JP4571831B2 - LPG desulfurization system and desulfurization method - Google Patents

Description

  The present invention relates to a desulfurization system and a desulfurization method for sulfur compounds from LPG as a hydrogen supply source for a polymer electrolyte fuel cell or the like.

The polymer electrolyte fuel cell (PEFC) is expected to be applied as a power source in a wide range of fields such as automobile power sources and distributed power sources because of its low pollution and higher thermal efficiency. As a hydrogen production method, hydrogen is generally produced by a steam reforming reaction or the like using a catalyst such as city gas in a reformer. However, since the steam reforming catalyst is poisoned by the sulfur compound contained in the fuel, it is necessary to remove the sulfur content by a desulfurizing agent as a pretreatment.
City gas contains sulfur compounds such as tertiary butyl mercaptan and dimethyl sulfide as odorants, and a certain concentration of sulfur compounds of several ppm is uniformly discharged. In this case, examples of the desulfurizing agent include a room temperature desulfurizing agent, a heat desulfurizing agent, and a hydrogenated desulfurizing agent, and examples of the desulfurizing agent that can be easily handled include a room temperature desulfurizing agent and can be easily used.

On the other hand, propane gas (LPG) is also a promising fuel for PEFC and can be converted to hydrogen by a steam reforming catalyst. LPG is widely used in areas where city gas infrastructure is not deployed, and is a nationwide fuel. This LPG also contains a variety of sulfur compounds as odorants, and sulfur compounds poison the reforming catalyst for fuel cells, so desulfurization is required to apply LPG to fuel cells. .
Conventional LPG has hardly been desulfurized when used for consumer use. For fuel cells, desulfurization in city gas is mainly performed at room temperature, but desulfurization when using LPG is mainly performed by heating reaction or hydrogenation reaction system. These desulfurization methods are not convenient and stable and are not suitable for household fuel cell systems. In the room temperature adsorption method, a zeolitic adsorbent is typical, and is generally used as a desulfurization method in city gas.

However, in the case of LPG, the following points are different from city gas regarding the desulfurization method.
First, LPG contains various sulfur compounds and varies in concentration range depending on the production area and manufacturing method. A room-temperature adsorbent developed as an adsorbent in city gas can be applied to LPG, but LPG contains a wide variety of sulfur. Therefore, since the kind of sulfur compound and its sulfur concentration are changed, the adsorption characteristics of the adsorbent are changed, and sufficient room temperature adsorption performance cannot be exhibited.

  Secondly, the sulfur compounds are concentrated at the bottom of the LPG cylinder as they are used, and when the gas residue is reduced, high-concentration sulfur compounds are discharged and the sulfur concentration fluctuates. In the LPG cylinder, the concentration of S is hardly changed from the initial stage to 70% consumption, but high concentration of S is discharged after 90% consumption. This is because the sulfur content in LPG is mainly emitted from the light gas, whereas the sulfur content is heavier than LPG (mainly propane), so it is mainly concentrated in the liquid phase of LPG. Has been. Therefore, it is considered that the sulfur content dissolved in the liquid layer is discharged as high concentration S as the residual LPG becomes small. LPG contains sulfur compounds such as dimethyl sulfide, tertiary butyl mercaptan, and ethyl mercaptan, but when LPG is supplied from a cylinder, the sulfur concentration changes greatly over time. For this reason, since the adsorption | suction characteristic of the said normal temperature adsorbent changes by sulfur concentration changing, sufficient adsorption | suction performance was not obtained and it was not able to respond to the sulfur concentration change of a cylinder.

Third, some sulfur compounds contain carbonyl sulfide (COS), which is difficult to remove with a room temperature desulfurization agent. This COS could not be sufficiently adsorbed and removed by a room temperature adsorbent, and desulfurization treatment was difficult for LPG containing COS. Therefore, establishment of a desulfurization method suitable for LPG has been expected.

In view of the above problems, the present inventors are able to perform stable desulfurization in response to changes in sulfur concentration over time from a cylinder when adopting an adsorption method for sulfur removal in LPG, and mainly adsorb In order to develop an efficient desulfurization method in LPG based on the desulfurization by LNG, we have intensively studied. And as a desulfurization method suitable for LPG, the type of desulfurization agent that can solve the above first to third problems and its application method were also examined.
As a result, the present inventors have found that the above problem can be solved by constructing a system based on a new combination of a desulfurizing agent and an LPG cylinder. In addition, it was found that LPG contained in COS can be a simple and efficient desulfurization method by combining not only the room temperature adsorption method but also the heat adsorption method.
The present invention has been completed from such a viewpoint.

