Download Combustion Seminar - The Masonry Heater Association (MHA

Combustion Seminar
Wildacres 2012
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Combustion
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Combustion reactions
During complete combustion, the following reactions take place:
C
+ O2
=
CO2
2H2
+ O2
=
2H2O
During incomplete combustion, we get:
2C
+ O2
=
2CO
All of these reactions are exothermic. They result in a conversion of chemical
energy into heat:
1kg C
+
2.67kg O2
=
3.67kg CO2
1kg C
+
1.33kg O2
=
2.33kg CO
+
9,500 BTU
or 2.9 kWh
1kg CO +
0.57kg O2
=
1.57kg CO2
+
9,500 BTU
or 2.9 kWh
1kg H2
8.0kg O2
=
9.0kg H2O
+ 135,000 BTU
or 40.5 kWh
+
+
32,000 BTU
or 9.6 kWh
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EMISSIONS AND TESTING
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PM – Particulates
(particulate matter)
PM2.5
•particulate matter smaller than 2.5
microns
•A blood corpuscle is 6 microns, so these
particles are in the biologically active size
range
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Soot
•Requires a flame to form
•Carbon (“lamp black”)
•Black smoke
•Very lightweight. You can have visible smoke,
yet a fairly low PM number
•Test filters are black, but have no smell
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Tar
•Requires absence of flame
(smoldering) to form
•90% of particles are smaller than 1 micron (= 0.001 mm)
•Blue smoke -- The wavelength of blue light is 0.5 microns
•Contains PAH’s – polycyclic aromatic hydrocarbons – a major health
concern, can be carcinogenic
•Measurable with a filter, but requires cooling first to condense all the tar,
by diluting with air (dilution tunnel)
•Heavy, high PM numbers
•Test filters have a very distinctive “creosote” smell. If there is no soot, the
filter can be yellow, like a cigarette filter
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•Smoldering combustion = Low burn rate = tar = creosote
•Masonry heaters are never operated at low burn rates
•Therefore, they emit little or no tar
•Any visible smoke is soot, or water (white smoke), provided you do
a top-down burn.
•If you cool the chimney on a masonry heater too much, you can get
water condensation in the chimney. However, it is impossible to get
creosote, because there is no tar in the smoke. If you see black
liquid, it is water and soot.
• It is not impossible to make tar, but you really have to try.
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•Clean burning = no visible smoke, or visible white smoke
(water)
•Even cheap non-EPA stoves can be clean if you burn them
fast enough, with unrestricted air and a firebrick firebox.
•Usually the problem is that you will overheat the house
•Heat storage is what makes a masonry heater unique
•This allows fast burn rate + low heat output
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