Interior Volume of the Kiln:
Sprung or Roman Arch:
12.5
CF = W x L x ( H Side wall + 2/3 of the arch rise)
37.5
31.5
Test kiln=?
36
Convert cubic inches to cubic feet:
Cubic inches
1728
(12 x 12 x12 = 1728)
Interior volume of the kiln:
Catenary arch :
CF = L x arch area (4/3 H x ½ base width )
Convert cubic inches to cubic feet:
Cubic inches
1728
(12 x 12 x12 = 1728)
Heat Input Calculations:
• Compare and review the following authors:
1. Lou.
2. Olsen.
3. Ward.
4. Dedell
Heat input calculations
Nils Lou -page 40
L x Ta x Pa=Q
Where:
L = Load in pounds (1500lbs- 40-60 cubic foot kiln)
Ta= Temp rise/hour in degree F (300 )
Pa= Efficiency Factor ( 80% = 1.2 )
Q = Btus Required
1500 x 300 x 1.2 =
• Assuming the kiln is insulated sufficiently
• Load includes all hard bricks, bag walls, shelves, post, etc….
• One 8lb Brick will take ?? Btus???????? Cubic foot of gas/ hour / brick
Nils Lou Page 40-41
40-60 cubic foot kiln requires 540,000 btus
Exit flue requirement:
1 sq inch of exit flue / 25,000 to 30,000 btus of input.
540,000
30,000 = 18 sq inches
so
More common is 9” x 9” flue
81sq inches
81x30,000= 2,430,000 btus!
4.5 x 5= 22.5 half brick flue ??
Olsen
Page 192
IFB kilns
natural gas:
9.1 - 6.4 cf of gas /per 1 cf of kiln
lets say
10,000 btus per cf volume
Hard brick kilns
16,000 btus per cf volume
Olsen
Page 44 -46
Sq inches or Inlet ports equal
to
Sq inches exit port ??
Burner ports
Exit ports
4.5 x 5= 22.5 x 2= 45 sq inches
9” x 5” = 45?
4.5 x 5= 22.5 x 6= 135sq inches
9x9=81sq inches?
Ward burner systems
Construciton
Cone 06 btu/h
Cone 6 btu/h
Per cubic ft -
Per cubic ft
Cone 10
Btu/h
Per cubic ft
9” hard brick
12,000-17,000
14,000-18,500
16,000-20,000
9” ifb
6,000-10,000
8,000-13,000
10,000, 16,000
6” fiber
4,000-6,000
6,000-8,000
7,000-10,000
• The lowest figure will produce firings in the 1418 hour range.
• The highest figure in each range produces a 6-7
hour firing.
Dedell
page 5 and 6
Brick Combinations
Wall construction
Wall construction
Cone 10
Cone 10
Hot face (inside)
Cold face (outside)
Cold face (outside)
Hot Face (inside)
9” HFB
--
515 degrees F
44,600 btu/hour/cu ft
4.5” HFB
4.5 K-20
285 degrees F
14,000 btu/hour/cu ft
4.5” G-26
4.5” K-20
245 degrees F
10,300 btu/hour/cu ft
9” inswool
--
185 degrees F
5,800 btu/hour/cu ft
OUR KILN:
-T.I.V. :30 CU FT
-16,000 BTU / CU FT
OUR KILN:
-T.I.V. :30T.I.V.
CU:30
FTCU FT
-16,000 BTU / CU FT
16,000 * 30 =
Energy needed- 480,000 BTU / Hour
CU FT of N.G. / Hour ??????
OUR KILN:
-T.I.V. :30T.I.V.
CU:30
FTCU FT
-16,000 BTU / CU FT
16,000 * 30 =
Energy needed- 480,000 BTU / Hour
Natural Gas = 1,000 BTU / CU FT
480,000
1,000 =
OUR KILN:
-T.I.V. :30T.I.V.
CU:30
FTCU FT
-16,000 BTU / CU FT
16,000 * 30 =
Energy needed- 480,000 BTU / Hour
Natural Gas = 1,000 BTU / CU FT
480,000
1,000 = 480 CU FT of N.G. / Hour
@ $ 1.30/ccf ( hundred cubic feet )
480 = 4.80 ccf
100
OUR KILN:
-T.I.V. :30T.I.V.