  That is, the first system of the present invention is an LPG desulfurization system in which a flow path of gas flowing from an LPG cylinder is branched and two or more desulfurization agents are installed in parallel, and at least one desulfurization agent is provided. The present invention provides a desulfurization system for LPG, which is a desulfurization agent for low sulfur concentration, and at least one other desulfurization agent is a desulfurization agent for high sulfur concentration. Here, the amount of the metal component supported on the high sulfur concentration desulfurizing agent is preferably larger than the amount of the metal component supported on the low sulfur concentration desulfurizing agent. The desulfurization agent for low sulfur concentration and the desulfurization agent for high sulfur concentration are those which carry beta type zeolite, X type zeolite, Y type zeolite or MFI type zeolite as a carrier and silver, copper or cobalt as a metal component. Is preferred. In these desulfurization agents, since sulfur compounds in ordinary LPG can be adsorbed and removed at normal temperature, it can be dealt with by filling the adsorbent in an amount corresponding to the required replacement time.

  The desulfurization system may further include a switching unit that switches a gas flow path leading to the two or more desulfurization agents, together with a detection unit that detects a remaining gas amount in the LPG cylinder. As a result, since the sulfur concentration in the LPG cylinder depends on the LP residual amount, the LP residual amount is monitored by a detecting means such as a liquid level meter installed in the cylinder or a weight meter that measures the residual weight of the cylinder itself. Switch the desulfurization agent used. As the detection means, in addition to the liquid level meter, for example, a colorant capable of judging the sulfur adsorption state of the desulfurizing agent is used. Can do. Furthermore, a method of adding a colorant to the desulfurizing agent and monitoring the usable level and the period of the desulfurizing agent is one of the detection means.

  The first method of the present invention is a method of performing desulfurization by providing at least two or more desulfurization agents in parallel in a gas flow path flowing from an LPG cylinder, and is low at a stage where the gas consumption rate in the cylinder is low. A low-concentration gas desulfurization process that allows the LPG cylinder gas to pass through the desulfurization agent for sulfur concentration, and a high-concentration gas that allows the LPG cylinder gas to pass through the desulfurization agent for high sulfur concentration when the gas consumption rate increases as the gas is used And a desulfurization step. The present invention provides a desulfurization method for LPG. Here, the low sulfur concentration usually means a concentration of less than 1 ppm, and the high sulfur concentration usually means a concentration of 1 ppm or more. In this desulfurization method, in addition, the remaining amount of gas in the cylinder consumed by gas circulation is detected, and when a desired consumption rate (for example, 70%, 80% or 90%) is reached, a detection signal is output. A detection step of sending, and a desulfurization agent switching step of switching the desulfurization agent to be passed from the desulfurization agent for low sulfur concentration to the desulfurization agent for high sulfur concentration by the detection signal.

The second system of the present invention is an LPG desulfurization system in which two or more desulfurization agents are installed in series in a gas flow path flowing from an LPG cylinder, and is located on the upstream side with respect to the gas flow direction. A room temperature desulfurization agent is disposed, and a heat desulfurization agent is disposed on the downstream side thereof. The heat desulfurization agent is disposed inside the reformer for the fuel cell , and desulfurization of LPG heated by the heat energy inside the reformer. A system is provided. In this case, the heating desulfurizing agent is not heated outside the heater, but is filled inside the reformer and heated by burner heating or reaction heat of the catalyst. The room-temperature desulfurizing agent is preferably one in which beta-type zeolite, X-type zeolite, Y-type zeolite or MFI-type zeolite is supported as a carrier and silver, copper or cobalt is supported as a metal component. The heat desulfurizing agent is preferably a metal of Ni, Cu, Zn, or Fe or an oxide thereof .

