Evaluation of a Wood Pellet Burner in a Bulk Tobacco Curing Barn

R. Taylor Brown and T. David Reed Virginia Tech

Southern Piedmont Center

2018

_TW

C72

_Ree

d.pd

fT

WC

2018

(48)

- D

ocum

ent n

ot p

eer-

revi

ewed

Flue-Cured Tobacco

Curing is an energy intensive process requiring fuel for heating the barn and electricity for ventilation

Curing is a substantial production expenseCuring contributes significantly to the

environmental footprint of tobacco production

2018

_TW

C72

_Ree

d.pd

fT

WC

2018

(48)

- D

ocum

ent n

ot p

eer-

revi

ewed

Flue-Cured Tobacco Barns 2018

_TW

C72

_Ree

d.pd

fT

WC

2018

(48)

- D

ocum

ent n

ot p

eer-

revi

ewed

Energy Usage Associated with the Curing of Flue-Cured Tobacco

Propane is the most common curing fuel Natural gas usage is increasing where available Fuel oil use is relatively minor Grower have become more aware of curing efficiency

and have taken steps to reduce fuel consumptiono Curing with a wet bulb

o Automatic curing controls

o Barn insulations

o Energy audits to quantify energy usage and identify potential energy conservation options

o Higher efficiency curing barns, heat exchangers, and burner

2018

_TW

C72

_Ree

d.pd

fT

WC

2018

(48)

- D

ocum

ent n

ot p

eer-

revi

ewed

CO2 Resulting from Curing Tobacco

Typical range of curing efficiency is 8 to 11 lbs. of tobacco per gal. of propane

12.6 lbs. of CO2 produced per gal. of propane

Assuming 3500 lbs. of tobacco per curePropane consumption = 318 to 437 gal. per cure

Corresponding CO2 emissions would be4,006 to 5,506 lbs. per cure

or1.14 to 1.57 lbs. of CO2 per lb. of cured tobacco

2018

_TW

C72

_Ree

d.pd

fT

WC

2018

(48)

- D

ocum

ent n

ot p

eer-

revi

ewed

CO2 Emissions

The use of renewable, biomass fuels such a wood would substantially reduce CO2 emissions. The use of renewable fuels is limited in the U.S.

for various reasons.

2018

_TW

C72

_Ree

d.pd

fT

WC

2018

(48)

- D

ocum

ent n

ot p

eer-

revi

ewed

Project Objectives

1. Evaluate the first time use of a wood pellet burner with an air-to-air heat exchanger in a bulk tobacco curing barn.

2. Consider the on-farm production of biomass pellets as an alternative to premium grade wood pellets.

2018

_TW

C72

_Ree

d.pd

fT

WC

2018

(48)

- D

ocum

ent n

ot p

eer-

revi

ewed

Why consider a wood pellet burner rather than wood-fired hot water boiler system ?

• Incremental adoption• Readily available, convenient fuel

2018

_TW

C72

_Ree

d.pd

fT

WC

2018

(48)

- D

ocum

ent n

ot p

eer-

revi

ewed

Materials and Methods A Kendel PB-680 wood

pellet burner was installed with a custom made air-to-air heat exchanger in a Tytun Elite 3-box test tobacco curing barn.

Comparisons were made to a similar 3-box Tytun barn with a high efficiency heat exchanger and propane burner.

2018

_TW

C72

_Ree

d.pd

fT

WC

2018

(48)

- D

ocum

ent n

ot p

eer-

revi

ewed

2018

_TW

C72

_Ree

d.pd

fT

WC

2018

(48)

- D

ocum

ent n

ot p

eer-

revi

ewed

2018

_TW

C72

_Ree

d.pd

fT

WC

2018

(48)

- D

ocum

ent n

ot p

eer-

revi

ewed

2018

_TW

C72

_Ree

d.pd

fT

WC

2018

(48)

- D

ocum

ent n

ot p

eer-

revi

ewed

Hourly Pellet Consumption vs. Temperature Throughout Cure

2018

_TW

C72

_Ree

d.pd

fT

WC

2018

(48)

