Dear Ron
Some are overly short. Here goes:
3.1 RWL: >Could one family coke for another (the idea that brought me
into TLUD design for wood in 1995).
CPP: We need far more than that. The inputs would be about 1 million tons a
year. There is no reason for one person to make coke. It would just increase
their fuel purchases. If they got their hands on it they would burn it (raw
coal).
[RWL3.1.2: Disagree. Should depend on the price of coke vs coal. Your
BLDD user, who strives to save coke, could have free heating if the price of
coke is high enough. For those of us worried about global warming, the making
of coke without use of the pyrolysis gases has to be about the most stupid
activity around.]
There is no market for coke. No one can afford it. The semi-coked fuels are 3-4
times as expensive as raw coal and no one can afford them either. There is a
plan to subsidise them. There nearly no evidence that semi-coked fuels create
lower emissions in a standard stove. Some are optimistic there will be a
reduction in smoke production relative to raw coal. I am not one of them.
<snip>
RWL3.2 >I'd rather do away with coal (and charcoal not put in the ground)
altogether - but I hate to think that the coke being used in UB was made badly.]
CPP: The present stove makes coke in the early phase of the fire then burns
it immediately afterwards. The smoke is from the ignition process. The
combustion during coking is quite good. There is a lot of misunderstanding
where the smoke comes from. Most NGO’s think it comes from coal during all
portions of the fire.
[RWL3.2.2: In the TLUD, one has to change the airflow a lot after the
char-making phase - or there is a lot of smoke. I presume you would have the
same problem. The Phillips stove people solved this with a variable speed fan.
CPP - At the moment fans are out. Electricity issues – 24/7 operation. TEG’s
might work…
Those of us interested in making char for Biochar simply close the system down
in one way or another. With a BLDD, you could do the same with a flapper
control in the chimney pipe - but I wonder if this second phase inability (or
failure) to control air flow isn't also the cause of a lot of smoke in UB.
We don’t want to purchase, transport and store 5 tons of fuel and then make
coke. Anything that can burn is burned: garbage, plastic, tires, oil-soaked
bricks, shoes, crates, and of course coal.
[RWL3.3: I am trying to determine if BLDD and TLUD are different during
start-up. Wood and "extremely dense smoke" sure don't have to go together.
CPP Most of the early emissions of smoke is wood burning (smouldering) badly
under a pile of cold wet coal. It is as much as 12 g / m^3.
CPP: I was referring to a conventional ignition. A wood fire is started then
coal is placed on it. That puts out the flame for some time, basically.
[RWL3.3.2: This doesn't sound like the cause of the smoke is the wood.
CPP In the beginning it is. Semi-coked briquettes in a traditional stove take
about 40% more wood as the minimum fire size for de-volatilised fuels is much
larger.
Any open flame wood fire does the same if you simply dump more on.
CPP Correct. That is the problem.
One of the beauties of a TLUD (and presumably a BLDD) is that one isn't
continually controlling power levels with fuel supply. I am pretty sure both
of these approaches can start with a tall enough fuel stack to last through a
night.
CPP – I hold that this is possible. It does not fit with current use patterns
for heating and cooking.
In the early days of the stove list, an Iowa corn farmer named Tom talked about
heating a barn with a TLUD design which was just a big tall stove pipe, with
suitably placed primary and secondary air holes. I can conceive of a housewife
getting free heating by selling the resulting coke each morning,
CPP – there is no market for coke. It is very hard to light and it far better
left where it is burning when the stove body is still hot.
RWL3.4 >I have gathered from the comments of John Davies, that coal was always
pretty bad until one had turned the coal to coke.
CPP - Not at all! We can get a smokeless fire within 2 minutes of ignition! The
GTZ 7 stove will go to 12 kW within 10 minutes of lighting. Raw coal is a
really good fuel in the right device. The present stoves have to be replaced.
The lighting and operation techniques have to be improved and the fuel should
be sized (25mm would be good).
CPP: Quite incorrect. The cleanliness of the burn depends heavily on the
availability of Hydrogen in the early fire. Later, retained heat can be used to
keep the coke burning.
