[Stoves] Wood fired, two-stage gasification employed

Thu Aug 4 02:38:41 CDT 2011

Dear Crispin

----- Original Message ----- 
From: "Crispin Pemberton-Pigott" <crispinpigott at gmail.com>
To: "Discussion of biomass cooking stoves" <stoves at lists.bioenergylists.org>
Sent: Wednesday, August 03, 2011 11:53 PM
Subject: Re: [Stoves] Wood fired, two-stage gasification employed

> Dear Robert and anyone who can help:
>
> The emissions are given per cubic metre. It is likely that the flue gas 
> measurements are normalised to a certain oxygen level, for example 7% or 
> 11%. Does anyone know what the O2 level is when reporting the CO limit, 
> for example?

When adjusting the excess air on an oil burner, one can use a Bacharach 
Smoke Spot Tester, and simply reduce the excess air to a point where one 
gets a Smoke Spot Reading of #1. This is a very simple way of minimizing 
excess air for a burner system with a given fuel/air mixing system. However, 
it does not necessarily give a consistent degree of CO, or O2, in that it is 
using the presence of a small amount of soot/ to indicate that the excess 
air is at the lowest level attainable for that particular system. Flame 
retention head oil burners thus give a lower O2 content in the flue gas, 
than the older oil burners, with the same Smoke Spot Reading.

Accordingly, I would think that unless there is a specific Standard that 
specifies the O2 level at which the CO is measured, two different stoves or 
furnaces reporting the same CO levels could have very different O2 and Smoke 
Spot Readings.
>
> The number is not meaningful unless the dilution value is known. Because 
> of the confusion created by having in Europe a different dilution factor 
> for each fuel I advocate that all emissions be calculated at 0% O2 (no 
> dilution at all) because a) it is easy to calculate and b) everything is 
> directly comparable (different fuels and stoves).

Different fuels, with different combustion characteristics, and with 
different combustion systems, will require different levels of excess air to 
get an acceptable set of "Stack Results", that are good for longer term 
operation. One Stove/Furnace may be able to get the desired CO level with 
say 1% Oxygen in teh Stack Gas, while another system may need say 5% O2 to 
get the same CO Level. Obviously, both systems would "pass the CO Test", but 
the latter system would have lower efficiency, when tested by the CO2 and 
Stack Temperature method. I don't think it is possible to have a meaningful 
test system based on 0% Oxygen in the flue gases, in that a very small 
oxygen analysis error could yield a very large change in soot and CO 
presence, depending on specific system fuels and designs.  HOWEVER, it would 
be very easy to do a "Standardized Calculation at the Equivalent of 0% O2". 
The problem here is that "reality is all over the place"... Automobiles 
often met EPA Pollution Standards by adding a dilution air blower to dilute 
the CO, Hydrocarbons or Particulates in the tailpipe down to the "acceptable 
grams per M^3".   The total pollution per unit of fuel was excessive, but 
per unit of exhaust gas, it met the standards.

> Whatever the dilution factor is the corrected emission numbers is per M^3 
> seem pretty high.

The Test Protocol should be set up to capture and report the data necessary 
to yield the information required to decide if the stove/ furnace system was 
adequate for the intended purpose or circumstance. There is not one, but 
many factors, that should be measured and reported, to enable one to compare 
various stove/furnace systems.
>
> Interesting.

Indeed!! On the Stoves List, we all want "The Perfect Stove" that has 98% 
efficiency, 0% Emissions of any sort, can burn any fuel, looks nice, is easy 
to use, does not need a chimbey or batteries, costs less than $5, and can be 
locally manufactured. However, on the Biochar List, such a "Perfect Stove" 
would additionally have to produce biochar. :-)