A second method of the present invention is a method of performing desulfurization by providing at least two or more desulfurization agents in series in a gas flow path flowing from an LPG cylinder, on the upstream side with respect to the gas flow direction. A desulfurization treatment is usually performed in the range of 0 to 50 ° C. using a room temperature desulfurization agent, and a heat desulfurization agent is usually used at a downstream side of the first desulfurization step and a temperature of 70 to 500 ° C. Preferably, the desulfurization treatment is performed in the range of 100 to 400 ° C., more preferably 150 to 300 ° C. In the case where two or more LPG cylinders are installed in parallel, it is further added to the above step. Detecting the remaining amount of gas in the at least one LPG cylinder consumed by gas distribution and sending a detection signal when a desired consumption rate (for example, 70%, 80% or 90%) is reached. LPG remains in the LPG cylinder due to the process and the detection signal. In to that state, there is provided a LPG desulfurization method including switching at least one other LPG cylinder supply gas, a cylinder switching step. In LPG containing COS, a room-temperature desulfurizing agent is disposed in the former stage and a heating desulfurizing agent is disposed in the latter stage to completely remove the sulfur content in the LPG. The heat desulfurizing agent is kept at a temperature of 70 ° C. or higher and is fixed as a metal sulfide. In this method, even if the room temperature desulfurizing agent is periodically replaced, the heated desulfurizing agent can be used without replacement.
By installing two or more cylinders in parallel and switching to a new cylinder in the cylinder switching step, the gas supplied to the desulfurization agent can be kept at a sulfur concentration below a certain concentration. In the third method, after the cylinder switching process, a process of filling the cylinders consumed by gas circulation with other LPGs with the remaining LPG as it is can be introduced.

In the present invention, the following configuration can be adopted as the third system by arbitrarily combining with the first system or the second system. That is, a plurality of LPG cylinders of the first system or the second system can be installed in parallel. In this third system, two or more LPG cylinders are installed in parallel, each LPG cylinder is provided with detection means for detecting the remaining amount of gas, and the supply gas leading to the desulfurizing agent is supplied to the LPG cylinder. Switching means for switching between two or more LPG cylinders is provided.
As the detection means, it is possible to use the same method as in the first system, and it is also possible to use a colorant capable of determining the sulfur adsorption state of the desulfurizing agent, for example, in addition to the liquid level meter.

  In the present invention, the sulfur compound in the LPG cylinder contains at least one selected from the group consisting of dimethyl sulfide, methyl ethyl sulfide, and tertiary butyl mercaptan.

  According to such a desulfurization system and desulfurization method of the present invention, when an adsorption method is adopted for removing sulfur in LPG, stable desulfurization is possible in response to a change in sulfur concentration with time from a cylinder. In addition, an efficient fuel cell operation method using LPG having high convenience can be provided.

  Hereinafter, the present invention will be described in detail based on embodiments with reference to the accompanying drawings.

Embodiment (Part 1)
FIG. 1 schematically shows an example of the system configuration of the LPG desulfurization method according to the present embodiment. Sulfur compounds in LPG are targeted for cases where dimethyl sulfide, methyl ethyl sulfide, tertiary butyl mercaptan, etc. are included (LPG1).

First, the configuration of the system in FIG. 1 will be described.
The cylinder 2 filled with LPG is provided with a liquid level meter 3 as one of detecting means, and an open / close valve 6 is provided at a gas outlet connected to the supply line 4. The LPG supply line 4 is branched before the room temperature desulfurizing agent 1, one of which leads to the room temperature desulfurizing agent 1A via the switching valve 7A, and the other which leads to the room temperature desulfurizing agent 1B via the switching valve 7B. ing. In the downstream of the room temperature desulfurization agents 1A and 1B, after the valves are provided, the lines merge into one. The desulfurized gas line is connected to a reformer of the fuel cell system. In the middle of the line, it may be connected to the analyzer 5 so that a part of the gas can be collected and analyzed. In addition, about each valve, such as a switching valve, it is also possible to fully comprise a system using other valves, such as a three-way valve, and it is not limited to said form at all.

