as one of the major harmful emissions generated by the use of diesel engines; therefore, it is subject to exhaust engine emission regulations worldwide. Besides engineering parameters, such as design of the combustion chamber and the injection system, the mode of operation, or rather the overall load configuration, the fuel and lubricant quality, as well as the wear of the engine affect PM composition. Recently, exhaust emissions of fine and ultrafine particles from diesel engines caused an extensive discussion in Europe.