Best wishes,

Kevin

>
> Regards
> Crispin
> -----Original Message-----
> From: "Robert Taylor" <rt at ms1.hinet.net>
> Sender: stoves-bounces at lists.bioenergylists.org
> Date: Thu, 4 Aug 2011 07:49:07
> To: Discussion of biomass cooking stoves<stoves at lists.bioenergylists.org>
> Reply-To: Discussion of biomass cooking stoves
> <stoves at lists.bioenergylists.org>
> Subject: Re: [Stoves] Wood fired, two-stage gasification employed
>
> Here's a rough and ready translation of the German in the two pages that
> Martin links to:
>
> Umwelttechnik:
>
>
>
> Environmental technology
>
>
>
> To reduce environmental loads, the legal limits on CO and fine particulate
> emissions have been redefined. The planned limits are:
>
>
>
> Fine particulates:
>
> Legal limit from 2008: 100 mg/m3; from 2015: 40 mg/m3
>
> xeoos Twinfire emissions, 2008: 22 mg/m3
>
>
>
> Carbon monoxide:
>
> Legal limit from 2008: 2000 mg/m3; from 2015: 1250 mg/m3
>
> xeoos Twinfire emissions, 2008: 625 mg/m3
>
>
>
>
>
> The xeoos, with its patented combustion process, not only meets these
> values, but goes far below them, even at partial or minimum loads. This is
> achieved by:
>
>
>
> - Burning exhaust gases at 1000-1200 deg C
>
> - 180-degree inertial separation of suspended particulates from exhaust
> gases in lower combustion chamber
>
> - intelligent air routing inside stove leads to maximum heat transfer into
> room
>
>
>
>
>
> Brenntechnik:
>
>
>
> Combustion technology
>
>
>
> In the xeoos Twinfire combustion process, the exhaust gases created by the
> burning of wood in the upper combustion chamber undergo an afterburn at
> temperatures of 1000-1200 deg C and are thus converted into additional 
> heat
> and energy. In this way the xeoos achieves:
>
>
>
> - efficiency of over 90% throughout the burn period
>
> - up to 40% less ash generation for the same heat output, compared to a
> xeoos fireplace stove not operating in twinfire mode
>
> - up to 40% lower fuel consumption for the same heat output, compared to a
> xeoos fireplace stove not operating in twinfire mode
>
> - extremely low proportion of fine particulates, and very low proportion 
> of
> CO, in exhaust gases
>
> - consistently low emissions even at partial or minimum load
>
>
>
> Facts:
>
> - body in steel sheet 4 mm thick
>
> - front frame in gray cast iron
>
> - combustion chamber cladding in vermiculite
>
> - combustion chamber floor in special refractory* material
>
> (*the meaning of the German word is probably more specific than this; see
> "Schamotte" in German Wikipedia)
>
> - double floor in highly heat resistant stainless* steel
>
> (*"Edelstahl" is usually translated as "stainless steel", but not every
> Edelstahl is stainless, and not every stainless steel is an Edelstahl; the
> term covers various special-purpose steels, as defined by the relevant
> standards)
>
> - twinfire grate in highly heat resistant stainless steel
>
> - ash box in highly heat resistant stainless steel
>
> - simple, ergonomic control via two thermally decoupled control elements
>
> - free choice of top or rear flue outlet
>
> - all stoves can be equipped with xeoos adaptor for external combustion 
> air
> feed
>
> - xeoos stoves can optionally be equipped to be rotatable
>
> - the xeoos burns with normal chimney draft
>
> - five years' warranty on body
>
>
>
>
>
> Figure:
>
>
>
> Twinfire tuner
>
> Door handle/Twinfire starter
>
> Upper combustion chamber
>
> Twinfire grate
>
> Lower combustion chamber
>
> Ash box
>
>
>
>
>
> HTH
>
>
>
> Robert Taylor
>
>
>
> ----- Original Message ----- 
> From: "Boll, Martin Dr." <boll.bn at t-online.de>
> To: <stoves at lists.bioenergylists.org>; "'Crispin Pemberton-Pigott'"
> <crispinpigott at gmail.com>
> Sent: Thursday, August 04, 2011 6:10 AM
> Subject: Re: [Stoves] Wood fired, two-stage gasification employed
>
>
>> Crispin,
>>
>> There is another two-stage top to bottom burning room-heating-stove. I 
>> saw
>> it some years ago here in Hatzfeld-Reddighausen, Germany, in the 
>> show-room
>> of the producer.
>> It has natural draft!
>> The website is in German, Swedish and Polish, not in English. But the
>> pages
>> on bottom have pictures and short technical terms.
>> It is certainly even eco and bio but they do not make so much music about
>> that.
>> http://www.xeoos.de/technik/umwelttechnik.html
>>
>> http://www.xeoos.de/technik/brenntechnik.html
>>
>> - Interested in your meaning -
>>
>> Kind Regards
>> Martin
>
>
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