When you use a forge for ironwork the atmosphere around the metal is a reducing one. The surrounding coke uses up any oxygen, protecting the metal.
In a rocket stove the air draft usually is strong and includes some excess oxygen. These conditions don't seem ideal for work with hot metal. I'm no expert though, and I bet someone could make something that works - perhaps with some limitations for the type of work you can do.
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Yeah. When I first got interested in RMHs, I looked into making an RMH-powered glass furnace.
The long and the short of it is that it would be much more effort than it's worth. To cook glass from its constituent ingredients requires a consistent temperature up around 2200 C. To simply blow glass, a temperature in the neighbourhood of 1950 C is required. *see edit below*
In addition, the burn environment would likely be so dirty that it would probably affect the quality of the glass.
How do I know this, you might wonder? My much better half is a glassblower and engraver. We have had many conversations where, thinking I have the problem licked, we suss out my ideas, and then she points out all the holes I had overlooked.
RMHs are great for burning small quantities of fuel at temperatures usually reserved for out-of-control chimney fires, and then trapping that heat for slow release.
Glass furnaces, and smelting furnaces, have different requirements, including reaching and sustaining extreme temperatures for long periods of time. Some glass furnaces are constantly up to temperature, as in the case of many shops or institutions that host many glassblowers, because not only does attaining high temperatures and cooling down again take a great deal of time, heating and cooling repeatedly is one of the chief sources of degradation in these systems.
I think that a furnace using RMH principles would no longer be an RMH, though it might have some rockety properties.
The reason natural gas or propane are typically used is because of cost, transportability, energy density, and cleanliness of combustion. Another of the benefits of using something other than wood is avoiding the kind of deforestation caused by ancient and traditional glassblowing and smelting processes.
I fully intend to use many of the heat recovery strategies found in RMHs. I think annealers, kilns, biochar retorts (that perhaps scrub the woodgas and direct it back to the combustion chamber), haybox cookers and ovens are all applications to which I could easily put the heat in the exhaust stream.
To be clear, smelting metals and cooking glass require radically different environments. Metals like copper would require a less-demanding setup, owing to a lower melting point.
EDIT: Sorry, I got some numbers wrong, owing to Celcius versus Fahrenheit conversions. This was taken from a google search:
The plants sell approximately 90 percent of the cullet to glass manufacturers, who mix it with limestone, soda ash and other raw materials. They then melt the mixture by heating it to temperatures of between 1,427 and 1,538 degrees Celsius (2,600 and 2,800 degrees Fahrenheit).
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posted 7 months ago
Yes yes. So part of the reason this is in the rs and not the rsmh section is that smelting metal ore was traditionally done in a bellowed furnace.
The mass would distribute the heat. Im thinking perhaps something that had a crucible of sorts that was within a double rams horned rocket stove that the heat would only be distributed to the ore and no mass.
Glass would perhaps need a different design as well with pehaps a chamber that was separated from the sand/lime/lye. I would need to look into more specifics to how it was traditionally done, or even how its done in modern times. I mean all i can find is that chemicals get combined and heated up and a lot of talking about nothing. And then it needs to be kept at a high temp for some amount of time to anneal.
I guess i have a problem with utilizing any material that cant be locally sourced. I dont like solar or pvc or even greenhouses or axes if i cant sustainably make the materials after they break.
I think the slump point of glass is considerably lower than the melting point around 1,251 °F, easily reached with a rocket stove.
Tacking welding separate pieces of glass together takes higher temperatures, around 1,350 °F.
So, how about a rocket that exhausts into a small insulated bell, directly onto the bottom of a stack of stainless steel steam table pans.
Each pan is filled with cullet, topped with a refractory cement cap, cast in the pan to perfectly fit the sides.
Heat the whole mess, and the weight will press the cullet together into a "sheet" of glass.
I have no opinion on glass melting/making, but blacksmithing may be achievable with a rocket stove. Control of the airflow by restricting the feed tube as is common with RMHs for optimum burning should limit the excess oxygen - the typical RMH barrel top does not degrade because it is in an oxygen-poor environment.
The main trick is getting the right part of the iron hot enough and not too hot for forging. You would need a refractory hood mostly enclosing the top of the riser. A coal forge gets such a hood by the smith's careful setup of coals, and it can be altered quickly for differently shaped workpieces. This might be a difficulty with a refractory hood, being able to adjust it to suit the immediate requirements. Or a large enough hood for most purposes might work fine without needing to be restricted for smaller workpieces - experimentation is needed.
From the above thread: "...This canner/fryer experiment started out with this dare, to see if we could beat a propane turkey fryer by boiling water in less time, using wood...In the process, we built the hottest rocket cooker either of us had ever yet experienced...After finishing the fryer cook-off, we discovered the upper part of the stove reached blacksmithing and possibly forge-welding temperatures pretty easily...I'm told it was carried away after that workshop by a master woodsman, who keeps it in his truck as a portable forge..."
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