pp54

PP54 Rev A

of 4 COPYRIGHT, 2009, GE PACKAGED POWER, L.P.,ALL RIGHTS RESERVED. THIS DRAWING IS THE PROPRIETARY AND/OR CONFIDENTIAL PROPERTY OF GE

PACKAGED POWER, L.P., AND IS LOANED IN STRICT CONFIDENCE WITH THE UNDERSTANDING THAT IT WILL NOT BE REPRODUCED NOR USED FOR ANY PURPOSE

EXCEPT THAT FOR WHICH IT IS LOANED. IT SHALL BE IMMEDIATELY RETURNED ON DEMAND, AND IS SUBJECT TO ALL OTHER TERMS AND CONDITIONS OF ANY

WRITTEN AGREEMENT OR PURCHASE ORDER WHICH INCORPORATES OR RELATES TO THIS DRAWING.

.

Use of Biodiesel in the LM Packages

Introduction

The use of biofuels in the LM packages is becoming more prevalent in the industry today. This position paper addresses one of biofuels in particular, biodiesel. Biodiesel is another name for a ‘fatty acid methyl ester’ (FAME) that is man made from reacting a fatty acid with methanol. The fatty acid is a plant (jatropha, rapeseed, palm, algae, etc.) or animal fat by product; all having a varied amount of C14-C22 saturated and unsaturated fatty acids in them. This paper will attempt to address LM packaging concerns when using this fuel.

Description

Biodiesel is defined as the monoalkyl esters of long chain fatty acids derived from vegetable oils, waste cooking oils, or animal fats. Fatty acid oil methyl esters (FAMEs) are made by transesterifcation in the presence of a catalyst (usually a base) with alcohol (usually methanol) to form methyl esters and glycerine as a byproduct. Biodiesel contains practically no sulfur and no aromatics (toluene, benzene, etc.) and has a much narrower compound distribution than diesel. Biodiesel also has its own ASTM Specification, ASTM D6751, and European Specification EN 14214.

Diesel made from crude oil (petrodiesel) is a mixture of hydrocarbons, while biodiesel is a mixture of unsaturated fatty acid esters. The concern of this paper arises from the fact that petrodiesel and biodiesel have such different chemical structures and consequent different effects on elastomers commonly found in many of the gaskets and sealants in a typical LM package. Biodiesel is a much better solvent that the petrodiesels, and thus affects sealing materials differently. While there are ‘other’ properties of biodiesel that must be addressed, none affects the LM package more than its effect on the gaskets and sealants. There has been much research on the effects of biodiesel and the blends of biodiesel with petrodiesels that has influenced the conclusions of this paper. One of the better qualities of biodiesel is its lubricity, and it can actually be used as an additive to improve the lubricity of most fossil fuels; especially those that have ultra-low sulfur. It also burns cleaner and creates about 60% less net carbon dioxide emissions in diesel engines1. These ‘diesel’ fuel specifications, ASTM D396 and ASTM D975,

GE Energy Aero Energy Division

Position Paper #54

Rev A

Date: March 9, 2009

16415 Jacintoport Blvd

Houston, TX 77015

USA T 001-281-864-2543

F 001-281-864-2459

PP54 Rev A





have recently been revised to include up to 5% blended biodiesel in diesels #1 and #2. This revision means that our LM packages could be seeing a biodiesel fuel flow even today. While lubricity is a plus for biodiesel and biodiesel blends, material compatibility may be a problem. Based on fluorohydrocarbon elastomers (like Viton) research, GE Aero is considering upgrading its sealing gaskets and o-rings to a more robust form of Viton to head off future package sealing problems. There is no long term data available for this issue because biodiesel is fairly new to the market, but accelerated testing has allowed researchers to see what may happen over time. Viton and Teflon, two biodiesel compatible sealants, are already used in our LM product packages. Teflon has been shown to be fairly resistant to the solvent properties of biodiesel and presents no issues as it is. Viton, on the other hand, is better or worse depending on how it was cured. Metal oxide or hydroxide cured Viton has been improved in recent years by peroxide curing, but metal oxides are still added in excess at the end of the reaction to facilitate cure efficiency and promote thermal stability. Research has shown, however, that the presence of any metal oxides can cause biodiesel breakdown (breaks back down to its original components). The original components of biodiesel then are thought to cause the Viton deterioration.1 Research has also shown that the presence of water in the biodiesel or biodiesel/diesel blends affects the life and resiliency of Viton. Biodiesels are more hydroscopic than diesel, so they will always retain more water than diesel; water that is not normally separated via centrifuging or settling. Another chemical anomaly of biodiesel is that it can change with age; meaning, if not used quickly, it can ‘sour’ or begin to separate back into its starting components. The presence of even small amounts of water and time can cause a reverse reaction (breaking the ester back into its acid and alcohol components) resulting in a product that has been shown to be more aggressive towards sealants than fresh biodiesel. Swelling or volume change has long been used as a measure of sealant resiliency. There are other measures such as hardness and stress-strain changes, but swelling is most important from a possible leakage standpoint. The more the sealant swells with one liquid, the more likely it is to leak with another that does not cause it to swell as much. Swelling is the most pronounced result of biodiesel on metal containing Vitons. Vitons that are neither made with metal oxides nor cured with metal oxides are the Vitons that GE Aero is considering using in its liquid fuel systems for fuels containing greater than 5% biodiesel. Dupont makes a line of products that are called non (or no)-metal oxide (NMO) Vitons. A kit was put together by the Fuels Group that would change out certain gaskets, seals, and o-rings when a CM&U fuel conversion to biodiesel is made for the LM6000 product line. The chart below is data taken from a DuPont Peformance Elastomers report published in 2007. The chart is for various Vitons soaked in straight biodiesel (B100), that has water added to it, and it has been setting for a period of time (aged); pretty much a worse case scenario for biodiesel. The first 2 Vitons to the left, which are called NMO, are non-metal oxide Vitons, while the 3 on the right either have been cured with metal

PP54 Rev A





oxides or made with metal oxides. This test was also conducted at 125 C which is equivalent to ~257 F. The chart indicates that the NMO Vitons are not apt to change even under these harsh conditions. There is other research data that shows similar results for B5 and B20 biodiesels (5% and 20% biodiesel in diesel).

From “Fluoroelastomer Compatibility with BioDiesel Fuels”, Eric W. Thomas, Robert E. Fuller, and Kenji Terauchi, Dupont Performance Elastomers LLC

Conclusion Biodiesel has already been used in the LM2500 marine units, and tested in the LM6000 as B100. The results of its use have been encouraging and there is increased interest to use more and more of these biofuels to make power. GE Aero will continue to see biodiesel in blends as states and countries strive to meet carbon friendly mandates.

Based on the research that has been done up to now on the effects of biodiesel on metal oxide containing Viton, GE Aero is considering the use of only NMO Viton (no need to change out Teflon parts) for biodiesel blends greater than B5. B5 is recognized in the industry as diesel. Also under consideration are the liquid fuel system components (metering valves, fuel valves, RTDs, etc.); making sure that they are biodiesel compatible and are warranted as such. 1.“Fluoroelastomer Compatibility with BioDiesel Fuels”, Eric W. Thomas, Robert E. Fuller, and Kenji

Terauchi, Dupont Performance Elastomers LLC; 2007-01-4061

PP54 Rev A





pp54

Documents

Transcript of pp54