JPH10203801A - Hydrogen generator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the downsizing of a desulphurization mechanism and the reduction of installation cost by placing a layer of an absorbing agent for removing an S-component contained in a raw material gas, at the upstream side of a layer of a reforming catalyst in a reformer tube. SOLUTION: A layer 21 of an absorbing agent (e.g. a layer of pellet-formed ZnO), which removes an S-component (e.g. mercaptan, etc.), an odorant, contained in a hydrocarbon gas (e.g. CH4 ) of a raw material gas, is placed at the upstream side of a layer 22 of a reforming catalyst (e.g. ruthenium catalyst layer) in a reformer tube 20. It is preferable that a preheating section 16 for preheating the raw material gas with exhaust heat from a burner 28, which heats the reformer tube 20, is placed, and the apparatus is constructed so that the layer 21 of absorbing agent is kept at the activating temperature with the heat which is given to the layer 21 of absorbing agent when the preheated raw material gas passes the layer 21 of absorbing agent and with the heat transmission from a casing 14. It is not necessary to separately place a heating mechanism for the layer 21 of absorbing agent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydrogen generator, and more specifically, to a method in which a raw material gas containing hydrocarbon gas and water vapor passes through a reforming catalyst layer in a reformer tube maintained at a high temperature. The present invention relates to a hydrogen generator that converts hydrogen gas and carbon monoxide at least to produce hydrogen gas by removing the obtained carbon monoxide.

[0002]

2. Description of the Related Art Conventionally, in this type of hydrogen generator, an expensive catalyst substance (such as ruthenium or nickel) of a reforming catalyst layer is poisoned by a sulfur component of an odorant contained in hydrocarbon gas. Losing the reforming function within a relatively short time,
A desulfurization mechanism for desulfurizing the hydrocarbon gas as much as possible in the process before the hydrocarbon gas reaches the reformer tube is provided separately from the reformer tube for the purpose of preventing the gas from being lowered. Was. This is because conventional hydrogen generators are large and have a large production scale, and are designed on the premise that the purity of the produced hydrogen is high. When the operation is started, continuous operation is required without interruption for about 5 years. During this continuous operation, the reforming catalyst layer in the reformer tube cannot be replaced with a new one. In order to maintain the reforming function of
Desulfurize hydrocarbon gas with very high accuracy (in this case,
After converting the sulfur component to hydrogen sulfide, it was adsorbed on zinc oxide).

[0003]

Therefore, in the conventional hydrogen generator, the desulfurization mechanism is inevitably large and its dimensions are large, and a material for desulfurization, for example, zinc oxide (ZnO) is converted to hydrogen sulfide. It was necessary to install a heating mechanism for heating and holding at an activation temperature at which adsorption is easy, that is, 250 to 400 ° C., as a single independent device. An object of the present invention is to provide a desulfurization material that requires a small-scale desulfurization mechanism, has a relatively small size, is relatively inexpensive to install, and has a low desulfurization efficiency. It is an object of the present invention to provide a hydrogen generator which does not require a separate and independent heating mechanism for heating and maintaining the hydrogen at the activation temperature.

[0004]

Means for Solving the Problems In order to achieve the above object, a feature of the hydrogen generator according to the invention described in claim 1 of the present specification is to remove a sulfur component contained in a raw material gas. Adsorbent layer 21 for reformer tube 20
In the upstream of the reforming catalyst layer 22.

[0005] In the description of the above-mentioned features, reference numerals are used to facilitate comparison with the drawings, but the present invention is not limited to the configuration shown in the attached drawings.

[Effects of the Invention] Due to the above-mentioned features,
In the hydrogen generator according to the present invention, the adsorbent is charged into the space near the upper end of the reformer tube, and this can be used as an adsorbent layer for removing a sulfur component contained in the raw material gas. The former tube is inserted into a container made of a fire-resistant partition wall for the purpose of heating the reforming catalyst loaded in the part except the upper and lower ends of the inner part to about 750 ° C. from the outside of the casing of the reformer tube itself. Because it is, the casing of the reformer tube itself,
Heat transfer from the adjacent hot reforming catalyst layer and the refractory barrier surrounding the reformer tube is simply utilized as part of the thermal energy to preheat the adsorbent to its activation temperature. A unique effect of being able to do so.

