Saturday, January 26, 2013

converting appliences from LPG or NG over to Hydrogen gas

These are some idea's I pulled from the internet for converting
 home and rv appliances over to hydrogen from propane or natural gas 
David Booth and Walt Pyle
Converting conventional stove top burners to run on hydrogen is 
a simple process. Knowing the proper handling procedures of 
hydrogen will make your installation safe and efficient.
Much of the research that I refer to in this article was 
performed by Roger Billings, N. R. Baker, and their associates of 
the now defunct Billings Energy Corporation. This pioneering 
work was done mostly in the 1970s. An early research endeavor 
involved conversion of all the gas appliances on a Winnebago 
recreational vehicle from propane to hydrogen operation. To 
demonstrate hydrogen's practicality even further, five natural 
gas appliances were converted to hydrogen. This multi-phased 
project in Provo, Utah was called the Hydrogen Homestead. 
Included among the appliances converted for this home were an 
oven, a range, a barbeque, a fireplace log burner, and the 
booster heater for the home's heat pump system.
Theory before Practice
Hydrogen burns differently than either propane or natural gas. 
In particular, hydrogen's rate of diffusion and flame velocity 
are roughly ten times or greater that of propane or natural gas. 
Diffusion rate measures how long it takes a gas introduced in 
one side of a room to be detected on the other side. Flame speed 
is how fast a flame grows to burn available fuel. 
Flashback of the flame into the primary mixture of fuel gas and 
air must be prevented in all burners. This is typically achieved 
with natural gas and propane by adjusting the fuel velocity so 
that it is higher than the normal flame velocity. The flame 
velocity of hydrogen is too high for this technique to be 
practical. Another flashback control strategy employs burner 
ports with a minimum quenching diameter which theoretically 
will not allow the flame to pass back through the port. In 
practice, however, it is very difficult to make the holes small 
enough to quench a hydrogen flame. Fortunately, flashback can 
be minimized by preventing hydrogen from mixing with air 
before the burner port. Some flashback may still occur creating 
a loud popping sound but this noise is usually harmless.
Figure 1 shows the principal parts of a typical range top burner 
used with conventional gaseous fuels. Usually the fuel streams 
in through a gas orifice with a delivery pressure of probably 
between 3-15 inches of water column. Primary air is then 
drawn in with the gas stream through an air-gas mixer. 
Secondary air openings to mix in more air may or may not be 
present. Finally, as the mixture exits through the burner ports 
combustion occurs, if a spark ignition source or pilot light is 
Horse of a different color
This burner design will not suffice for hydrogen in an unaltered 
state. Burners optimized for hydrogen combustion require that 
undiluted hydrogen be delivered directly to the burner ports 
without primary or secondary air mixing. So, if we are trying to 
work with an existing burner in a typical gas appliance, we will 
have to find a suitable method to seal off any openings that 
were installed for this purpose. One method won't work in all 
instances. We used silicon sealant with stainless steel tape 
and ring clamps in one recent alteration, but this simple 
Coleman stove conversion hasn't been subjected to long term 
use as yet. The actual openings we are referring to may be an 
integral part of a cast iron body. Or the primary air openings 
may be a modest distance from the burner head in an aluminum 
delivery tube with an adjustable closure.  
From scratch
It is not inconceivable that one might rather opt to build a 
simple burner and direct fuel delivery apparatus from the 
ground up, rather than deal with the problem of sealing off a 
nagging assortment of useless holes. Burners and their attached 
parts get hot, and transfer heat readily through conduction. 
Sorry, duct tape and chewing gum won't cut it.
Our first attempt at a simple hydrogen conversion utilized a 
rudimentary two burner range of cast iron construction. After 
we tossed the existing burner assembly, and removed the 
screwed on brass orifice, a threaded adaptor was exposed. To 
this we screwed on a 1/4 inch straight coupling followed by a 
short length of black iron pipe of the same diameter. Don't use 
galvanized pipe, because of the fumes that will be released at 
high temperatures. Then we installed a 90 degree elbow 
followed by a short vertical nipple of more pipe. Next a 1/4 
inch fitting shaped like a cross with four female threaded 
openings was drilled and tapped to create a fifth hole. This 
threaded onto the short vertical nipple, and four slightly longer 
nipples of equal length extended out radially from the 
remaining holes. Finally, these terminated in threaded end caps. 
A drill press is almost essential for drilling a series of very 
fine holes which will line up along the top of the radial burner 
arms, and through the top of the cross. Ideally, these burner 
ports would have a 0.0225 inch (0.057 cm) diameter or less, 
which is the minimum quenching diameter.
The catalytic advantage
It has been observed in early experiments that the flame 
combustion of hydrogen/air mixtures can lead to unacceptable 
levels of nitrogen oxide (NOx) pollutant emissions. The primary 
end product of hydrogen combustion is simply water vapor. 
