1. Energy Substitution of Electricity with
Natural Gas for Industrial Dryers
Kumar Aanjaneya (graduate student) & Hayden Youngs (Senior)
Completed the work
Danielle Kyser (graduated) & Karl Stimmel (graduated)
Started the work
Advisors:
Arvind Atreya (aatreya@umich.edu) & Claus Borgnakke (claus@umich.edu)
Department of Mechanical Engineering
University of Michigan, Ann Arbor 48109
1MEUS: ME 490 | 12/10/2015
2. Acknowledgements
• This work was sponsored by the DoE via the University of
Michigan Industrial Assessment Center (IAC)
• Special thanks to:
– Weiyu Cao, Yawei Chen (PhD Students), Dr. Jacek Szymczyk (Visiting
Researcher), Harald Eberhart (Glass Blower)
2MEUS: ME 490 | 12/10/2015
3. Inspiration
• Currently electric dryers are used in the plant
• Substitution with natural gas dryers, benefits:
– Cheaper to run
– Lower Carbon footprint
– Faster heating; thus increased production speed
3MEUS: ME 490 | 12/10/2015
4. Concerns
• Temperature Control
• Factory Air Quality Issues
• Flame Stability
• Incomplete Combustion
• Pollutant Formation
4MEUS: ME 490 | 12/10/2015
5. Data from the Plant
• The plant uses dryers rated at 15 kW (0.05 MMBtu/hr)
• Dryers are used for 3120 hrs/year
• Cost of Electricity: $0.08/kWh (=$23.5/MMBtu)
• Cost of Natural Gas: $5.5/MMBtu
5MEUS: ME 490 | 12/10/2015
8. Carbon Footprints
• Combustion of Natural Gas:
– 𝐶𝐻4 + 2 𝑂2 + 3.76𝑁2 → 𝐶𝑂2 + 2𝐻2 𝑂 + 7.52𝑁2
– 𝐶𝑂2 emissions per kg of Natural Gas =
𝑀 𝐶𝑂2∗1
𝑀 𝐶𝐻4∗1
=
44
16
= 2.75 kg
– Fuel rate for a 15 kW dryer =
15
𝐻𝑉
=
15
50010
x 3600 = 1.08
𝑘𝑔
ℎ𝑟
– 𝐶𝑂2 production rate for the dryer = 1.08 x 2.75 = 2.97 kg/hr
– Annual 𝐶𝑂2 production = 2.97 x 3120 = 9.2 tons/year
• Similar Energy produced by a Power plant (~40% efficient ):
– 𝐶𝑂2 production rate = 9.2/0.40 = 23 tons/year
• A reduction of 13.8 tons/year
8MEUS: ME 490 | 12/10/2015
9. Design
• Co-Annular tubes for the burner1.
• High velocity stream of air entrains high temperature combustion
products.
• Optimum mixing to achieve uniform temperatures.
9
1. Gillon, P., Chahine, M., Gilard, V., and Sarh, B. 2014. “Heat Transfer from A Laminar Jet Methane Flame in A Co-Annular Jet of
Oxygen Enriched Air” Combustion Science and Technology.
MEUS: ME 490 | 12/10/2015
10. Experimental Design
• Obstacles to induce turbulence and mixing2
• High levels of dilution to:
– Achieve complete combustion
– Achieve desired temperatures
• Burner tubes made of glass to optically determine flame color
and soot formation
• Temperature measurements at three radial locations
downstream
10
2. Guo, P., Zang, S., and Ge, B. 2010. “Predictions of Flow Field for Circular-Disk Bluff-Body Stabilized Flame Investigated by
Large Eddy Simulation and Experiments” Journal of Engineering for Gas Turbines and Power.
MEUS: ME 490 | 12/10/2015
11. Experimental Design (contd.)
• Current small-scale apparatus designed for 1kW capacity (0.016
g/s fuel inlet)
• Idea is to have low fuel momentum but high primary air flow
momentum to promote fuel-air mixing2
• Secondary (dilution) Air Flow kept constant by using a computer
fan
– For 150 C (302 F) outlet temperature, flow is ~35 CFM
11
2. Guo, P., Zang, S., and Ge, B. 2010. “Predictions of Flow Field for Circular-Disk Bluff-Body Stabilized Flame Investigated by
Large Eddy Simulation and Experiments” Journal of Engineering for Gas Turbines and Power.
MEUS: ME 490 | 12/10/2015
13. FLUENT Calculations
• FLUENT calculations were carried out for the design prior to
fabrication
• Simplifications made:
– 2D Axisymmetric model
– Neglect heat loss through walls
13MEUS: ME 490 | 12/10/2015
19. Cost savings/dryer
• Considering a 15kW dryer, running for 3120 hrs/year
• For Electricity powered dryer, annual electricity cost:
– Costelec dryer = Wel x HR x Ce=15 x 3120 x 0.08= $3,750
• For gas powered dryer, annual fuel cost:
– CostNG dryer = Wel x HR x CNG= 0.05 x 3120 x 5.5= $858
• Cost Savings = $2892/dryer
• Here:
– Wel : Power rating (kW or MMBtu/hr)
– HR: Hours of use per year (3120 hrs)
– Ce: Cost of electricity ($/kWh)
– CNG: Cost of electricity ($/MMBtu)
19MEUS: ME 490 | 12/10/2015
21. Comments
• Temperatures decreases with increase in primary air flow.
(Dilution)
• Actual temperatures are lower than predicted
– Can be explained due to heat loss in the real case
• Actual mixing higher near the wall than FLUENT
– Because of additional obstacles (spiders to hold the central tube)
• No evidence of soot on any surface
21MEUS: ME 490 | 12/10/2015
22. Comments (Contd.)
• Flame was stable.
– No flame-blowout throughout the duration of the experiments for all cases
• Calculations suggest no significant increase in humidity.
– Relative Humidity increases from 3% to 4% due to additional water in the
stream produced by combustion – air still suitable for drying
• Costs of implementation
– Burners cost around $1000-$1500 (15kW)
– Burners would require more maintenance than electrical heaters (around
$700 per year)
– With savings of $2892 per year, these costs are reasonable
22MEUS: ME 490 | 12/10/2015
23. Future Work
• Current prototype is a lab scale model
• Needs to be scaled up for usage in industry
– Use of multiple fuel jets to achieve better mixing and combustion in higher
power regimes
– Metallic burners with additional active/passive mixing enhancers
• Detailed gas analysis of exhaust
• Closer control of the flow rates
23MEUS: ME 490 | 12/10/2015
24. Future Work
• Increased control of flow to:
– Achieve desired temperatures
– Maintain flame stability (by maintaining stoichiometric ratio)
• Flame sensor and Ignitor
– Ignite the fuel at start up
– Reignite if the flame blows off or turn fuel off
24MEUS: ME 490 | 12/10/2015