- D

ocum

ent n

ot p

eer-

revi

ewed

Wood Pellet Burner Evaluation

Cure no.1 2 3 4

Woo

d pe

llets

(lbs

/ cu

re)

600

700

800

900

1000

1100

1200

20162017

2018

_TW

C72

_Ree

d.pd

fT

WC

2018

(48)

- D

ocum

ent n

ot p

eer-

revi

ewed

Wood Pellet Burner Evaluation

Cure no.1 2 3 4

Woo

d pe

llets

(lbs

) per

pou

nd o

f tob

acco

0.0

0.5

1.0

1.5

2.0

20162017

2018

_TW

C72

_Ree

d.pd

fT

WC

2018

(48)

- D

ocum

ent n

ot p

eer-

revi

ewed

Wood Pellet Burner Evaluation

Cure no.1 2 3 4

Ener

gy c

onsu

mpt

ion

(Btu

/ lb

)

4000

6000

8000

10000

12000

14000

Wood pellets 2016Wood pellets 2017

2018

_TW

C72

_Ree

d.pd

fT

WC

2018

(48)

- D

ocum

ent n

ot p

eer-

revi

ewed

Wood Pellet Burner Evaluation

Cure no.1 2 3 4

Ener

gy c

onsu

mpt

ion

(Btu

/ lb

)

4000

6000

8000

10000

12000

14000

Wood pellets 2016Wood pellets 2017Propane 2016 Propane 2017

2018

_TW

C72

_Ree

d.pd

fT

WC

2018

(48)

- D

ocum

ent n

ot p

eer-

revi

ewed

2018

_TW

C72

_Ree

d.pd

fT

WC

2018

(48)

- D

ocum

ent n

ot p

eer-

revi

ewed

2018

_TW

C72

_Ree

d.pd

fT

WC

2018

(48)

- D

ocum

ent n

ot p

eer-

revi

ewed

2018

_TW

C72

_Ree

d.pd

fT

WC

2018

(48)

- D

ocum

ent n

ot p

eer-

revi

ewed

Curing Cost Comparison

Curing Cost (cents per lb)

Wood Pellets Propane P-value

2016 10.8 9.6 0.1324

2017 11.6 9.0 0.0457

Combined 11.2 9.3 0.0008

Fuel prices: Premium wood pellets =$200 per ton and LPG = $1.20 per gal.

2018

_TW

C72

_Ree

d.pd

fT

WC

2018

(48)

- D

ocum

ent n

ot p

eer-

revi

ewed

CO2 Emissions

90 percent reduction in CO2 emissions

Wood pellets =0.098 lbs CO2 per lb tobacco

Propane = 0.983 lbs CO2 per lb tobacco

2018

_TW

C72

_Ree

d.pd

fT

WC

2018

(48)

- D

ocum

ent n

ot p

eer-

revi

ewed

Conclusions• The high efficiency wood pellet burner was an

effective alternative to propane.

• Curing with wood pellets required additional Btu’s compared to the high efficiency propane burner.– Ash accumulation in heat exchanger

• Cost of curing was marginally higher

• Use of wood pellet fuel substantially reduced CO2 emissions associated with tobacco curing

2018

_TW

C72

_Ree

d.pd

fT

WC

2018

(48)

- D

ocum

ent n

ot p

eer-

revi

ewed

Acknowledgements

Altria Client ServicesJapan Tobacco International

Philip Morris International

2018

_TW

C72

_Ree

d.pd

fT

WC

2018

(48)

- D

ocum

ent n

ot p

eer-

revi

ewed

Pellet Comparison

Heating value(Btu)

Inorganic ash(%)

Chloride(ppm)

Premium wood pellet standard > 8000 <= 1 <= 300

On-farm annual grass biomass 7100 - 7500 6.2 – 9.1 1800 –

3400

2018

_TW

C72

_Ree

d.pd

fT

WC

2018

(48)

- D

ocum

ent n

ot p

eer-

revi

ewed