[0007] In addition to the above-mentioned features, the adsorbent layer may be made of Zn as described in claim 2 of the present specification.
If a preheating mechanism configured to preheat the source gas by exhaust heat of a burner that heats the reformer tube is provided by using O, the adsorbent layer is heated by the preheated source gas. The adsorbent layer made of ZnO is formed by supplementing the heat energy that is insufficient only by the heat transfer from the casing of the reformer tube itself, the adjacent high-temperature reforming catalyst layer, and the refractory partition surrounding the reformer tube. Heating and holding at the activation temperature of 250 to 400 ° C. becomes easy, which is convenient.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. [Schematic Structure of Hydrogen Generator] The hydrogen generator shown in FIG. 1 mainly includes a reformer 100, a CO / CO ₂ converter 200, and a PSA device 300. The reformer 100 mainly converts the natural gas and steam as the raw material gas into a mixture of H ₂ and CO, and the CO / CO ₂ converter 200 converts the CO gas into CO 2.
_The PSA device is used to adsorb CO ₂ gas and water vapor. here,
The structure of the reformer 100 used in the present invention will be described. The reformer 100 includes the reformer tube 20
And a preheating unit 16. Reformer tube 20
Is a closed cylinder made of cast steel having an inner diameter of about 140 mmφ and extending vertically in the vertical direction. The casing 14 is made of refractory fiber and has a cylindrical shape having an inner diameter of about 800 mmφ and extending vertically. An opening 19 is provided at the upper end of the casing 14, and a lower portion of the reformer tube 20 is provided with the opening 19.
And is installed in the casing 14 via the. The inside of the reformer tube 20 is filled with a pellet-shaped ruthenium catalyst except for a void portion 24 provided at the lowermost portion, and has a ruthenium catalyst layer 22 (reforming catalyst) having a height of about 1.5 m. An example of a layer is formed, and a pellet-like ZnO is filled on the ruthenium catalyst layer 22 to form an adsorbent layer 21 having a height of about 0.4 m. Adsorbent layer 21
Has a height substantially equal to the height of the inner wall surface of the casing 14 at the opening 19.

The casing 14 is provided with a through hole 26 extending substantially horizontally from the outside to the inside, and a gas burner 28 is provided on the outer wall surface of the casing 14.
The reformer tube 20 inside the casing 14 is heated from the outside through the through hole 26.
The ruthenium catalyst layer 22 in the reformer tube 20
Based on the detection result of the thermocouple 30 provided in the casing 14, the gas burner 28 heats and maintains the temperature at a constant temperature. The residual heat and exhaust gas provided by the gas burner 28 pass through the exhaust port 17 and reach the inside of the preheating unit 16, and after heating the raw material gas introduction pipe 9 in the preheating unit 16, the heat is supplied from the upper end of the preheating unit 16 to the outside. Be released. The raw material gas preheated by the preheating section 16 first passes through the adsorbent layer 21 and then reaches the ruthenium catalyst layer 22. As the structure of the preheating unit 16, a shell-and-tube heat exchanger or the like can be used.

[Hydrogen Gas Generation Process] Here, a process of generating hydrogen gas by the hydrogen gas generation device according to the present invention will be described with reference to FIG.

(1) Raw Gas Adjustment Step First, natural gas is supplied to the compressor 4. In compressor 4, natural gas is converted to a gauge pressure of about 8
Kg / cm ² (This is the absolute pressure obtained by adding the atmospheric pressure.
After being compressed to about 9 kg / cm ² (the temperature of the natural gas coming out of the compressor 4 is about 50 ° C.), it is sent to the raw material gas supply pipe 8. The raw material gas supply pipe 8 is connected to the water vapor supply pipe 6, so that the raw material gas composed of natural gas and water vapor is supplied to the preheating section 16 of the reformer 100 in the next step. The water / steam ratio is about 1/3.

(2) Reforming Step The raw material gas supplied from the raw material gas supply pipe 8 is supplied to the preheating unit 1.
6 reaches the source gas supply pipe 9 where the gas burner 28
After being preheated by the exhaust gas, etc., and once exiting the preheating section 16 through the conduit, it is introduced into the hollow portion 23 formed at the upper end of the reformer tube 20 via the raw material gas supply pipe 10, and then ZnO is first introduced therefrom. Adsorbent layer 21 composed of
At this time, the sulfur component contained in the odorant (for example, mercaptan) added to the natural gas is adsorbed by the adsorbent layer 21. In the adsorbent layer 21, the heat transmitted from the casing 14 whose inside is kept at a high temperature and the mixed gas heated by the preheating unit 16 move the adsorbent layer 21 downward so that the sulfur component is efficiently adsorbed. It is configured to be kept at the activation temperature of ZnO (about 250 to 400 ° C.) by the heat given to the adsorbent layer 21 when passing. Next, the raw material gas that has passed through the adsorbent layer 21 passes downward through the inside of the ruthenium catalyst layer 22 heated to about 750 ° C. by the gas burner 28. When passing through the ruthenium catalyst layer 22, the raw material gas composed of natural gas and water vapor is reformed into hydrogen gas and carbon monoxide based on the reaction formula of CH ₄ + H ₂ 0 = 3H ₂ + CO. The resulting mixture of the hydrogen gas and the carbon monoxide after the reforming is once filled in the void 2 provided in the lowermost portion of the reformer tube 20.
After exiting to 4, the central part of the reformer tube 20 moves upward through the vertically extending discharge pipe 12 and is mixed with the mixture before reforming from the reformer tube 20 and the reformer 100 through the conduit 34 without mixing. It is discharged (discharge temperature is about 600 ° C.). Here, the adsorbent layer 21 made of ZnO provided upstream of the ruthenium catalyst layer 22.
Is a simple means for suppressing the sulfur component contained in the odorant added to the natural gas from poisoning the ruthenium catalyst layer 22, and adsorbs the sulfur component as it is without converting it to hydrogen sulfide. The structure is simple because it is intended. Since the adsorbent layer 21 is provided, the ruthenium catalyst layer 22 can be used continuously for about one year. Similarly, the adsorbent layer 21 made of ZnO can be used continuously for about one year. Therefore, the hydrogen generator may be stopped approximately every year, and the adsorbent layer 21 and the ruthenium catalyst layer 22 in the reformer tube 20 may be simultaneously replaced with fresh ones. In this embodiment, the height of the ruthenium catalyst layer 22 in the reformer tube 20 is set to about 1.5.
The reason why the height of the adsorbent layer 21 made of m and ZnO is set to about 0.4 m is that the ruthenium catalyst layer 22 is poisoned by sulfur of about 0.1% of its own weight and becomes unusable, and ZnO becomes unusable. It is based on the experimental fact that about 30% of its own weight of sulfur can be adsorbed.

