Comparing Wood Pellets for Heat Output and Burn Time

Researchers Picture

Researched by Brandon R.
2005-06




PURPOSE


The first purpose of this experiment was to find which brand of wood pellets would burn the longest.

My second purpose was to find which brand of wood pellets would burn the hottest.

I became interested in this idea after we bought our wood pellet stove. All of my parents’ friends told us of many different brands of wood pellets that burned the longest and the hottest.

The information gained from this experiment could help consumers who own a wood pellet stove know which brand of wood pellets burn the longest and hottest. 


HYPOTHESIS


My first hypothesis was that Bear Mountain Pellets would burn the longest.

My second hypothesis was that Lignetics Wood Pellets would burn the hottest.  

I based my first hypothesis on my own experience using Bear Mountain Pellets. I had found that 18.1 kg burned for 36 hours.

 I based my second hypothesis on the fact that the Lignetics Wood Pellets cost the most. Sometimes you get what you pay for.

EXPERIMENT DESIGN

The constants in this study were:
•    The same level of burning (high)
•    The same beginning temperature
•    The same Pellet Stove (Pioneer Bay Pellet Insert)
•    The same beginning weight of the wood pellets (2.5 kg)
•    The same placement of the thermometer (middle of grill)
•    The same number of trails (3)   

The manipulated variables were different brand of wood pellets inserted into the pellet stove.

The responding variable was the time it took the pellet stove to burn 2.5 kg of wood pellets. Also the average temperature of the pellet stove. 

To measure the responding variables I timed in minutes how long it took the wood pellet stove to burn the different brands of wood pellets. Also I measured the average temperature of the wood pellet stove in degrees Celsius using an over thermometer.

MATERIALS

QUANTITY            ITEM DESCRIPTION
       1                        18.1 kg bag of Bear Mountain Pellets
       1                        18.1 kg bag of Lignetics Wood Pellets
       1                        18.1 kg bag of N. Idaho Energy Logs Inc Wood Pellets
       1                        18.1 kg bag of Hot Shots Wood Pellet Fuel
       1                        Pioneer Bay Wood Pellet Stove
       1                        Oven Thermometer
       1                        Stop Watch
       1                        Recording Sheet (Table)
       1                        Triple Beam Balance 

PROCEDURES

1.      Clean the wood pellet stove removing all pellets and make sure that it is cooled down.
2.      Place 2.5 kg of Bear Mountain Pellets into the stove.
3.      Place the thermometer on the grill so that it is in the middle.
4.      Turn the pellet stove on high and start the timer.
5.      Every 20 minutes record the temperature on the thermometer.
6.      After the pellets have burned completely record the time.
7.      Now record the maximum temperature.
8.      Repeat steps 2-7 two more times with the same brand of wood pellets.
9.      Repeated steps 2-8 but change the brand of wood pellets to Lignetics.
10.    Repeated steps 2-8 but change the brand of wood pellets to North Idaho Energy Log Inc.
11.    Repeated steps 2-8 but change the brand of wood pellets to Hot Shots
12.    Find the average time and temperature for each brand.

RESULTS

The original first purpose of this experiment was to find which brand of wood pellets would burn the longest.

My original second purpose was to find which brand of wood pellets would burn the hottest.

The results of the experiment were that North Idaho Energy Logs Incorporated wood pellets had the longest burning time of 111 minutes. Hot Shots wood pellets had the second longest burning time of 107 minutes then Bear Mountain with 100 minutes., and Lingnetics with 96 minutes. Bear Mountain had the maximum temperature of 150°C. then Lingnetics with 138°C., then Hot Shots with 123°C, then N. I. E. L. Inc with 120°C. After reading over the data the best overall wood pellet brand would be Bear Mountain and North Idaho Energy Logs Inc.   

See the table and graph below.

CONCLUSION

My first hypothesis was that Bear Mountain Pellets would burn the longest.

The results indicate that my first hypothesis should be rejected, because Bear Mountain wood pellets were third. First was N. I. E. L. Inc. with 111 min. and second was Hot Shots with 107 min.

My second hypothesis was that Lignetics Wood Pellets would burn the hottest.  

The results indicate that my second hypothesis should be rejected, because Lingnetics wood pellets did not burn the hottest. Bear Mountain did.

After thinking about the results of this experiment, I wonder if the type of wood pellet stove would affect the outcome.

If I were to conduct this project again I would conduct more trials. I would also use a larger amount of wood pellets per test. I’d use a more exact temperature measurement, such as a computerized thermo-couple.


RESEARCH REPORT

Introduction

Humans must maintain a reasonably constant body temperature, approximately 98.6° F. or 37° C.  During the winter in areas far from the equator, it is hard for humans to maintain their body temperature without artificial heat. Most homes today are heated to help maintain a constant temperature and to provide comfort.  It has become more popular for people to accomplish this by burning wood pellets, which are more natural compared to using electric or gas heaters. Wood is a renewable resource and pellet fuel is actually made from discarded sawdust and chips. Pellet fuel is a form of recycling. Wood pellets may be the fuel of the future!   