RWL3.4.2: John Davies replied two days ago on this point - I thought
agreeing with my comment. Maybe we are talking about the traditional
approaches to combustion vs TLUDs and BLDDs? John?
[RWL3.5 >My hope is that with a controllable fan, one could start the wood
fires more readily. Even for a family without electricity, I would guess that
a PV-powered fan/blower system would prove cost-effective.]
CPP: A chimney is a fan without power. All it requires is some imaginative
stove development. In June during training we made very clean starting side
draft stoves which are almost as good as TLUD and can be refuelled at any time.
[RWL3.5.2: Have to disagree. A fan can put out a lot more air than any
(practical) chimney can.
CPP - A small fan does not move as much air as a modest chimney. A large fan
can move more. A natural draft chimney of 3 metres can maintain a pressure of
0.3 millibars while burning. That is quite enough to run a 15 kW fire.
Blacksmiths use fans/blowers and bellows for a good reason - to get heat -
which is what you said is necessary.
CPP - Sure.
I have no problem with side draft (basically not knowing what they are) -
but am pretty sure they can't make charcoal - which is my main focus still.
CPP - We do not want to make anything except heat, CO2 and H2O. The advantages
of a side draft stove are that it limits the burn rate and makes it far more
even, and it can be refuelled.
I do think BLDD's can make char - and that is my reason for continuing to hope
that your BLDD work is successful. Incidentally, Nathaniel Mulcahy does have a
continuous feed TLOD design. Nathaniel? I am guessing BLDD makes more sense
in UB, but maybe not.
<snip>
[RWL3.6 : >I have come to believe that the radically different World Stove
design (sometime called TLOD) is the cleanest of them all. If Nathaniel is
listening - have you ever tried coal? ]
CPP: It may or may not work. I have not seen one that could hold 8-10 kg of
coal. Coal going in is cold and that is a major issue. Then it gives off huge
amounts of volatiles if it is heated rapidly. Then the characteristics of the
fuel composition change dramatically. It is unlikely that a heated batch will
be manageable. The sidedraft stoves overcome all these problems.
[RWL3.6.2: Need Nathaniel again on larger systems - I am pretty sure he has
built ones larger than you ask for.
CPP - I think it is nowhere near doing what we need in terms of heat production
and burn time. Perhaps in future. The layout is not well suited to a high
volatiles fuel though.
The "heated rapidly" is controlled by limiting primary air (hole closures or a
fan/blower) in a properly designed TLUD (or TLOD. and presumably BLDD). Can
you give a cite on the sidedraft - and are you controlling primary air (and
separating from secondary air ) in these side draft designs.?
CPP - The side draft fire can be envisaged as a rectangular box with a fire lit
at one end where the chimney is also placed. A cast iron plate is placed over
everything. The fire ignites the coal and burns towards the far end of the
rectangle at a rate of about 80mm per hour. All new volatiles (smoke) have to
pass over an existing hot fire and are burned. It is very effective and cheap.
<2 snips on grannie's TLUD and one on storage and ceramic stove pipes in
nordic countries. I know that costs are a factor, but still wonder if some
energy storage could eliminate the need for all-night operation.>
CPP - I believe it is technically possible even in this cold climate. I have
slept in a house in Lesotho that was heated that way. It varied only 2 deg
throughout the year (solar heated mass wall).
[RWL3.7 : Then, I gather that the whole concept of energy efficiency and
passive solar is being scrapped for lack of a small stove? Weird reasoning.
CPP – Of course not! Energy efficiency is a major part of the interventions –
primarily through added insulation. Passive solar is completely unaffordable.
CPP: Obviously not. Solar was promoted and it is expensive. People earn
about $250 a year. People already have stoves when they pull into town on their
yak carts.
CPP – Correction – checked figures today: income about $250 a month PER FAMILY.
About 20% is spent on fuel.
[RWL3.7.2: I misunderstood. I thought we were talking UB's apartment
buildings. Is your interest now mostly urban or for the yurts or both?
CPP – the interest is for urban yurts (gers). Yurt is a Russian name for a ger.
