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Lockley

Member Since 05 Aug 2011
Offline Last Active Jul 14 2014 11:11 AM
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Posts I've Made

In Topic: At Around What Cone Can Steel Not Be Used For Kiln Components?

09 July 2014 - 01:44 PM

The technique of heat recovery from exhaust gases has a long history.  In the days of open hearth steel making they created alternating exhaust paths called "Checkers". The checkers were stacks of pyro brick that heated up on the exhaust cycle and preheated the air on the intake cycle.

 

Counter current heat exchange  is used and any number of industrial processes  to improve heating cycles.  It is also used in the feet of migrating water fowl to keep from freezing in ice filled ponds. :)

 

In my own experience I have used Black Iron pipe ( not galvanized pipe) with propane in a blower system to increase the temperature I achieve.   Black iron is relatively inexpensive compared to stainless steel, and because it is thread-able by most suppliers it can be assembled  in manifolds without welding.  This makes replacement of parts a days work not a weeks.  I used straight pipes not coiled, and of a large diameter to slow the flow down with out reducing volume.  I didn't worry about the iron pipes because it is kind of like the "Mr. Wizard" trick of boiling water in a paper cup over an open flame. As long as air flowed through the pipe was ok despite the temperature would have melted steel.

 

For a wood fired system I have been toying with designs using two different  sizes of  fire place  flue tiles.  One outer and one inner.

 

 

 

 

 


In Topic: Real-Time Kiln Advice (Kiln Curently Firing)

06 June 2014 - 09:33 AM

Have you considered the option of two supply cylinders with two regulators supplying one line  with a control valve leading to your burner?

Set the regulators to a slightly higher pressure than needed  and use the valve to throttle delivery down to your requirements.

 

Just a thought

Lockley


In Topic: Noob Seeks Advice Building Kiln On The Cheap

06 June 2014 - 09:07 AM

A couple of thoughts on your project. 

one) Small propane furnaces / kilns are the least efficient way to fire  any thing.  For the temperature achieved the total BTU expense is inversely proportional to the volume heated per item.  As a means of experimenting with the local clay I rather doubt you will find it satisfactory.  Since you are a rural area you might find it better to experiment with wood/agricultural waste fired kilns.  I would not dismiss the local potters so casually.  In my experience with various crafts local knowledge will often trump academic knowledge. Making friends with local potters may teach you things about local conditions and materials that will speed you toward satisfactory results.

In addition my experience with small propane fired furnaces/kilns/forges, has shown that control problems increase as size decreases.

 

two) Commercial burners from companies like WARD Burners are by far the most practical way to build  a kiln. Failing that there is a resource for building burners that I have not seen listed here before.

 

Gas Burners for Forges, Furnaces & Kilns

 

by Michael Porter   copy right 2004

 

Published by SkipJack Press, Ocean Pines, MD  Library of Congress # 2003115257

 

The contents of this book will short cut a lot of errors and futile effort,  I wish it had been available 30 years ago.

It is possible to build a Kiln burner with very simple plumbing fixtures but making one with the necessary range of turn down (variation of BTU output ) is difficult and very difficult with out first class gas regulators.

 

You may want to read the extensive discussion of Kiln firing that appeared on this forum last week. 

Good Luck

Lockley

 


In Topic: Real-Time Kiln Advice (Kiln Curently Firing)

30 May 2014 - 09:18 AM

Wow, John Baymore  has provided a world of detailed information and analysis of this problem.  Wish,  I could make it to New Hampshire and sit at his feet.

 

I'd like to and something about regulators.  If you have not already, go to your local industrial gas, welding gas suppler, and purchase a high volume propane regulator.  They are relatively expensive but provide the capacity and volume needed in this application.  Propane fuel is used in an number of industrial application so they are usually available quickly on order.    There are, in most manufacturer catalogues, three size of each regulator bodies. You want the largest.   I like the suggestion of ganging together several 100# tanks.   However, If you decide to do that consult your supplier of welding supplies and purchase the equipment they supply to industry for assembling a Propane Supply manifold. 

You may not realize it but, even though you may see your self as a craftsman artist,  when you shift to firing in an independent  kiln your feet are on the first rung of the industrial ladder. Many aspects of Ceramics are best done by creative and  envelop stretching artists but running a kiln is a serious business and no place for cheaping  out.

 

Lockley


In Topic: Real-Time Kiln Advice (Kiln Curently Firing)

23 May 2014 - 09:17 AM

I think your problems with this kiln would indeed be solved with a power burner.  Naturally aspirated systems are a little tricky to operate in my experience.  In my checkered career I've built a large number of naturally aspirated systems.  I've found low pressure systems to be the most difficult to make work.  Naturally aspirated burners are incredibly sensitive to down stream and up stream resistance . Too much resistance in front of the burner and it will back burn.  To much resistance behind the burner it burn orange and smoky.  There is another problem, which is referred to  as resistance to mass transfer, meaning that hot gases are harder to move in volume because the individual molecules are moving so fast in a chaotic pattern.

 

The burn problem you show in your video tells me that the total velocity  of your air fuel mixture is to slow for the diameter of the burner.   How to solve it? Either reduce the resistance in front of it or increase the gas velocity entraining air by increasing pressure.  Given your previous discussion I vote for moving your splash bricks toward the center and moving your whole bag wall back an inch or so.

 

Lockley