Emulsified Fuels: Improved Combustion of Heavy Oils ... MEPEC Seth Ellis Grimes_201111a.… ·...

Copyright © 2011: Alternative Petroleum Technologies S.A.

Emulsified Fuels: Improved Combustion of Heavy Oils & Emission Control for Sustainable Fuels

At MEPEC 2011 by

Jyoti Seth, Richard Ellis, and Patrick Grimes

Alternative Petroleum Technologies Inc. www.altpetrol.com 1


● Biodiesel in Engines

● Emission impact of Biodiesel and Biodiesel blends in light of emission norms

● Emulsified Biodiesel as solution for disadvantages of combusting neat biodiesel

● Heavy Fuel Oil in Furnaces

● Increased heavies content and contamination in tanks or during distribution

● Traditional approaches for effectively combusting heavier oil

● Emulsified fuels for improved efficiencies, lower emissions and cleaner operations

2


● Biodiesel can be made from a wide variety of bio-fuel feedstock as well as a range of biodiesel-diesel contents depending on its intended use.

● There is however the problem of elevated NOX emissions from biodiesel, exemplified in this EPA graph showing NOX increasing with the concentration of biofuel.

3

Per

cent

cha

nge

in N

Ox

Em

issi

ons


0.1 -

0.001 -

0.01 -

10 1 0.1 0.01

TIER 3 US 2004

US 2

004

EURO III

EURO

III

EURO

IV

EURO

V

TIER

4

US 2

007

/ 10

PM [g

/kW

h]

NOx [g/kWh]

Diesel 13% Emulsion

Reference: SAE 2003-01-3146. Influence of Water-Diesel Emulsions and EGR on Combustion and Exhaust Emissions of Heavy Duty DI-Diesel Engines equipped with Common-Rail Injection System. Bertola, A; Li, R, Boulouchos, K.

4


● The rule of thumb is that for every 1% water NOx is reduced by 1% and PM by 2%. In fact the value of a percent of water is far greater at low water content for both diesel (B0) and B20.

1.70

0.69

0.15 0.25

1.15

0.24 0.32

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

0 5 10 15 20 25

NO

x R

educ

tion

(%R

educ

tion/

%m

wat

er)

%m Water

NOx Reduction (% Reduction per % water)

B0 B20 5.89

4.08

1.31 0.70

4.68

2.33

0.12 0

1

2

3

4

5

6

7

0 5 10 15 20 25

PM R

educ

tion

(%R

educ

tion/

%m

wat

er)

%m Water

PM Reduction (% Reduction per % water)

B0 B20

5


● Requires -

● Atomization – combustion time

● Fuel-Air ratio – turbulence and mixing

● Flame temperature

Dust & Smoke

Dust is generated when oil is vaporized

but not combined with oxygen

Small carbon particles which are incompletely combusted, gather up

and become smoke, etc.

100-200 µm Heat of Combustion

Evaporative Combustion

6


Parameters/Properties Units IS-1593 max FO sample Recent Trends

i. CCR (residual carbon) % mass 4.0 max 16.11

ii. Asphaltene / tar content % mass - 6.8

iii. Moisture Content % mass 1 max 0.29 Contamination

iv. Sediment % mass 0.25 max 0.03

v. Viscosity @50 degree cSt 250 max 204.3 -

vi. Viscosity @90 degree C cSt - 36.6 -

viii. Sulphur content % mass 4.5 max 3.5 -

ix. Density (@ 15 deg C) g/cc - 0.9761

x. Gross Calorific Value cal/g - 10820 -

Recent years have seen deteriorating quality of furnace oil

7


● Higher viscosity – Affects fuel atomization and hence larger fuel droplets

0.1

1

10

100

1000

1 10 100 1000

Tim

e, t

(ms)

Droplet Size, d (m)

20 ms

68 ms

1.7dt ∝

200 µ

INSUFFICIENT TIME & higher un-burnt residues and increased fouling

8


● Complete combustion needs sufficient Time, Temperature, and Turbulence

● Heavier components such as Asphaltenes, etc. are more viscous and require higher combustion temperature

● Un-burnt carbon and dust accumulate as slag and lead to fouling of boiler furnace and tubes and performance deterioration

