<html><head><style type='text/css'>p { margin: 0; }</style></head><body><div style='font-family: Arial; font-size: 12pt; color: #000000'><style>p { margin: 0; }</style><div style="font-family: Arial; font-size: 12pt; color: #000000"><style>p { margin: 0; }</style><div style="font-family: Arial; font-size: 12pt; color: #000000">Lists:<br>
<br>
I spent yesterday reading (skimming about half) a 200 page book
entitled: "The Mastery and Uses of Fire in Antiquity" by a J. E (Ned)
Rehder. It was much more on the combustion of char for metals working -
some but not much on production of char. I thought Mr. Rehder had
done a nice job on some aspects related to char and so tried to reach him - but I found Mr.
Rehder, who worked at the University of Toronto is recently deceased.<br>
<br>
The book is unusual in being written for an archaeological audience - but from a quite technical perspective. Among some interesting statistics are:<br>
<br>
a. He gives maximum stochiometric temperatures (called AFT for adiabatic flame temperature) for the combustion of char (1940 C, p 169) vs coke (2070 C, p 171), but shows even higher AFT values for wood if exceptionally dry. I am surprised by these numbers. <br> He drops the AFT for one type of wood by 11 degrees C for each 1% moisture and 8 degrees C for each 1% excess air. (p27)<br><br>b. He introduces a "space velocity" term that I have not seen used for our type of stoves/furnaces/kilns. He says typically 10-15 meters/minute in antiquity, now up to 40-50 meters/minute for modern apparatus that still keeps the combustibles in place. This is a measure of the power output - as zero "space velocity" gives zero power output. I don't see a way to use this in our typical stove development - but it could be very helpful in well equipped labs and when using fans/blowers.<br><br>c. He discusses the combustion of char in terms of particle diameters with emphasis on two types of combustion. In the first type (2-3 particle diameters), CO2 is produced, but then that is converted to CO (over 15 diameters - but not more) - while dropping temperature, because this is an endothermic conversion. Doesn't continue forever in deep beds because of the temperature drop. Again, something we should know - but not important in char-making stoves (which he doesn't discuss at all).<br><br>
<div style="font-family: Arial; font-size: 12pt; color: #000000">d. His appendices 2 and 3 give the equations needed to design pressure drops and air flow areas. But in his (metallurgy) business, this is mostly done in this book with "tuyeres" - air supplies that I recall seeing only in fan/blower systems. There are also (in Appendix 3) forms for natural draft. I might come back to this if I ever get back to char-making stove design - as these appendices are backed up by numerous citations (mostly anthropological). This all relates to "antiquity", but that is probably good for our simple stove and char-making. I am sure changes need to be made for TLUDs and (especially) TLODs. I hope that someone can report on any comparisons between their experimental results and anything coming out of these (or similar) theoretical treatments.<br><br>e. There are numerous places where he shows how inefficient char is in supplying heat - compared to wood. This is NOT a plug for char over wood.<br><br>f. There are some interesting computations on how much wood (and land) was needed to make carbon to process various metals (the most for copper - about 200 kg of wood for 1 kg of copper - in Chapter 13). Chapter 14 talks about deforestation due to this need for wood - and shows that is a fallacy. Deforestation has occurred - but not for making char (at least in antiquity - I think deforestation is occurring today in many African countries - becasue of the huge changes in population in many countries).<br><br>3 I found one place where the book could be obtained in electronic form for only a few bucks - but I had no difficulty getting this through inter-library loan. It is definitely of more value for anyone refining ores rather than cooking, but the book could be helpful to some on these lists.<br><br>4. If anyone else has had exposure to this book, I'd like to hear of anything else I should have caught.<br><br>Ron<br><br>Ron<br></div><br><br></div></div></div></body></html>