Wood Pellets

Wood Pellets are small compacted pieces of sawdust. The manufacturing of wood pellets begins when a truckload of raw material, such as wet and dry sawdust chips, are delivered to a plant. The raw material is then dumped into large piles. Large machinery loads the material into an in-feed system, which then meters it into a screener, which separates the chips and the sawdust. The chips are placed into a pre-grinder and then mixed with the sawdust. The material is placed in a silo that will be metered into a dryer. The sawdust is now placed into cyclones, which blow air that will remove the water vapor. The sawdust is then moved into another screener, which separates the fine sawdust from the coarse. The coarse sawdust enters a hammer mill and is reduced in size. The material is then mixed and placed in a mill where the pellets are formed. The sawdust is moistened with steam and then rolled in a pellet machine and extruded through a hole with dye. The wood pellets are now cooled and stored for packing and shipping.  

Wood Pellet Stoves

Wood pellet stoves are used mainly to heat homes. The basic operation of a wood pellet stove starts with wood pellets being placed into a hopper. The bottom of the hopper is an auger run by a motor. The pellets are then moved into a firepot. In the back of the firepot there is an igniter that lights the wood pellets. The room’s air is drawn into the stove then blown across a heat exchanger, which heats it to at about 120ºC. The hot air is then blown back into the room. After a few pellets are burned ash is made. It then falls into an ash trap that has to be emptied from once a week or two times a year.
     
Fire Triangle

The fire triangle is a concept that explains three elements that are required for combustion to occur. Fuel or any combustible material is the first required element. The second element is ignition or a heat source. The heat vaporizes the fuel and when it reaches its ignition temperature it burns. Third is oxygen in adequate quantities. If one of these elements is not present combustion will not occur.
 

Fire/Combustion

Fire is mainly used in homes today to heat living spaces, heat water, or to cook with. Combustion is made up of 4 things: Fuel, Oxygen, Ignition and then Chain Reaction. There are also 4 different types of combustion:  Rapid, Slower, Complete, and Incomplete Combustion. 

Rapid combustion is when the combustion has a large amount of heat and light energy. Rapid combustion is used in machinery such as internal combustion engines.

Slow combustion is when combustion takes place at low temperatures. Respiration is an example of slower combustion.

Complete combustion occurs when oxygen is plentiful during burning. This produces a small amount of by products. This is where some elements yield to most common oxides. This is almost impossible to complete unless is in a controlled area.

Incomplete combustion occurs when there is too little oxygen for complete combustion to occur. Some fuel will burn but will produce many products.

                                               Fuel and Oxygen                                                    

Today’s main fuels for fireplaces are wood, wood pellets, and natural gas. When a wood log, for example, is burning it releases gases, which are created from the hot decomposing wood. Then oxygen from the air is mixed with the created gases. The wood is now ignited. Now the flame decomposes more of the wood on the log. More gases are created. This process is self-supporting.   

Ignition

A fire can start when fuel becomes hot enough to release flammable gases so combustion can occur. At that temperature, which is called the fuel’s piloted ignition temperature; a flame or spark will start the combustion. Electricity can also create the igniting spark.

Larger pieces of wood require a lot of heat before they can ignite, but a small piece of wood, such as a wood pellet, needs less heat to ignite.      

Chain Reaction

Finally fire needs a chain reaction to keep burning. The heat from the fire’s flame drives the chain reaction. When a wood log, for example, is ignited, which is about 260°C, the wood starts to decompose. This creates gases and char. The compositions of the gases are represented as the compound CH2O. CH2O combines with oxygen (O2) that is in the air. Also water Vapor (H2O). The chain reaction in wood burning is shown below.



6 C10H15O7   +   heat   →   10 CH2O   +   C50H10O
 Wood                     Volatile Gases     Char
_______________________________________________________
CH2O   +   Air   →   CO2   +   H2O   +   CO   +   C   +   9 N2
     Volatile Gases             Carbon      Water     Carbon      Carbon     Nitrogen
                                    Dioxide                 Monoxide 


Summary

Fire is a popular heating source. It is probably better than running a gas or electric heater. Wood or wood pellets are the most natural way to heat or fuel fire. Wood pellets are cost-effective way to fuel fireplaces (Wood pellet stoves). This year due to high gas prices wood pellet stoves are selling at an all time high.
 
BIBLIOGRAPHY

Allaby, Michael Fire. New York, NY: 1993. pp. 90, 104.

Cedars-Sinal. “Fire Triangle.” January 14, 2006 <http://www.csmc.edu/6666.html>

“Combustion.” January 14, 2006 <http://en.wikipedia.org/wiki/combustion>

Danson. “How we make our wood pellets” January 27, 2006 <http://www.dansons.com/what-are-wood-pellets.htm>

Darling, David “Pellet Stove” December 29, 2005 <http://www.daviddarling.info/encylopedia/r/aepellet-stove.httm

“How Combustion Occurs.” Microsoft Encarta. 2005

New England Wood Pellets Inc. “How We Make Wood Pellets.” December 26, 2005 <http://pelletheat.com/pellets/process>

New England Wood Pellets Inc. “How We Make Wood Pellets.” December 26, 2005 <http://pelletheat.com/pellets/process_1-16.#photo>

Quintiere, James G. “Fire.” January 5, 2006 <http://www.worldbookonline.com/wb/article?id=arl97340>

Tumpike, Sherman. Oxygen. Connecticut: Danbury 1996 pp. 34-35



ACKNOWLEDGEMENTS

I would like to thank the following people for helping make my project possible:
  • My mom and dad for supporting me and paying for the materials needed to conduct my project.
  • My Grandma and Grandpa for the oven thermometer.
  • Mr. Newkirk for his support, guidance, and time while designing and doing my science project.
  • Mrs. Viernes for her help and support, also for helping me with my research report.   


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