Next, the operation when the system shown in FIG. 1 is used will be specifically described.
LPG discharged from the cylinder 2 is sent from the opened on-off valve 6 to the room temperature desulfurization agent 1 through the supply line 4. At the beginning of use of the cylinder 2, the switching valve 7A is opened, the switching valve 7B is closed, and LPG is sent to the room temperature desulfurization agent 1A which is a desulfurization agent for low sulfur concentration. The desulfurized gas is sent to the subsequent stage, and if necessary, a part thereof can be sent to the analyzer 5 to monitor the desulfurization rate.
Since the sulfur concentration in the LPG cylinder 2 depends on the LP residual amount, the LP residual amount is monitored by the liquid level meter 3 and the switching operation of the room temperature desulfurizing agent to be used is performed. As described above, there is a liquid level in the cylinder 2, and when the consumption of LP increases, the liquid level falls to the bottom of the cylinder. The liquid level meter 3 is detection means for sending a detection signal when the position of the liquid level is lower than a certain position in the cylinder 2. The detection means is connected to the switching valves 7A and 7B, closes the switching valve 7A that was opened when the cylinder 2 was first used by the detection signal, and opens the switching valve 7B. As a result, the LPG that has been sent to the room temperature desulfurization agent 1A that is a low sulfur concentration desulfurization agent is sent to the room temperature desulfurization agent 1B that is a high sulfur concentration desulfurization agent.

  In addition, as a detection means which can be used by this invention, the coloring agent provided in the supply line 4 other than the liquid level meter 3 shown in FIG. The sulfur concentration in the gas flowing through the supply line 4 increases rapidly after the cylinder 2 has consumed more than a certain amount. Therefore, the color of the colorant does not change at a certain sulfur concentration from the beginning of use of the cylinder, but the color changes at a stroke due to a sudden increase in the sulfur concentration. The color change of the colorant can be identified as detection means, and a detection signal can be sent. For example, a colorant that becomes black in a sulfur adsorption state is easy to detect with visible light. Since the discolored colorant is difficult to reuse, it is usually preferable to replace the entire colorant in the form of a filter or the like.

In the desulfurization method for LPG 1 shown in the present embodiment, the gas in the LPG 1 cylinder 2A can be used to the end, and a desulfurization agent for low sulfur concentration and a desulfurization agent for high sulfur concentration are used. Install two or more in parallel.
As the room-temperature desulfurization agent 1, for example, a beta zeolite, an X zeolite, a Y zeolite or an MFI zeolite supported as a carrier and a metal component supporting Ag, Cu or Co can be used. Specifically, Ag ion-exchanged zeolite, Cu ion-exchanged zeolite, Co ion-exchanged zeolite or the like obtained by ion-exchange of Ag, Cu, or Co to zeolite such as Na-type zeolite is preferable.

  In the present embodiment, it is preferable that the room temperature desulfurization agent 1B, which is a desulfurization agent for high sulfur concentration, carries more metal components Ag, Cu, or Co than the room temperature desulfurization agent 1A, which is a desulfurization agent for low sulfur concentration. For example, room temperature desulfurization agent 1A is usually used with a metal component of 0.3 to 5.0% by weight, preferably 0.5 to 3.0% by weight, but room temperature desulfurization agent 1B completely removes S even at high concentrations of S. In order to achieve this, it is preferable to use a material carrying about 7 to 25% by weight, preferably about 10 to 20% by weight of Ag.

Embodiment (2)
FIG. 3 shows another example of the system configuration of the LPG desulfurization method according to the present embodiment. In the present embodiment, the sulfur compound in LPG is mainly targeted when carbonyl sulfide (COS) or the like (LPG2) is contained in addition to dimethyl sulfide, methyl ethyl sulfide, tertiary butyl mercaptan, and the like.

First, the configuration of the system of FIG. 3 will be described.
The cylinder 2 filled with LPG2 containing COS is provided with an on-off valve 6 at the gas outlet connected to the supply line 4. The LPG supply line 4 leads to the room temperature desulfurization agent 1. A heated desulfurizing agent 9 is installed in the downstream of the room temperature desulfurizing agent 1 through a line 12. A heater 8 is provided in the vicinity of the heating desulfurizing agent 9, and the desulfurizing agent 9 can be kept warm to a desired temperature. The sulfur concentration analyzer 5 is connected to a gas line 12 via a valve 10 or 11, respectively, so that the S concentration of both the downstream of the room temperature desulfurizing agent 1 and the downstream of the heated desulfurizing agent 9 can be monitored.

