Can a Candle Flame be Improved for Better Efficiency?

[Majorana]

TL;DR Summary

Is it possible to improve the flame produced by an ordinary candle? To reduce soot and raise the temperature?

Good day to everybody,

I'm wondering whether it could be possible to improve the quality and efficiency of an ordinary (wax/paraffin) candle flame.
These flames are relatively cold, and give off a substantial amount of soot (i.e. unused fuel).
I wish to raise the temperature of the combustion products in order to increase the quantity of thermal energy released by the candle.

I don't know whether it's possible to steer a candle flame from reducing (yellow) to oxidizing (blue).

I've heard of "simmer rings" - used with alcohol burners, not with candles - that produce a beautiful blue, hot flame (see attached picture).
I could not find the details of these rings, I don't know whether they can be built and work successfully when coupled to a candle.
There are widely diffused miniature butane torches, based on an inexpensive cigarette lighter, that produce an extremely hot, blue flame instead of the usual yellow flame of the lighter: but it works only because the butane in the lighter is under pressure so it can be used to draw in a substantial amount of air, producing a nice oxidizing flame. Nothing like the wax in a candle.

...Any idea about how to do the trick?...

 

[jedishrfu]

I don't think there is such a device for a candle. I've seen candle caps/toppers on church candles but I think those just preserve the candle from burning too fast and too unevenly.

http://thecandlereview.com/blog/the-importance-of-candle-toppers/

 

[DaveC426913]

I'm wondering whether it could be possible to improve the quality and efficiency of an ordinary (wax/paraffin) candle flame.

These flames are relatively cold, and give off a substantial amount of soot (i.e. unused fuel).

It's an interesting idea, but what problem is this solution proposing to solve?

Why do consumers buy candles? They buy them for many reasons, but a primary one is the soft warm light they give off. That aesthetic quality is not an undesirable side effect; it is the goal. To my eye, what you're proposing seems antithetical to a candle's primary purpose.

If one wants a hot, efficient, dim blue flame, it's not because one is planning to use it as a candle.
If one wants a hot, efficient, dim blue flame, one makes a more appropriate choice of fuel.

And if one wants a clean-burning efficient fuel for lighting needs, one gets a Coleman kerosene lantern.

Yes?Side note: as a sailor, I am often warned of the dangers of a hot dim, blue flame that is the hallmark of alcohol stoves: the flame is practically invisible in some circumstances, and therefore presents a heightened danger for fires in circumstances such as the enclosed space of a boat. But the caution is just as valid in unsupervised household environments where kids, pets and drunk guests frolic. In such an environment, you want a cool and highly visible flame.

 

[Baluncore]

In such an environment, you want a cool and highly visible flame.

And that is why you should add 1% acetone to ethanol fuel.
The flame is then yellow and visible in sunlight.

 

[jedishrfu]

Sometimes candle buying and gifting are a lot like the fruitcake gift during Xmas. The recipient doesn't know what to do with it and so gifts it to someone else the following year.

 

[Majorana]

@DaveC426913 you are absolutely correct. I do not need to use the candle (tealight, to be more precise) as a source of light. I need to use tealights for coocking purposes.
In my country, the price of both natural gas and LPG is skyrocketing under the official pretext of the war (actually, it's just financial speculation, as with many other primary goods). Prices are increasing almost by the hour. Most people are facing the choice between paying the gas bill or purchase the food to cook, but not both. Luckily, I discovered a niche source of 4-hour tealights (1", the narrowest size) where we can still purchase these little candles at a price that is very competitive compared with present gas prices (that are bound to increase even more in the next months). We don't know how long that source will last until they decide to "adjust" the prices: for that reason we are stockpiling 4-hour tealights like mad.
I am doing cooking trials with the 1" tealights arranged in a tight pattern, and it works like on the small burner of a gas range. That is the problem: like the SMALL gas burner. I can cook foods that don't require a strong flame, but that reduces too much the range of foods that can be cooked with this technique. Since the range of available foods is bound to shrink drastically in the near future, we need to be able to cook any food we will be able to find. The matrix of tealights lacks the "punch" because the heat released by a tealight (or any common paraffin candle) is lower than the heat it could release if the combustion were more efficient.
I must find a way to steer the flame towards "oxidizing", i.e. reduce the lost fuel (soot) and increase the heat released.

 

[DaveC426913]

Ah I see.

I suspect your best bet might be to melt the paraffin first and decant it into a device that draws up the paraffin and maximizes its exposure to air before burning it. (like a bunsen burner, but for liquid fuel)

 

[nettleton]

Instead of burning in air increase the oxygen concentration reducing the soot level and increasing the temperature of the flame.

 

[anorlunda]

Ah I see.

I suspect your best bet might be to melt the paraffin first and decant it into a device that draws up the paraffin and maximizes its exposure to air before burning it. (like a bunsen burner, but for liquid fuel)

I think @DaveC426913 is on the right track.

You may (or may not) succeed in adapting a Primus Stove to use pressurized, melted paraffin from a candle as an alternative to kerosene fuel. You would need a second stove (or other candles) to keep the fuel tank hot. The chances of making that work may be small, but an experimental trial would not be expensive.

https://en.wikipedia.org/wiki/Primus_stove

Have you looked for affordable sources of ethanol in your country?

 

[DaveC426913]

Instead of burning in air increase the oxygen concentration reducing the soot level and increasing the temperature of the flame.

Yeah but that's a prohibitively expensive solution because you need to provide the oxygen. See OP's post #6 for context.

Better to use a cheap, passive system to mix the air in with the fuel.

 

[DaveC426913]

You would need a second stove (or other candles) to keep the fuel tank hot.

Or some sort of passive single-stage heat shunt system.

Divert a small portion of the heat back to keeping the fuel warm.

