Combustion Seminar

Wildacres 2012

1

Combustion

2

3

4

5

6

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 + 32,000 BTU or 9.6 kWh

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

7

8

9

EMISSIONS AND TESTING

10

11

12

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

PM – Particulates (particulate matter)

13

14

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

15

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

16

•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.

17

•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

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36