Next, the operation when the system shown in FIG. 3 is used will be specifically described.
LPG discharged from the cylinder 2 is sent from the opened on-off valve 6 to the room temperature desulfurization agent 1 through the supply line 4. When LPG 2 is used as a fuel, room temperature desulfurization agent 1 can remove S components other than COS, but COS cannot be removed. Therefore, COS is removed by the downstream heating desulfurization agent 9. In addition, even for the high-concentration S component after 90% consumption of the cylinder 2, various sulfur components that cannot be removed by the room temperature desulfurizing agent 1 and flow downstream are completely removed by the heated desulfurizing agent 9.

In the LPG desulfurization method shown in the present embodiment, the gas in the LPG 2 cylinder 2 can be used to the end, and the normal temperature desulfurization agent 1 is upstream in the gas flow direction and the heat desulfurization is downstream. Two or more agents 9 are used in series.
As room temperature desulfurization agent 1, the thing similar to the said embodiment (the 1) can be used. The heating desulfurizing agent 9 is not particularly limited, but for example, a catalyst in which Ni, Cu, Zn, Fe, Co, etc. are supported on a carrier such as alumina, silica, titania, zirconia, zinc oxide catalyst, Cu- Preferred examples include Zn-based catalysts, Ni-Cu-based catalysts, Ni-Fe-based catalysts, and the like.

  Further, in the present embodiment, as shown in FIG. 5, the heat desulfurizing agent 9 can be combined with the reformer 20 of the fuel cell system and filled into the reformer 20 so that exhaust heat can be used. . According to this aspect, the heater 8 as a heating means becomes unnecessary, and the heat desulfurizing agent 9 can be used stably for a long period without replacement. When using a combination of a room temperature desulfurization agent and a heat desulfurization agent, about 80% or more of the S content is removed with the upstream room temperature desulfurization agent 1, and the final desulfurization is performed with the heat desulfurization agent. For this reason, considering that the installation space for the heated desulfurizing agent 9 is limited and that basically no replacement is required, the S compound other than COS is removed in advance, and the heated desulfurizing agent with as little filling amount as possible. 9 is preferably used.

  When COS is contained in the LPG as in the present embodiment, it is difficult to remove sufficiently with the room temperature desulfurization agent, and therefore, the room temperature desulfurization agent and the heat desulfurization agent are connected in series. In addition, although installation of only a heat desulfurization agent is also considered, since a heat desulfurization agent is a fixed type and is not a replacement | exchange type | mold, since the lifetime of several years or more is required, a large capacity | capacitance desulfurization agent may be needed. Even if a large amount of COS is contained in LPG, it is considered that the total sulfur content is 20% or less. Therefore, the capacity of the heating desulfurization agent installed in the downstream is minimized and the energy loss due to heating is minimized. It is necessary to provide an efficient PEFC system. In order to suppress external heating in the heated adsorbent, it is preferable to circulate LPG by incorporating a desulfurizing agent inside the reformer. As the heat desulfurizing agent, Ni, Cu, ZnO and the like are particularly preferably used as the main component, and it is desirable to remove COS in LPG by the following reaction.

Embodiment (Part 3)
FIG. 6 shows another example of the system configuration of the LPG cylinder that can be used in combination with the mode of the first embodiment (part 1) or (part 2). In FIG. 6, the case where only the room temperature desulfurizing agent 1 is used as the system after the supply line 4 is described, but in order to achieve the object of the present invention, the system as shown in FIG. 9 or 10 is desirable. Here, the sulfur compounds in LPG are mainly targeted when dimethyl sulfide, methyl ethyl sulfide, tertiary butyl mercaptan, etc. are contained (LPG1).

First, the configuration of the system of FIG. 6 will be described.
The cylinders 2A and 2B filled with LPG1 are installed in parallel, and on-off valves 6A and 6B are provided independently at gas outlets connected to the supply line 4, respectively. The cylinders 2A and 2B are respectively provided with liquid level meters 3A and 3B as one of detecting means. The LPG supply line 4 leads to the room temperature desulfurization agent 1. Connected to the downstream of the room temperature desulfurization agent 1 is a gas line 12 that is desulfurized from a part of the line and is connected to the analyzer 5 for the sulfur concentration in the gas. In addition, as a detection means, it is not restricted to a liquid level meter, For example, the aspect which provides a coloring agent in the supply line 4 may be sufficient.