That's how they do it in the shuttle rocket engines! The liquid fuel is passed through lines surrounding the exit nozzle to warm the fuel up to temp before squirting it into the chamber.

You'd want to minimize loss by minimizing the distance between heat and fuel. I suspect that arranging the fuel reservoir so that it sits adjacent to some of the heat would be good. Like a donut fuel reservoir with the flame in the centre-bottom.

 

[Majorana]

Or some sort of passive single-stage heat shunt system.

Divert a small portion of the heat back to keeping the fuel warm.
[...]
You'd want to minimize loss by minimizing the distance between heat and fuel. I suspect that arranging the fuel reservoir so that it sits adjacent to some of the heat would be good. Like a donut fuel reservoir with the flame in the centre-bottom.

The fuel is already very warm (hot, actually): the paraffin of the tealights is totally liquid after a few minutes of burning. I think that's due to the small size (1") of the tealights and the very tight matrix (all of them touch each other).

 

[Majorana]

I was wondering whether some sort of catalyst, placed directly on the flame(s), could do the trick. Like a platinum (or platinum-plated) mesh. I am not an expert in catalysts, but I believe to remember that it's the general principle of operation: high temperature, unburned fuel (soot), air, and a catalyst.
Could it work?...

However, something that I don't understand is the recommendation of a Polish manufacturer of platinum grids, to AVOID putting a platinum mesh or grid directly on/through a candle flame...

 

[Majorana]

I think @DaveC426913 is on the right track.

You may (or may not) succeed in adapting a Primus Stove to use pressurized, melted paraffin from a candle as an alternative to kerosene fuel. You would need a second stove (or other candles) to keep the fuel tank hot. The chances of making that work may be small, but an experimental trial would not be expensive.

https://en.wikipedia.org/wiki/Primus_stove

View attachment 299370

Have you looked for affordable sources of ethanol in your country?

Primus stoves aren't readily available here, not even from internet stores. In addition, we must use the tealights "as they come": we cannot melt the paraffin out of them to reuse it, for a number of good reasons.
Bioethanol is still available for the moment, but we don't know for how long. The prices are ridiculously high, ranging from about 9 to 15 euros per US gallon.

 

[phinds]

Sometimes candle buying and gifting are a lot like the fruitcake gift during Xmas. The recipient doesn't know what to do with it and so gifts it to someone else the following year.

HEY ! As one of the three people left in North America who actually LIKES fruitcake, I resent that remark.

 

[DaveC426913]

...we must use the tealights "as they come": we cannot melt the paraffin out of them to reuse it, for a number of good reasons...

I'm curious what some of those reasons are.

Is it possibly because you're developing the accessory, while the consumer is left to provide their own tealights for it?

 

[phinds]

I'm curious what some of those reasons are.

I agree. Paraffin is paraffin

 

[DaveC426913]

I agree. Paraffin is paraffin

I suspect at least part of it has to do with what is in the OP's purview and what is left to the consumer.

If he's simply creating and selling a device, he does not have control over the step where the tealight needs to be decanted into a more useful vessel.

 

[Majorana]

I'm curious what some of those reasons are.

Is it possibly because you're developing the accessory, while the consumer is left to provide their own tealights for it?

I did not expand this particular aspect in the previous post because I didn't want to risk to make the thread drift off-topic, but...
I am not developing anything for commercial purposes. Shortly we'll find ourselves in a "war economy" without actually being at war. We the citizens are trying to get organized to survive the storm coming within a few weeks. Most people here live in condos (including me), so they are not allowed to light an open fire or install a wood-fired stove if the apartment is not provided with a connection to a vent pipe. A matrix of tealights is the perfect solution to cook when no other fuel is available or exploitable in a condo flat. But I am aware that most people (housewives, but not only) lack sufficient technical training, or haven't any at all. Replacing a tealight on a plywood board is quite simple, but finding a suitable heat generator (and its energy source!), melting the paraffin etc etc may not be readily feasible for everybody. I must keep things simple so that nobody gets injured and everybody can cook. I am NOT going to sell anything for commercial purposes. I just want to develop a cooking solution at give it to my fellow citizens, that's all.

 

[DaveC426913]

I am NOT going to sell anything for commercial purposes. I just want to develop a cooking solution at give it to my fellow citizens, that's all.

That was actually my assumption from the start, yes. It seemed implicit in your follow up posts.
It was not my intent to suggest consumers in the profit sense.

 

[anorlunda]

A Primus stove is almost as simple as you can get. If you can't buy or make something like that, I don't think there is anything simpler.

Cooking with the heat of yellow candles may be the best they can do.

 

[hutchphd]

A few comments.

1. Aladdin (brand) lamps; if I'm not mistaken, burn kerosene using a mantle and clever airflow to produce much more light than a standard kerosene lantern and with no soot. Is there some way to similarly utlize candle(s)?
2. My optimus stove (I think the same as primus) specified Naptha (Coleman Fuel in the states) or lead free gasoline in a pinch. More volatile than kerosene or paraffin.
3. I have used alcohol stoves on boats and they work remarkably well. Just a large circular wick in a stainless steel chimney

 

[Baluncore]

Rather than increasing the heat, increase the efficiency by reducing the heat losses.
1. Cover the cooking pot to reduce heat losses by evaporation as steam.
2. A thin stainless steel sheet stove, (or a cut tin can), to keep the heat close to the cooking container.
3. Warm the water and food before cooking. What animals do you have such as cattle or chickens ?
4. Pre-soak grain in water for 6 hours before final cooking. That will reduce the time heat is required to the end of the process.
5. Reduce and reuse the hot water used for cooking, it is soup or "silver tea".

 

[Majorana]

Maybe I got an idea! Will test it ASAP, keeping you posted