[Stoves] re-kindling stoves

[Richard Stanley]

er, what again, about side feeding... ???

On Dec 22, 2010, at 3:56 PM, ajheggie at gmail.com wrote:

> On Wednesday 22 December 2010 00:06:35 Crispin Pemberton-Pigott wrote:
>>>> That means training people not to do what comes
>>>> naturally (let the stove die out and refuel and relight from
>>>> scratch).
>> 
>> Yeah. That is what I meant.
> 
> ...and that's where I saw a point for confusion.
> 
> It could read as letting the fire die out and then refuel being what comes 
> naturally.
> 
> In fact what comes naturally is to dump another batch of fuel on top of 
> the glowing embers, this quenches any existing flame as the new load 
> heats up and subsequently the new load starts pyrolysing with insufficient 
> temperature or flame to burn the offgas.
> 
> Pellet stoves get around the problem by feeding in a small amount of fresh 
> fuel such that a continuous flame is maintained over the whole firebed. 
> Everything has to pass through the flame.
> 
> As a tlud maintains a fairly constant power if the primary air is well 
> controlled then extended burn time can be got by increasing the height of 
> the fuel.
> 
> As this is often not practical there are a number of ways people have 
> tried to get around it. Paul Anderson went for fuel cassettes that were 
> pre loaded and alternated but it has not been mentioned recently.
> 
> Top lighting for a clean start has been advocated by many, I think the 
> masonry stove association mentioned it when [stoves] was young. TLUD is a 
> special case where the progressive descent of the pyrolysis front 
> provides an air free offgas that shields the char formed above from 
> combustion. Change the conditions slightly by slowing the front or 
> increasing the air supply and this char is consumed. I've seen no mention 
> of particulates under these "no residual char" conditions. Generally 
> particulates are formed in the secondary combustion area. From a long 
> term health point of view particulates remain the bigger problem over 
> straight thermal conversion efficiency.
> 
> Richard asked:
>> Please tell me why adding a side feed feature to this stove would not
>> greatly improve the cool down start up problem /smoke/ you are
>> experiecning with your batch feed  process ? 
> 
> Richard I don't know this stove, as Crispin has pointed out a modification 
> made to steam locos was to auger a "molehill" of coal from under the 
> firebed so the curtain of fire wasn't disturbed by a fresh cold batch of 
> coal being dumped on it.
> 
> Given we seem to be looking at 5kW stoves, that's about 1kg of drymatter 
> per hour. What does one of your holey briquettes weigh when dry? Part of 
> the way a tlud works is to do with the change in buoyancy of the gases as 
> they evolve and then heat up. As we have discussed before I'd like to try 
> making a semi continuous burner using holey briquettes in much the same 
> way a rocket fuel in fed by pushing longer sticks into the fire chamber. 
> As I see it we need to keep it as close coupled as possible because with 
> these small devices if heat is lost in the primary combustion zone then 
> the gases in the secondary  zone have lost temperature and are diluted by 
> CO2 and N2. The tlud avoids this problem by minimising the combustion 
> products of char.
> 
> AJH
> 
> 
> 
> 
> 
> 
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