[Stoves] [Fwd: Re: Stove gas testing]
frank
frank at compostlab.com
Mon Sep 17 16:16:17 EDT 2007
Stovers,
The fact that these sensors using SnO2 are not at all specific to the
gases they say it is designed to detect is a benefit to us. But I do get
upset with the method they market the product.
FYI First I determined the most sensitive gas flow is about 100 mls
per minute and any higher and the gas gets past the 350 deg. C cell with
much less time to do-its-thing and respond. Also the company I purchased
the detector from has a calibration service that for a mere $500 US
dollars they will calibrate it for us. Lets seee..... The detector is
sensitive to O2 concentrations, flow rates, other gases -- how can
they calibrate it for our use????? We must calibrate it ourselves as
we use it. I suggest we agree on using CH4 as a calibration gas because
I think that is the easiest gas for us to get delivered to our homes.
I think when we measure the stack gases there will be no H or CH4 (?)
because most will have been used up in secondary combustion. CO needing
a higher temperature (?) is likely the gas we are measuring but I still
think there could be lots of other deoxidizing gases (organic compounds)
the detector is measuring. And if we measure the gases between primary
and secondary ( as I plan to do) we will know the gases we will be
measuring are a make-up of a wide range of compounds.
I suggest::: When using SnO2 sensors we report our findings as
'deoxidizing gases (as CH4)'. or 'dOxG (as CH4)'. Other
suggestions?. We could standardize using CO, H or CH4. I suggest CH4
because that is the gas I think most working in shops or backyards could
get. Try having a tank of CO or H sent to your home - I think you may
have problems.
So having one detector that will measure all deoxidizing gases (dOxG)
for only a couple hundred dollars will mean all can get into fuel and
stove testing at a small cost. I think the goal is having the 'dOxG'
stack gas as low as possible and having the dOxG between the primary and
secondary as high as possible per surface ares of the cross section of
the burner. At this stage in my testing I don't think it important to
know what type of dOxG I am measuring - just a relative amount. And I
think we can no longer report it as a specific gas like CO, CH4 or H now
knowing how unspecific the detector is. Let the ones that have the more
expensive equipment report as specific gases if their equipment can do
that.
Open to suggestions
Frank
B.C. Romero Orellana wrote:
>
> Maybe it can help....
>
> *Sensors and Actuators B: Chemical*
> <http://www.sciencedirect.com/science/journal/09254005>
> Volume 57, Issues 1-3
> <http://www.sciencedirect.com/science?_ob=PublicationURL&_tockey=%23TOC%235283%231999%23999429998%23152811%23FLA%23&_cdi=5283&_pubType=J&view=c&_auth=y&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=048249f3f76392877ae8d2b325845176>,
> 7 September 1999, Pages 108-114
>
> Abstract
>
> Technology associated with both catalytic and semiconductor-based gas
> sensors has been combined to produce hybrid devices capable of
> detecting low levels of combustible gases. First-generation
> non-selective sensors, which respond to a wide range of reducing gases
> including hydrogen, carbon monoxide, lower hydrocarbons and ethanol
> vapour, were obtained by coating narrow diameter platinum wire coils
> with a low resistivity tin dioxide-based formulation. As in the case
> of catalytic sensors, /semi/conductor-based pelli/stors/ (semistors)
> are typically operated in a bridge-type circuit. However, in contrast
> to catalytic sensors, which are used to detect percentage levels of
> combustible gases, semistors are responsive to sub-100 ppm
> concentrations. Optimisation experiments have been carried out on
> factors affecting performance, such as sensing layer composition, coil
> pitch and firing time. A further study on the effects of incorporating
> an additional catalyst-containing surface filter layer has led to the
> development of a second-generation methane-selective sensor.
> Undesirable humidity and ambient temperature effects, normally
> associated with tin dioxide-based sensors, can be eradicated by
> operating a semistor in conjunction with a compensating element. This
> utilises a filter layer, which removes all target gas response while
> retaining the same humidity and temperature dependence as the sensor
>
>
> *Sensors and Actuators B: Chemical*
> <http://www.sciencedirect.com/science/journal/09254005>
> Volume 117, Issue 2
> <http://www.sciencedirect.com/science?_ob=PublicationURL&_tockey=%23TOC%235283%232006%23998829997%23629515%23FLA%23&_cdi=5283&_pubType=J&view=c&_auth=y&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=1ab6e22437088cdd3f05be2f8f4fd33d>,
> 12 October 2006, Pages 420-425
> Transducers '05 - Selected Papers from TRANSDUCERS '05. The 13th
> International Conference on Solid-State Sensors, Actuators and
> Microsystems
>
> In the present study, LaCoO_3 perovskite was used as an active filter
> to suppress the sensitivity of a Pt/SnO_2 sensor to CO and C_2 H_5 OH.
> A sol–gel procedure was used for the preparation of SnO _2 fine
> powder, which was impregnated with hexachloroplatinic acid to obtain
> 1.0 wt% Pt on SnO_2 . The LaCoO_3 perovskite fine powder was prepared
> by citrate method, using nitrate precursors of La and Co. LaCoO _3 is
> an effective oxidation catalyst for oxidation of both carbon monoxide
> and ethanol at temperatures lower than 250 °C. However, the catalyst
> does not convert methane at temperatures as high as 400 °C. The Pt/SnO
> _2 is highly sensitive to ethanol and shows a significant sensitivity
> to CO. The perovskite filter eliminates the sensitivity of the sensor
> to CO and C_2 H_5 OH, making the sensor highly selective to methane in
> the presence of CO and ethanol in air.
>
>
>
> On 9/14/07, *frank* <frank at compostlab.com
> <mailto:frank at compostlab.com>> wrote:
>
> Stovers,
>
> FYI
> I purchased both a CO, CH4 detector planned for measuring the
> pyrolysis
> gases from the primary combustion in a TLUD (along with CO2, and O2).
> After about a thousand dollar of equipment and set up equipment (and
> hours of work) I discovered the CO, CH4 and H2 detectors are all the
> same with, perhaps the difference being the temperature the detector
> chamber goes to. I had them assembled in a series and when I injected
> CH4 both the CO and CH4 indicated a reading. Injecting the CO
> and both
> gave a reading. So there is no way I know of when using these type
> detectors to make specific gas readings. I do not have a H
> detector but
> found out that it is also same detector so cannot be used. The
> only ones
> that seem to work well is the CO2 and O2 detectors. Using any one
> of the
> others to measure a mix of CO, CH4 and H.
>
> Not sure yet but I think the FT-IR is the way to go ???? but
> that is
> way out of my R&D budget range.
>
> Anyone have any other suggestions?
>
> Thanks
> Frank
>
>
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>
>
>
> --
> Carolina Romero
--
Frank Shields
Soil Control Lab
42 Hangar way
Watsonville, CA 95076
(831) 724-5422 tel
(831) 724-3188 fax
frank at compostlab.com
www.compostlab.com
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