Effect of Biodiesel Components on Cetane Number and Lubricity

Kapila WadumesthrigeNBEL

Department of Chemical EngineeringWayne State University

Biodiesel Composition• Methyl esters of long chain fatty acids• > 98 % FAME• < 2% of other components

– Free Glycerin– Mono, di and tri glyceride– Antioxidants– Sterols– Phospholipids– Water

Biodiesel properties

• High calorific value – FAME

• Oxidation stability- unsaturation/ antioxidants

• Cold flow properties- chain length/ saturation /sterols ?

• Ignition quality – oxygenated/ minor components

• Lubricity – FAME/ FFA/other?

Effect of composition on biodiesel Ignition Quality

ASTM test D-6890 -using IQT

DCN = 83.99(ID-1.512) -0.658 + 3.547

• measure of the ignition quality of diesel fuel via the compression ignition process.

• is actually a measure of a fuel's ignition delay• Ignition Delay-the time period between the start of

injection and start of combustion• Diesel fuels with required Cetane number improve

– cold starting, reduce smoke during start up– improve fuel economy, reduce exhaust emissions, – reduce noise and vibration, improve engine

durability

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Soy Bean Cotton Seed Poultry Fat YellowGrease

ULSD

Fuel Type

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Derived Cetane Number (DCN) of biodiesel

EN standard

US standard

Biodiesel samples stored under ambient conditions

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Soy BD Cotton Seed Poultry Fat Yellow Grease

Stored at room temp Stored at 4 C Distilled

DCN of biodiesel at various conditions

Distilled biodiesel contains only FAMEDCN variation of distilled BD due to FAME composition

Name 10 min 30 min 60 min 120 minAmbient Oxidation

C14:0 0.87 0.91 0.78 0.90 0.70

C16:0 24.81 24.89 24.39 24.83 25.27

C16:1 0.31 0.32 0.45 0.31 0.36

C18:0 2.50 2.50 2.47 2.43 2.36

C18:1 18.27 17.96 18.10 17.99 18.61

C18:2 52.84 52.47 52.06 52.30 48.47

C18:3 0.00 0.00 0.00 0.00 0.00

C20:0 0.00 0.00 0.00 0.00 0.00

FAME % 99.60 99.06 98.25 98.76 95.76

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Reaction time (min)

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DCN Conductivity

FAME composition (%) of oxidized cotton seed biodiesel

Oxidation of Distilled Cotton Seed BD Vs. Cetane number

Oxidation at 110 C, 10 L/min Air

• Cetane number of BD depends on chemical composition of FAME,

• amount of trace compounds • secondary products due to oxidation of FAMEs.

Effect of major and minor components of biodiesel on petroleum and synthetic fuel

• Quality that prevents wear when two moving metal parts come in contact with each other.

• Desulphurization reduces the inherent lubricity of diesel• Adding bio diesel at low levels (1-2%) increase the lubricity of

low sulfur diesel.

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0 1 2 3 4 5Concentration of Biodiesel in ULSD (v/v%)

HFR

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Cotton-ULSD Soy-ULSD Poultry-ULSD

Soy-S8 Cotton-S8 Poultry-S8

•Lubricity increases sharply as BD blending level increase then levels off at ~2% limit.

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C 18:2 Glycerol Tocopherol Soy Biodiesel Refined Soy Refined Soy +Palmatic Acid

Type of Additive (2 % v in ULSD)

% L

ub

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eLubricity of Refined Soy Biodiesel

Acid numbers; Soy BD = 0.25, Refined Soy BD = 0.19 Palmatic acid equal to 0.06 Acid # added to refined Soy BD

•Lubricity increases sharply as BD blending level increase then levels off at ~2% limit.•BD lubricity is due to combination of major and minor components