(3) CO Conversion Step The obtained mixture of the reformed hydrogen gas and carbon monoxide is supplied to the CO / CO ₂ converter 200 through the conduit 34. In the CO / CO ₂ converter 200, after the supplied mixture is cooled to about 300 ° C., carbon monoxide in the mixture is converted into carbon dioxide based on the reaction formula CO + H ₂ 0 → CO ₂ + H ₂ . As a catalyst for CO / CO ₂ conversion, an iron-chromium-based catalyst can be used. Where C
O / CO ₂ conversion after cooling the mixture to about 190 ° C., copper - may be used zinc-based catalyst. A mixture of hydrogen gas and carbon dioxide discharged from the CO / CO ₂ converter 200 passes through a gas cooler 37 and is then supplied from a conduit 38 to a chamber tank 40. In the chamber tank 40, the water condensed by the gas cooler 37 is removed. The mixture of hydrogen gas and carbon dioxide from which water has been removed is supplied from the chamber tank 40 through the conduit 42 to the PSA device 3.
Sent to 00.

(4) CO ₂ Adsorption Step The PSA device (pressure swing adsorption) 300 is composed of three gas adsorption towers 46, 46 ′, 46 ″. 46 '' is filled with a gas adsorbing substance such as activated carbon. The mixture of the hydrogen gas and carbon dioxide is supplied to the gas adsorption towers 46, 46 ', 4
When passing through 6 ″, mainly only carbon dioxide is selectively adsorbed, and as a result, hydrogen gas is separated and extracted.
The hydrogen gas thus separated and extracted is used as a product in conduit 4
The collected hydrogen gas is collected at the product hydrogen gas outlet 50 through 8.

(5) Offgas Return Step The component gas other than the hydrogen gas generated by the PSA device 300, that is, carbon dioxide gas as an offgas and trace amounts of carbon monoxide and methane gas are exhausted from the conduit 70.

[Alternative Embodiment] <1> As in the above embodiment, the preheating section 16 is not provided separately from the casing 14 or the reformer tube 20. Instead, as shown in FIG. May enter the casing 14 so that the majority of the adsorbent layer 21 is at the activation temperature. The adsorbent layer 2
By adjusting the depth of entry into a high-temperature portion (that is, from the wall surface of the casing 14) of the first adsorbent layer 1, most of the adsorbent layer 21 can be brought to its activation temperature. May be provided, and the height of the reformer tube 20 with respect to the casing 14 may be adjusted in accordance with the detection result of the temperature measuring means.

<2> The gas used together with steam as a raw material is not limited to natural gas, and any hydrocarbon gas to which a sulfur component is added is within the scope of the present invention.

<3> A hydrogen gas generator using a nickel catalyst layer instead of the ruthenium catalyst layer 22 is also within the scope of the present invention.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a hydrogen gas generator according to the present invention.

FIG. 2 is a schematic view of another embodiment of the hydrogen gas generator of FIG.

[Explanation of symbols]

Reference Signs List 6 steam supply pipe 8, 9, 10 source gas supply pipe 20 reformer tube 21 adsorbent layer 22 reforming catalyst layer 28 gas burner 100 reformer 200 CO / CO ₂ converter 300 PSA device

Claims (2)

[Claims] 1. A raw material gas containing a hydrocarbon gas and water vapor is passed through a reforming catalyst layer in a reformer tube kept at a high temperature, and these are converted into hydrogen gas and carbon monoxide. A hydrogen generator for producing hydrogen gas by removing carbon monoxide, wherein an adsorbent layer for removing a sulfur component contained in the raw material gas is provided as the reforming catalyst layer in the reformer tube. Hydrogen generator installed on the upstream side of 2. The hydrogen generator according to claim 1, wherein the adsorbent layer is made of ZnO, and further comprising a preheating mechanism for preheating the raw material gas by exhaust heat of a burner for heating the reformer tube. .