1

Kitchen Grease Filtration

Some information from “The Facts About Mechanical Grease Filters”, published in the ASHRAE Journal. Authors Andrey Livchak, Derek Schrock (Halton Company), Matti Lehtimaki, Aimo Taipale (VTT, Finland)

Derek Schrock, Halton Company Email: dschrock@haltoncompany.com Web: www.haltoncompany.com

Presented to the National Air Filtration Association September 24, 2005

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The Myth n Many manufacturers claim

the mechanical filter efficiency to be 90% or higher.

n Does it mean that these filters remove 90% of grease from kitchen exhaust?

n Then why we are still cleaning the exhaust ducts and why is there grease on the roofs?

4

Emissions from cooking process

0

10

20

30

40

50

60

Gas

Grid

dle

Ele

ctric

Grid

dle

Gas

Fry

er

Ele

ctric

Frye

r

Gas

Bro

iler

Ham

burg

er

Ele

ctric

Bro

iler

Ham

burg

er

Gas

Bro

iler

Chi

cken

Ele

ctric

Bro

iler

Chi

cken

Gas

Ove

n

Ele

ctric

Ove

n

Cooking Operation

Tota

l Gre

ase

Emis

sion

s (lb

./100

0 lb

.) Total Emissions (lb./1000 lb. product)

ASHRAE RP-745

Data from ASHRAE Project 745-RP: Identification and Characterization of Effluents from Various Cooking Appliances and Processes as Related to Optimum Design of Kitchen Ventilation Systems

5

0102030405060708090

100

Gas

Grid

dle

Ele

ctric

Grid

dle

Gas

Fry

er

Ele

ctric

Frye

r

Gas

Bro

iler

Ham

burg

er

Ele

ctric

Bro

iler

Ham

burg

er

Gas

Bro

iler

Chi

cken

Ele

ctric

Bro

iler

Chi

cken

Gas

Ove

n

Ele

ctric

Ove

n

Cooking Operation

% G

reas

e C

ompo

sitio

n

% Particulate % Vapor

Particulate and Vapor Breakdown

ASHRAE RP-745

Data from ASHRAE Project 745-RP: Identification and Characterization of Effluents from Various Cooking Appliances and Processes as Related to Optimum Design of Kitchen Ventilation Systems

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Emissions by Particle Size (0.3 to 10 μm)

0.000

0.100

0.200

0.300

0.400

0.500

0.600

0.700

0.800

0.900

1.000

0.35 0.47 0.62 0.84 1.14 1.44 1.88 2.57 3.46 4.69 6.20 8.37

Mean Particle Diameter, microns

Mas

s (lb

./100

0 lb

. foo

d co

oked

)

Gas Griddle Gas Broiler, hamburger Electric Broiler, hamburger Gas Broiler, chicken

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Grease Filter Standards

n UL 1046 Grease filters for exhaust ducts n ULC–S649-93 Standard for grease filters for

commercial and institutional kitchen exhaust systems

n ULC 710 Standard for grease extractors for exhaust ducts

n Navy NBSIR 74-505 Test of grease interception n VDI 2052, Part 1 Ventilation equipment for

kitchens. Determination of capture efficiency of aerosol separators in kitchen exhaust

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0

10

20

30

40

50

60

70

80

90

100

1 2 3 4 5 6 7 8 9 10

particle size, micron

Effic

ienc

y, %

Cyclonic Filter Baffle I Baffle II

Filter Efficiency @ 140 cfm/ft

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0

10

20

30

40

50

60

70

80

90

100

1 2 3 4 5 6 7 8 9 10

particle size, micron

Effic

ienc

y, %

Cyclonic Filter Baffle I Baffle II

Filter Efficiency @ 200 cfm/ft

10

0

10

20

30

40

50

60

70

80

90

100

1 2 3 4 5 6 7 8 9 10particle size, micron

Effic

ienc

y, %

Cyclonic Filter Baffle I Baffle II

Filter Efficiency @ 270 cfm/ft

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Filter efficiency as function of the airflow (cyclonic filter)

0

10

20

30

40

50

60

70

80

90

100

1 2 3 4 5 6 7 8 9 10

particle size, micron

Effic

ienc

y, %

140 cfm/ft 200 cfm/ft 270 cfm/ft

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Filter efficiency as a function of cooking process

1. Determine emissions for a cooking process (vapor and particulate) including particle distribution for particulate emissions.

2. Determine filter efficiency as function of particle size and air flow range through the filter.

3. Calculate filter efficiency for the cooking process by overlaying the filter efficiency curve with the particle distribution curve for the cooking process at the design airflow through the filter.

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Filter efficiency as a function of cooking process

0% 10% 20% 30% 40% 50% 60% 70%

Filter A Filter B Filter C

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Filter efficiency as a function of cooking process – particulate only

0% 10% 20% 30% 40% 50% 60% 70% 80% 90%

100%

Filter A Filter B Filter C

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New Standard

n ASTM F2519-05: Standard Test Method for Grease Particle Capture Efficiency of Commercial Kitchen Filters and Extractors

n Incorporates parts of ASHRAE Standard 52.2 and the VDI 2052 Standard.

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Particulate Selection

n Instead of polydisperse solid-phase (dry) potassium chloride (KCl) particles, oleic acid particles are generated since they represent the main fat in cooking oils and hamburger fat and are “sticky”.

n Currently only tests particle removal efficiency: n Work will continue to add a vapor efficiency

component.

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System Setup n Can utilize

either a vertical or horizontal duct arrangement

n Needed to simulate an actual cooking environment

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Particulate Size Ranges Bin Mean Particle

Size (μm)

1 0.35

2 0.47

3 0.62

4 0.94

5 1.14

6 1.44

7 1.88

8 2.57

9 3.46

10 4.69

11 6.20

12 8.37

These match the particle ranges specified in ASHRAE Standard 52.2: Method of Testing General Ventilation Air-Cleaning Devices for Removal Efficiency by Particle Size

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Test Procedure

1. Take background samples 2. Take samples with filter installed

Or install a “fixed extractor” hood 3. Take samples without filter installed

Or install a “reference hood” 4. Repeat steps 2 and 3 several times 5. Ensure sample penetration and

consistency are in order

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Efficiency Calculation

n The particulate capture efficiency for any particle size is calculated as:

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UV Light Technology

n UVC lights placed in the exhaust plenum of kitchen hoods. n The UV light breaks the longer chains of

grease molecules. n Ozone oxidizes the smaller particulate matter

and vapor components. n Most effective on smaller particulate and

vapor n Efficient filtration still needed prior to the UV lights.

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UV Light Can…

n Minimize the buildup of grease in ductwork leading to: n Reduced frequency of cleaning n Increased fire protection safety

n Eliminates grease buildup on roofs and enhances the life of exhaust fans.

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Conclusions

n The efficiency of grease removal devices varies with the filter design.

n Efficiency of the mechanical grease filters is a function of filter design, cooking operation and airflow (pressure drop) across the filter.

n The theoretical maximum grease removal efficiency (as a % of vapor and particulate cooking emissions) ranges from 5 to 70%.

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Conclusions continued

n ASTM has adopted a grease filter efficiency standard: F2519-05.

n New technologies, such as UV light, can provide enhanced grease abatement.