0

2

4

6

8

10

0 0.5 1 1.5 2 2.5 3 3.5

Loss

of e

ffici

ency

(%)

Soot Layer Thickness (mm)

9


● To avoid incomplete combustion and un-burnt carbon residue, users operate at high excess air for better mixing and TURBLUENCE

● Lower flame temperature and high stack losses impact efficiency

● Water in oil emulsions aid problems arising due to incomplete combustion

1600

2000

2400

0 2 4 6 8

AFT,

deg

. K

% Excess Oxygen

10


● Emulsion Fuels are not new. When two immiscible fluids, oil and water are sheared together in the presence of a surfactant additive, a stable emulsion can be produced.

Water

Fuel

Additive High Shear

You need (1) enough energy and (2) good chemistry.

Water in OIL

11


● Modifications to boilers

● No modifications are necessary

● Protocols for “fuel switching” involve:

● Ensuring storage and recirculation temperatures don’t exceed 100C; and

● Adjusting excess air to for improvement atomization

● Reduction in NOx, enhanced combustion efficiency and lower PM

12


● Micron sized droplets of water initiate secondary atomization and fuel is shattered to fine and turbulent mist of smaller droplets in air

● Improved turbulent mixing and virtually eliminates smoke

13


● At 10% water in oil:

● Theoretical flame temperature (AFT) reduced by 0.65 %

1950

1970

1990

2010

2030

2050

2070

0 5 10 15 20 25

Adia

batic

Fla

me

Tem

p. (K

)

Emulsion Water Content (%)

(-28 K)

(-13 K)

14

Base Fuel


● 10% water in oil is commensurate to

● Small increase in water content of flue gas stream (by 8.5 %)

● Low excess air levels are possible with emulsions

● Small trimming of excess air (6.8 %) is sufficient to off-set temperature reduction due to water

3.0

3.5

4.0

4.5

5.0

5.5

5

6

7

8

9

10

0 5 10 15 20 25

% E

xces

s O

xyge

n

% M

oist

ure

in F

lue

Gas

Emulsion Water Content (%)

(-0.16) (-0.34)

(0.26) (0.54)

15


● Relative contributions of

● added water in fuel and

● reduced excess air

● impact following parameters and hence the heat transfer dynamics:

Parameter Water Addition Air Reduction Combined

Flame T

Flame Emissivity

Radiation Heat

Reynolds No -

Prandtl No -

Heat Transfer Coefficient -

Un-burnt HC

Efficiency

16


● While efficiency increases with lesser excess oxygen, For every % water, efficiency is reduced by 0.13%

● Efficiency will increase by switching from base fuel operation at 5% to 2.5% excess oxygen efficiency increases from 83.5% to 84.3%

● With scope for further increase through even lower excess O2 and improved combustion

17


● Performance of emulsified fuel oil shows improvement over baseline fuel oil

13.4

13.6

13.8

14.0

14.2

14.4

14.6

14.8

15.0

15.2

15.4

15.6

15.8

16.0

0 10 20 30 40 50

Stea

m to

Fue

l Rat

io

Day of operation

14.65

14.68

14.96

FO EFO Same O2 setting

EFO O2 trimming

18


0

2

4

6

8

10

75 125 175 225 275

Smok

e In

dex

Fuel Flow Rate (kg/hr)

FO

FOE

with #6 FO (60X)

with FOE (60X)

19

100

120

140

160

180

200

75 125 175 225 275

NO

X (p

pm)

Fuel Flow rate (kg/hr)

FO

FOE


FO FOE FOE + Trim

% Improvement 0.2% 2.1%

Predicted -1.0% 1.0%

Smoke Index 6.0 3.0 3.5

Soot Collection 12 kg / week - 2.4 kg / week

1 Week FO firing 1 Week FOE firing

20


● The improved combustion efficiency offered by Emulsion Fuels leads to the following benefits (both in Engines and Boilers):

● Fuel economy;

● Emissions Reductions;

● Reduced Engine / Boiler maintenance.

● These benefits have been illustrated:

1. Marine power generation

2. Port Terminals

3. Industrial Boilers

PORT

21

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