035007
DWFC: New Fuel Cell Autonomously Operates with Only Air Supplied
"Techno Bank Corporation" in Japan has proprietary technologies
for generating a large amount of hydrogen by hydrolyzing MgH2 fine powder.
The MgH2 fine power has particle diameters in order of nm.
The nano particles of the fine powder are coated with firing prevention
films and water-proofed. The nano powder thus processed is packed into
a cassette, and is safely transported and stored.
The cassette is combined with a suitable fuel cell, and assembled in an
integrated form. The company named the thus assembled fuel cell system
as "direct water fuel cell (DWFC)".
Note that DWFC operates while being supplied with only air.
Water produced during the fuel cell operation is circulatively supplied
to the MgH2 hydrogen generator cassette, and used for the MgH2 hydrolyzing
process to generate hydrogen.
The amount of hydrogen generated is controllable.
The electric conversion efficiency of the DWFC is about 70%.
This figure is much higher than about 35% of the DMFC.
It is a matter of course that the company's hydrogen generation technologies
are applied to FCVs (fuel cell vehicles) and hydrogen vehicles.
Those technologies-based products, including the MgH2 nano powder cassettes,
have already been manufactured and sold under the project, called "Magcycle
Project".
The company has received some inquiries from relative big companies, including
automobile manufacturer, inside and outside Japan.
1. MgH2 Based Hydrogen
Generation
MgH2 nano powder is hydrolyzed. Bittern (MgCl) is used as a reaction
accelerator in the hydrolyzing process.
As the result of hydrolyzing MgH2 nano powder, 8 wt% of hydrogen is
generated and 7 wt% hydrogen is generated from hydride.
The hydrogen is generated more efficiently than in the case of using
a known aluminum hydride complex.
In an experiment conducted, MgCl of which the reaction automatically
progresses at normal temperature and normal pressure, was used as the
reaction accelerator.
The hydrolysis reaction was promoted by increasing the temperature from
normal temperature to 80°C by self-heating in the reaction.
1,300 cc of hydrogen was produced from 1 g of MgH2.
The clean energy system using magnesium has been under development by
Tokyo Institute of Technology and Mitsubishi Corporation. The development
is performed under part of Japanese Academic Research Collaboration
project.
When comparing with the clean energy system, the company's technologies
are superior at least in the following points: 1) the hydrolysis may
occur at normal temperature and 2) The amount of hydrogen generated
is larger than that by the clean energy system.
Mg(OH)2 which is produced after MgH2 generates hydrogen may be reduced
by a pump laser, and may be used again as medical/industrial raw material,
soil additive, flame retardant, and the like.
MgH2 Nano Powder
Mg is reduced from MgO. Laser was used for the reduction.
MgH2 nano powder in which hydrogen atoms are placed among Mg molecules
is formed.
The nano powder is added with firing preventing film and waterproofed.
The nano powder thus processed is safe in its transportation and storage,
and packaged into cassettes.
Consumers can buy the MgH2 cassettes at supermarkets, convenience stores,
etc.
It has been known from old time that Mg generates a large amount of
hydrogen by the hydrolysis reaction using the catalyst.
In case where the fine powder having the particle diameter of only about
50 mm, commercially available, is used, even if one tries to carry out
the hydrolysis of Mg using the catalyst at normal temperature, a magnesium
hydroxide (Mg(OH)2) film is formed on the Mg surface and stops the hydrolysis
reaction.
To continue the hydrolysis reaction, it is necessary to take some action
to constantly remove the Mg(OH)2 film. Exemplar actions taken for this
end are use of a strong acid reagent and external apply of heat.
A possible solution to the problem we reached was to reduce the particle
diameter of the Mg fine powder to be in order of nanometer.
The approach succeeded. When the Mg powder is pulverized into nano particles,
the specific surface area of the Mg particle considerably increases
and the total interfacial reaction calorie increases.
With the increased interfacial reaction calorie, the hydrolysis reaction
automatically progresses.
It is assumed that the particle diameter of the Mg powder is 1 mm and
the specific surface area is 1. On this assumption, when the particle
diameter is 20 nm, the specific surface area is about 45 m2/g (about
150 times). The interfacial reaction calorie proportionally increases.
2. Power and Hydrogen
Generation Technology
A positive electrode, a negative electrode and an electrolyte are provided
within a cassette. MgH2 is used for the negative electrode active material.
Ionized Mg and electrons are received by the positive electrode. A load
is connected between the positive electrode and the negative electrode.
An output voltage of the device thus constructed, as an electricity/hydrogen
generator, was 2.7 V.
7 wt.% of hydrogen is generated from the hydride fixed in the interstices
among the Mg crystals. An amount of hydrogen gas generated can be controlled
by controlling current flowing through the load.
The electricity/hydrogen generator, when serving as the electricity
generator, operates at the conversion efficiency of more than 80%. When
it is combined with a fuel cell (PEFC) to form a direct water fuel cell
(DWFC), the DWFC operates at the conversion efficiency of more than
50%.
3. DWFC (direct water
fuel cell)
The DWFC is a combination of (MgH2 based hydrogen generation (+ electricity
generation) + fuel cell (PEFC).
In the DWFC, the water produced during the fuel cell operation is used
for the hydrolysis process to generate hydrogen from MgH2.
The DMFC self-sustains itself with the hydrogen the fuel cell produces,
and automatically operates with the supply of only air.
The electric conversion efficiency of the DWFC is about 70%, while that
of the DMFC is about 35%. This high conversion efficiency leads to much
reduction of the fuel cell size per unit electric power.
4. Others
"Chemical
Engineering" (Chemical
Engineering Magazine in USA)
"Hydrogen storage technology using MgH2"
Deliver an invitation speech in "Energy
Innovation Conference",
August 2007, San Francisco.
For more and exact inofrmations, please mailto:info@techno-bank.co.jp
URL (English):
http://www.techno-bank.co.jp/technology/index_technology.htm
URL (Japanese):
http://www.techno-bank.co.jp/technology/jp_index_technology.htm
Keywords: magnesium hydride, MgH2 nano
power, hydrolysis, MgCl,
hydrogen generation, fuel cell, direct water fuel cell, DWFC
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* DWFC (direct water fuel
cell)
Autonomously operates with ony air supplied
* Hydrogeneration Cassette
Hydrogen amount is controllable
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