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Several diesel formulations were evaluated for the engine manufacturers association (EMA) by MathPro.  This analysis included a range of sulfur levels for on-road, off-road, and light-duty diesel fuel.  The very low sulfur diesel formulation (20 ppm sulfur) was selected to represent reformulated diesel in California.  The properties of other diesel formulations included in the EM study are also shown.

Table 2-2:  Diesel Fuel Properties

Fuel

RVPa

(psi)

Aromatics

(wt %)

Sulfur

(ppm wt)

Cetane Index

API Gravity

Low aromatics dieselb

0.03

8.3

60

50

39.7

Diesel, alternate formulationb

0.03

27.8

250

55.3

33.8

Very low sulfur diesel (RFD)c

0.03

30.5

20

47.8

36.5

150 ppm dieseld

0.03

30.5

150

47.4

36.2

FT diesel

0.03

0.0

0.0

75

45

aRVP = Reid vapor pressure (EPA AP-42).

bSamples from fuel sold in California in 1994, Unnasch 1994.

cProperties from MathPro Case 8.

dProperties from MathPro Case 9a.

The properties of diesel fuel for this study are shown in Table 2-2.  RVP values for diesel are not frequently measured.  EPA's document on emission factors from stationary sources (EPA AP-42) shows true vapor pressures for diesel fuel as a function of fuel temperature.  The heating value and density of the very low sulfur and low aromatics formulation are consistent with higher hydrogen content in the fuel (shown in Table 2-1).

2.1.2  LPG

The composition of LPG represents typical analyses of fuel collected in Southern California (Unnasch 1994).  Propane and butanes produced in oil refineries are now mostly converted to alkylate, used in the production of ethers, or sold into the chemical market; however, this LPG could be diverted to a higher value fuel market.  Petroleum-based LPG contains several percent propylene while natural gas based LPG contains no propylene or other olefins.  LPG compositions from petroleum and natural gas are shown in Table 2-3.

The propylene (C3H6) content of the LPG samples in Table 2-3 indicates that one sample was largely from petroleum-derived sources and another sample was derived from natural gas.  The majority of this sample came from an oil refinery. ARB's specification limits propylene to a maximum of 5 percent; however, observations of propylene in commercial LPG have shown lower levels.  LPG is stored in pressure vessels.  At 100F the vapor pressure is about 190 psi.

2.1.3  Synthetic Diesel

10

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