Apparatus for producing hydrogen

Gas: heating and illuminating – Apparatus for converting or treating hydrocarbon gas

Reexamination Certificate

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C422S198000, C422S198000

Reexamination Certificate

active

06802876

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus for producing hydrogen by a steam reforming reaction using a hydrocarbon or an oxygen-containing hydrocarbon as a raw material.
2. Description of the Related Art
A conventional apparatus for producing hydrogen with the use of a hydrogen separation type reformer is proposed, for example, in Japanese Unexamined Patent Publication No. 4-325402. Disclosed in this proposal is an apparatus for producing hydrogen for a fuel cell with the use of a hydrogen separation type reformer from which hydrogen is withdrawn by a pressure reducing means. The concept of constitution of this apparatus is illustrated in FIG.
9
.
As shown in
FIG. 9
, a hydrogen separation membrane
02
and a catalyst
08
are provided in a hydrogen separation type reformer
01
. A gas as a raw material (hereinafter referred to as a raw material gas)
06
and steam
07
are fed to the hydrogen separation type reformer
01
, where a reforming reaction takes place. Hydrogen formed by the reforming reaction is separated by the separation membrane
02
. On a hydrogen permeation side
03
where the separated hydrogen permeates, a pressure reducing device
04
is provided to recover high purity hydrogen
05
.
With the hydrogen separation type reformer
01
, the raw material gas
06
comprising a hydrocarbon or an oxygen-containing hydrocarbon such as methane or methanol is introduced, and reformed on the catalyst
08
by a steam reforming reaction and a CO shift reaction to form hydrogen and carbon dioxide mainly. The hydrogen is selectively separated, for recovery, by the hydrogen separation membrane
02
built into the catalyst
08
. As the hydrogen separation membrane
02
, a non-porous thin film with a thickness as small as about several to 50 &mgr;m, which comprises a hydrogen-permeable metal film of Pd or Pd alloy, is used, as shown in Japanese Unexamined Patent Publication No. 6-321503. As the catalyst
08
, a catalyst containing a group VIII metal (Fe, Co, Ni, Ru, Rh, Pd or Pt) is preferred, and a catalyst bearing Ni, Ru or Rh or an Nio-containing catalyst is particularly preferred.
A perspective sectional view of the structure of a typical hydrogen separation type reformer is shown in
FIG. 7
, and a cross sectional view of the structure is shown in FIG.
8
. As shown in these drawings, a hydrogen separation type reformer
10
has an outer cylinder
14
with a closed bottom
12
, and an intermediate cylinder
16
and an inner cylinder
18
disposed in this order inwardly of the outer cylinder
14
. The outer cylinder
14
, the intermediate cylinder
16
, and the inner cylinder
18
are formed upright. At an upper part of a second annular space portion
26
between the intermediate cylinder
16
and the inner cylinder
18
, a preliminary reforming portion
25
is provided. Below the preliminary reforming portion
25
, a plurality of hydrogen permeable pipes
34
having a metal film selectively permeable to hydrogen are disposed concentrically with the second annular space portion
26
.
A burner
46
burns a fuel gas, which has been introduced through a fuel gas pipe
48
, with air taken in through an air intake pipe
50
to supply thermal energy necessary for a steam reforming reaction to the second annular space portion
26
filled with a reforming catalyst A, thereby keeping the catalyst at a predetermined temperature. The fuel gas passes through an inner tube hollow portion
22
, a space between the bottom
12
of the outer cylinder
14
and an annular bottom portion
24
, and a first annular space portion
20
, and goes outside through a combustion gas outlet
52
. During this motion, the fuel gas heats a layer of the catalyst filled into the second annular space portion
26
.
A process feed gas comprising a gas mixture of steam and a raw material gas composed of a hydrocarbon or an oxygen-containing hydrocarbon, such as methane or methanol, is introduced through a feed gas inlet
54
provided at an upper part of the second annular space portion
26
. The process feed gas is partially converted into hydrogen at the preliminary reforming portion
25
, and flowed into the layer of the catalyst filled into the second annular space portion
26
, whereby the process feed gas is converted into hydrogen at a high temperature. The resulting hydrogen is selectively separated and collected by the hydrogen permeable pipes
34
, passed through a third space portion
33
and flowed out through a hydrogen outlet
56
provided above the third space portion
33
. The unreacted raw material gas and the resulting CO and CO
2
gases, which have passed through the catalyst layer, flow through an off-gas pipe
60
having an opening at a lower part of the second annular space portion
26
, and flow out of the system through an off-gas outlet
62
.
With the foregoing conventional apparatus, the resulting hydrogen is withdrawn from the hydrogen separation type reformer
10
by a pressure reducing device. As is well known, a hydrogen separation membrane gives a necessary amount of hydrogen with high efficiency, accordingly, with a small membrane area, if the pressure of the hydrogen permeation side is minimized. Thus, a highly efficient pressure reducing device has been required. A vacuum pump or the like is conceivable as a pressure reducing device. However, such a rotary device has difficulty in efficiently delivering a light gas, such as hydrogen, thus requiring a high power. Furthermore, the aforementioned Japanese Unexamined Patent Publication No. 4-325402 does not propose a concrete apparatus layout including a pressure reducing device, and cannot actualize a feasible apparatus.
SUMMARY OF THE INVENTION
The present invention has been accomplished in light of these circumstances. It is an object of this invention to actualize such a concrete and feasible apparatus layout involving a pressure reducing device and provide an apparatus for producing hydrogen with the use a hydrogen separation type reformer, the apparatus having a minimal area required, and having improved durability while using a pressure reducing device.
A first aspect of the present invention, as a means of attaining the above object, is an apparatus for producing hydrogen by a steam reforming reaction, on a catalyst, of a hydrocarbon or an oxygen-containing hydrocarbon as a raw material, the apparatus comprising a hydrogen separation type reformer which has a means for heating the catalyst and which has a hydrogen separation membrane built into a layer of the catalyst for selectively separating hydrogen, a cooling means for cooling high temperature high purity hydrogen obtained from the reformer, and a hydrogen charge/discharge means disposed downstream from the cooling means and composed of a hydrogen storage material.
According to the first aspect of the invention, the following actions and effects are exhibited:
The high temperature high purity hydrogen that has been separated from the reformer is once cooled by the cooler, the indirect heat exchanger, to a temperature at which hydrogen is easily charged into the hydrogen storage material. Then, the cooled hydrogen is fed to the hydrogen storage material. As a result, the hydrogen charging rate and the amount of hydrogen charged are increased, and hydrogen can be withdrawn from the reformer at a lower pressure than the atmospheric pressure. Thus, the membrane area of the hydrogen separation can be decreased. Moreover, a required power can be decreased markedly in comparison with the power required for the use of a vacuum pump.
When hydrogen charged in the hydrogen storage material is to be delivered, the temperature of the hydrogen storage material is set at an appropriate level, whereby high pressure hydrogen can be obtained. Thus, a hydrogen compression power necessary when a compressor is used can be cut down markedly.
A second aspect of the invention is the apparatus for producing hydrogen as the first aspect of the invention, wherein the cooling means for cooling the high temperature high purity hydrogen co

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