CU:30
FTCU FT
-16,000 BTU / CU FT
16,000 * 30 =
Energy needed- 480,000 BTU / Hour
Natural Gas = 1,000 BTU / CU FT
480,000
1,000 = 480 CU FT of N.G. / Hour
@ $ 1.30/ccf
4.8 * 1.30=$ 6.24/ Hour at full blast
-T.I.V. :30 CU FT
OUR KILN:
T.I.V. :30 CU FT
-16,000 BTU / CU FT
Energy needed-
16,000 * 30 =
480,000 BTU / Hour
Natural Gas = 1,000 BTU / CU FT
480,000
1,000 = 480 CU FT of N.G. / Hour
@ $ 1.30/ccf = $ 6.24/ Hour at full Blast
12 hour firing to cone 10 :
6 hours @ full
6 hours @ half
9 hours *6.24 = $56.16 / firing
480,000
2500
= 192 cu ft
Propane:
btu / cu ft
is good for
T.I.V =30 *
16,000btu / cu ft =
480,000 btu / hour
480,000
btu/gallon 92,000= 5.22 gallons / h
@ 2.00/gallon
*9hours = $ 93.96
For next week,
Clean-up your drawings:
-Ideas
-Measurements
-Etc…
Also:
-T.I.V.
-Btu’s required
-Cubic feet of gas required / hour
- cost per hours to fire
Volume to insulation ratio
Cube interior
ft
Inside volume
Area of Wall
Insulation
Volume to
Wall Insulation
ratio
1x1x1
1cf
6 sq ft
1:6
3x3x3
27cf
54 sq ft
1:2
10 x 10 x 10
1000cf
600 sq ft
1: 0.6
Olsen Chimney height (natural draft kilns)
• 3 feet of chimney for every foot of downward
pull (+) one foot of chimney for 3 feet of
horizontal pull
Bottom line- chimney height
Power burner- exhaust over any possible breathing area.
Venturi burners- depending on your gas pressure,
a rule of thumb is to double the height of
you kiln???.
Make chimney adjustable
Wood kiln- Olsen's guide will draft
Gas company
1. Give them Btu’s and cubic ft required per hour.
2. Ask what is the available gas pressure.
3. Ask size pipe is required form meter to burners ( what the
pressure drop?)
.
Find burners on Wards sheet……….. Lets say I need
600,000 btus per hour
w/ 2 power burners = 300,000 btu’s/ h for each burner.
Lets say I have - 11” wc propane
• Could I use 2 venturi burners with this pressure?
• What pressure is required to do so?
Gas flow equation
•
•
•
•
do : 11” wc and 1psi LP
Q=1326 A √H/G
Q= Discharge in cubic feet per hour
A= Area of orifice in square inches
H= Pressure in inches of water column
G= Specific Gravity of Natural Gas (NG= 0.65)
(LP = 1.50)
Alfred Steel frames:
• 9” thick brick wall construction
frame can be built congruently with
brick construction
• 4.5” brick wall with 2” 1900 board
frame and shell is built first.
• Hinged fiber doors
- Hinges are made in our machine shop
- Frame is fabricated on welding table
- Forklift is used to hold door in place while hinges are welded
to kiln frame.
Steel Fames
(Required for your drawings)
Alfred steel kiln frames are built with:
Mild Steel- 2” x 2” x 1/4” angle iron
$45/20’
3” x 3” x ¼” angle iron
$55/20’
$55/20’
4” x ¼”
flat stock
Steel prices fluctuate
We buy full pieces from I.D. Booth (Elmira NY)
Bradley Supply Hornell NY cut to length
• 2600 ceramic fiber blanket 1” thick
$.50 sq ft. box $100
8lb density- 1“thick X24“ wide X 300“ long
Inspirator burner
( Venturi / Atmospheric)
Image form: Hal Frenzel
Inspirator/natural draft
•
•
•
•
•
•
•
•
•
High gas pressure
No moving parts
Quite
Btu rating dependent on gas volume
Orifice size some what fussy
Reduction is no problem
Limited turn down ratio
Cheaper in initial cost
Relies on chimney for draft
Aspirator Burner (Forced Air)
Image form: Hal Frenzel
Aspirator/Forced air
• Low gas pressure
• Dependent on electricity
• Btu rating generally determined
by the blower
• Orifice size not that critical
• May oxidize better
• May not have wide turn down
ratio
• More versatile
• Pressurizes kiln
• No need for tall chimney
Premix
Burners
34
The Burner or
‘Flame Holder’
Shapes the Flame
35
Generic Flame Types
Combustion Chemistry
Relevant Reaction Energies and Times
(10,000 x's longer to mix then react)
Key Ideas - Energies
Chemical Potential Energy →
•
•
•
•
Initial energy of reactants
Activation energy
Final energy of products
Net change in chemical potential
energy – same as heat released
Key Ideas – Times
•
•
•
Time, Reaction Progress →
Note: Time axis is NOT to scale
Mixing time (10-2 seconds)
Ignition time (10-3 seconds)
Reaction time (10-6 seconds)
38
Flame Holder
(Burner) Functions
Shape/Direct the Flame.