However, if the temperature of combustion exceeds the 
threshold level of 2400øF (1315øC.), a significant amount of 
oxygen and nitrogen from the air may react and form this 
unwanted byproduct. This also occurs with natural gas 
(primarily methane), propane, and other hydrocarbon fuel 
Fortunately, you can use a catalyst to lower the combustion 
temperature thus preventing the formation of nitrogen oxides. 
The catalytic material is not used up or altered in any fashion 
in the process.
There are two catalytic conversion techniques which succeed in 
producing negligible levels of NOx emissions. The first 
approach uses experience gained by Billings and his associates 
with flame assisted catalytic burners. Their conversions 
utilized the catalytic properties of stainless steel at elevated 
temperatures. Later, in another article, we'll describe the 
conversion of a catalytic space heater which optimizes 
"flameless" combustion with a small amount of platinum.
Flame assisted catalysis
The technique developed by the Billing's research team to 
reduce NOx formation relies on controlling two interacting 
phenomena. First, as has already been described, hydrogen/air 
mixing is inhibited by blocking off any primary air openings. 
Second, a stainless steel wire mesh is arranged tightly around 
the circular burner head or radial burner arms. 
Where does one find stainless steel wool or wire mesh? Look 
for stainless steel pot scrubbers in a large, thoroughly stocked 
supermarket in the housewares section.
Getting our NOx off
This stainless steel wool blanket around the burner actually 
serves two complimentary functions. It inhibits the mixing of 
air and hydrogen thus producing a zone immediately surrounding 
the burner head where the concentration of hydrogen is very 
high and the concentration of air is very low. The wire mesh 
should be thick enough so that the flame does not radiate above 
it or out too far laterally. If there isn't a sufficient amount of 
stainless steel mesh, the catalytic capability and ability to 
negate NOx production could be lost.
Stainless steel also works as an excellent catalyst for 
hydrogen combustion. Hydrogen and oxygen are thus combined on 
the surface of the catalyst at a slower rate than would occur 
without the catalyst. This eliminates the high temperatures 
that are produced when a large fraction of hydrogen is 
combusted in a small area. The result of the lowered 
combustion temperature is that nitrogen oxides are virtually 
eliminated. The steel wool proceeds to glow bright red even at 
these temperatures, indicating that the otherwise invisible 
hydrogen flame is present.
According to Roger Billings in The Hydrogen World View, flame 
assisted catalytic technique can lower NOx emission from 
hydrogen combustion in range burners, ovens, and space heaters 
to negligible levels. The resulting data showed NOx emission 
levels between 1 and 5 parts per million (ppm) for a catalytic 
assisted burner. This can be compared with 40 ppm for 
conventional range burners operated on natural gas and 250 ppm 
for a hydrogen burner without a catalyst.
More to come
We need to build a sound understanding, before we can 
confidently proceed to implement hydrogen for scores of 
potential uses. If you'd like more information, dig into the 
further reading section at the end of the article. 
In the next issue, we will delve into a technique for 
transforming the chemical energy stored in hydrogen to 
available heat energy without the presence of a flame. This 
form of combustion is possible when hydrogen is oxidized in 
the presence of certain specific catalysts such as platinum. 
This is considered "pure" catalytic combustion. Water vapor is 
the only byproduct along with heat, so no venting of the 
appliance may be necessary (if means to prevent oxygen 
depletion for the room air is assured).
We're in the process of putting together a system that will 
convert renewable solar electricity into the storable chemical 
energy of hydrogen through the process of electrolysis. The 
process is still underway but we will offer detailed accounts 
of our endeavors in forthcoming issues. 
Spreading the invisible flame
There may well be a wealth of undiscovered and untapped 
hands-on information available from other hydrogen 
enthusiasts out there scattered through the countryside. If you 
are among the other backyard tinkerers and hydrogen pioneers 
who are putting theory into practice, let us hear from you. The 
time has come to spread the word about hydrogen's unique 
advantages. It is clearly the hands-down winner among the 
possible candidates of alternative fuels for the future in our 
environmentally beleaguered world.
A note on safety
Remember that storing pure hydrogen can be regarded as a 
relatively safe procedure, but storing hydrogen /air or 
hydrogen/oxygen mixtures is foolhardy and strictly inadvisable.
Authors: David Booth, Alternative Energy Engineering, POB 391, 
Miranda CA 95553 ù 707-923-4336
Walt Pyle, WA6DUR, Richmond, CA ù 510-237-7877
Further Reading
1. Oxides of Nitrogen Control Techniques for Appliance 
Conversion to Hydrogen Fuel, technical paper #74003, by , N.R. 
Baker is available from the International Academy of Science, 
26900 Pink Hill Road, Independence, MO 64057 (816) 229-3800.
2. Hydrogen Homestead, technical paper #78005, by Roger 
Billings is available from the International Academy of 
3. Fuel from Water by Michael Peavey is available from 
Alternative Energy Engineering for $16.
4. The Hydrogen World View by Roger Billings is available from 
the International Academy of Science.