I have been in yurts a few times (Colorado and Kyrgyzstan) but never during a
heating season. What is a typical daily consumption of coal in a yurt stove
and in a presumably larger apartment stove for a day with 0 degree C outside
temperature?
CPP - Gers typically burn 24 kg of coal a day in winter. Apartments are heated
with hot water systems using an HOB (heat only boiler) or are connected to the
power station via giant pipes.
.
The Chinese solar hot water systems (for space heating, not hot water) are
quite cheap - and (I'm guessing) might prove more cost effective that PV -
which I think are now pretty common for Yurt occupants. Certainly true in
Colorado.
CPP - For washing dishes perhaps. The small homes require about 150 to 200 MJ
per sq M per month in winter.
RWL3.8 >I see that Mongolia gets its rain in the summer - so Ulaan Baatar
(world's coldest capital) might be world's best place for solar heating.
CPP Not if you can’t see 100 metres through the thick coal smoke! Little
light reaches the ground in many places in Nov-Dec.
[RWL3.8.2: Whew. I hadn't that in mind. I'll return to this solar theme as
soon as you clean the place up. Good luck with that.
CPP – if I manage it will be the first time anyone cleaned up a city’s air
while still burning coal. So far people changed fuel rather than address to
root problem which is ignition emissions of the stove. Today we worked out that
there will be a substantial improvement in air quality if the poor were all
given a lot more coal to burn so they could a) stay warm all year and b) reduce
dramatically the number of times they lit the stove. When running, the stoves
produce very little in the way of smoke.
I am afraid that I believe the system will be better off if there can be
electric resistance baseboard heating with the coal used in a central station
(and that is pretty wasteful, admittedly.
CPP – there is not enough generating capacity to do that and it is 100% coal.
Anyway, less total pollution is produce by burning in the houses compared with
running a power station and using electricity. We did the math on that in JHB
years ago. Space heating? Burn coal cleanly at the point of use.
Or how about wind in the UB area?
CPP – not much. There is a wind farm going in – vast subsidy that can not
longer be applied to improved stoves and fuels….
Or imported oil? (Kirk Smith's recommendation to displace wood use at one
time. Maybe still. Guessing he would agree on oil being cheap for UB, if you
consider ALL the costs.)
CPP – Unaffordable. There is no option but coal at present.
There must be many epidemiological studies on life times and cancer in UB.
How bad? I think there needs to be a study on how cheap coal use is in UB,
if one doesn't exist.
CPP - Health studies abound. What does not abound are good stoves or any clue
how to build them. This is not actually a very difficult problem to define and
solve. The start up emissions are almost all of it, and people who have little
fuel tend to light a small amount more frequently. People who use mass storage,
ditto because they are storing heat and relight the stove a few times a day.
Unfortunately for everyone, there is a push to use processed expensive fuels in
the belief (with very little justification) that it will reduce emissions.
Testing last year showed a 35% INCREASE. Testing this year by one guy with a
lot of experience showed a drop, but when we examined the figures closely they
did not add up – we could decide quite what he was doing to get his outputs so
we will test the fuel and method of lighting to see. Even at equal emissions,
there is no reason to triple the fuel price plunging hundreds of thousands of
people into a frozen state. There is in my view no reason to implement an
expensive, unsustainable solution that reduces pollution 50%. We should aim for
a 98% reduction as 99.9% has already been demonstrated without even having an
official product development project yet. That level of reduction is only
possible by burning raw coal with enough H2 in it to light quickly and respond
early to a strong draft. Coke doesn’t do that. In fact coke is almost
unlightable. Try it some time. Bring a lot of wood…
We are looking at the moment for documentation proving that really poor people
light their stoves more frequently that rich people. If so we should ask for
them to be give more coal vouchers because a) they are cold and b) they will
stop re-lighting the fire so many times per day and rather keep the stove
burning. It is a very interesting situation!
FYI a Mongolia emits on average about 2 tons of CO2 per year from fossil
sources. Most space heating is wood-fired, but not in UB.
Regards
Crispin
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