Balance Mixture Speed vs. Flame Speed.
Stay Within the Flammability Limits.
May also mix fuel/oxidant.
Gas
Air
39
Nozzle Mix Burner
(generic)
4422
4423
40
In our drawings: Due Oct 7th Wed
• Cover sheet- what type of kiln, what your expectations are for
the kiln.
• Top, side, and front view of kiln
• Foundation (Blocks), Floors, Walls, Chimney and Arch
–materials/brick count and cost
• Steel frame drawing, material list and cost
• Cubic feet of interior space
• Btu’s required to heat kiln to your temp.
• Cubic feet of gas required to meet temp.
• Estimated cost/ firing
• Total cost of project -including kiln furniture ( posts and shelves)
Measuring temperature
Thermocouples
A thermocouple is a device consisting of two different
conductors (usually metal alloys) that produce a voltage
Any junction of dissimilar metals will produce an electric
potential
Type K
chromel & alumell
Type S
(+) 90% platinum 10% rhodium
(-)100% platinum
• Voltage–temperature relationship
• Cold junction compensation
• T.C. extension wire
Reading Cones
022,018,010,06, ”0” ,6,7,8,9,10
Cooler
Hotter
“0”
cooler
hotter
Combustion
79% Nitrogen 3.76 Nitrogen
Air 

21% Oxygen
1 Oxygen
Oxidation / Neutral Atmosphere for Natural Gas = 10:1
CH4 + 2O2 + (8N2) -} CO2 + 2H2O + (8N2)
Extreme Reduction Atmosphere for Natural Gas = 8:1
5CH4 + 8O2 + (32N2) -} CO2 + 4CO + 10H2O + (32N2)
Air as Oxidant
C1
H1
C1
O1 O2
H1
H2
O3
H3
H4
O4
H2 H3 H4
IGNITION
O1 O2
O3 O4
N1
N2
N3
N4
N1
N2
N3
N4
N5
N6
N7
N8
N5
N6
N7
N8
N9 N10 N11 N12
N9 N10 N11 N12
N13 N14 N15 N16
N13 N14 N15 N16
Sept. 2008 © The North
American Manufacturing
Company All rights reserved.
49
Natural Gas
Air / Fuel Ratio
& XS Air
1000 BTU / cubic ft.
Air (@ 60OF)
100 BTU / cubic ft.
If you have this volume
of natural gas to burn,
this volume of air is required to burn all the fuel (10:1ratio).
1
2
3
4
5
6
7
8
9
10:1 - Stoichiometric – Ideal - 0% excess air
50
10
Reduction firing?
• Reduction is the incomplete combustion of fuel, caused by a
shortage of oxygen, which produces carbon monoxide.
• At high temperatures, carbon monoxide gas will steal
loosely‐bonded oxygen from other materials, mainly iron and
copper.
• This changes the molecular form of the material and produces
color changes.
Extreme Reduction Atmosphere for Natural Gas = 8:1
5CH4 + 8O2 + (32N2) -} CO2 + 4CO + 10H2O + (32N2)
8 - 7: 1 -- good reduction
Reduction atmosphere
• iron give celadon glazes:
greens, blues, olive, or
grey‐green
• Small amounts of copper in
the appropriate base (Tin)
produces copper reds
• Excess copper produces
black.
Oxidation atmosphere
• iron generally produces:
-tan, brown, or rust colors
• Copper produces greens
Efficiency
1 opening
1.5” x 8’ (96”) = 144 sq.”
$tingers
$
$
$
Infiltration
Copyright  by The North American Manufacturing Company All Rights Reserved
Stacking and Furniture
Recuperators
• Your biggest heat loss is out the chimney
• Recuperators transfer heat from outgoing gas to incoming combustion air
without allowing streams to mix.
• The Streams are separated by a heat conducting wall.
• Three types are generally used: cross-flow, parallel-flow, and counter flow
Flue Gas Temp
Combustion Air Temp F.
400
600
700
700
800
7.91
8.15
900
1000
12000
13000
14000
15000
16000
8.41 12.86
8.68 13.36
9.30 14.16
9.66
10.04
800
12.41 12.48 14.53 -
% Fuel Saved
16.68
17.78
18.02
Ways to improve efficiency
-
Ways to improve efficiency
• Faster firing cycles
• No candling wet work
• Omit reduction firing
• Oxygen sensor-----10:1
• Adding a recuperatorpreheating combustion air
• Monitoring temp.
pyrometer
• Improving insulation
• Lower glaze temp
• Less thermal mass- lighter
• Lower temp clays
furniture
• Single firing
• Use alterative fuels