Next, the operation when the system shown in FIG. 6 is used will be specifically described.
At the beginning of use, LPG discharged from the cylinder 2A to be used first is sent to the room temperature desulfurization agent 1 through the supply line 4 from the opened on-off valve 6A. At this time, the on-off valve 6B is closed. The desulfurized gas is sent to the subsequent stage, and if necessary, a part thereof can be sent to the analyzer 5 to monitor the desulfurization rate.
Since the sulfur concentration in the LPG cylinder 2A depends on the LP residual amount, the LP residual amount is monitored by the liquid level meter 3A and the cylinder to be used is switched. When about 80 to 90% of the cylinder 2A in which the concentration of S in LPG is high is consumed by the liquid level meter 3, the liquid level meter in the cylinder detects and sends a detection signal. The detection means is connected to the on-off valves 6A and 6B, and closes 6A that was initially opened by the detection signal and opens 6B. Thus, the gas sent from the cylinder 2A to the supply line 4 is sent from the cylinder 2B, and the supply from the cylinder 2A is completed.

In the parallel arrangement shown in FIG. 6, a constant concentration of S is supplied to the room temperature desulfurization agent 1 substantially uniformly by performing the cylinder switching process based on the detection signal at an appropriate time. Therefore, as shown in FIG. 7, the outlet S concentration can be set to S <0.1 ppm (below the detection limit of the analyzer), and stable desulfurization performance above a certain level can be obtained. Therefore, in the above embodiment (part 1) or (part 2), if the embodiment shown in FIG. 9 or FIG. 10 provided with a plurality of cylinders is adopted, the desulfurization performance of a certain level or more explained in this embodiment. Therefore, desulfurization can be performed more reliably and stably.
Here, the cylinder 2A in which the high-concentration S component remains can be reused by filling LPG without adding the S component (odorant) as it is.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications and changes can be made without departing from the scope of the present invention. is there.
In the following examples, a method for preparing a desulfurizing agent, a performance evaluation result, and a method for desulfurizing LPG will be described in more detail. However, the present invention is not limited to these examples.

Example 1 (Method for preparing desulfurizing agent)
(Preparation of room temperature desulfurization agents I-VI)
Add 50 g of Na-type beta zeolite (SiO ₂ / Al ₂ O ₃ = 20) powder to 5 liters of water and keep it at 60 ° C, then add 34 g of silver nitrate (AgNO ₃ , MW = 170) and stir It was. After ion exchange treatment for 8 hours, washing with water filtration was performed, and drying was performed at 110 ° C. for 12 hours to prepare Ag ion exchange beta zeolite. This sample is designated as room temperature desulfurization agent I.

In the same manner as the above room temperature desulfurization agent I, instead of Na type beta zeolite, Na type X zeolite (SiO ₂ / Al ₂ O ₃ = 3) as room temperature desulfurization agent II and Na type Y zeolite (normal temperature desulfurization agent III) SiO ₂ / Al ₂ O ₃ = 5.6), Na ion MFI zeolite (SiO ₂ / Al ₂ O ₃ = 30) as room temperature desulfurization agent IV, Ag ion exchange is performed in the same way, Ag ion exchange Zeolite, Ag ion exchange Y zeolite, and Ag ion exchange MFI zeolite were prepared. These samples are designated as room temperature desulfurization agents II, III, and IV, respectively.
Moreover, in the same method as the above room temperature desulfurization agent I, instead of silver nitrate, 60 g of copper nitrate (Cu (NO ₃ ) ₂ · 6H ₂ O, MW = 296) as room temperature desulfurization agent V and cobalt nitrate as room temperature desulfurization agent VI Using 58 g of (Co (NO ₃ ) ₂ · 6H ₂ O. Mw = 291), Cu ion exchange beta zeolite and Co ion exchange beta zeolite were prepared by the same method. This sample is designated as room temperature desulfurization agents V and VI.

(Preparation of heat desulfurization agents I to III)
When COS is present in LPG, it is preferable to use the above-mentioned room temperature desulfurization agent and heat desulfurization agent in series. As a heat desulfurizing agent, it was prepared by the following method. Adsorbent (NiO / Al ₂ O ₃ ) obtained by impregnating and supporting 20% by weight of nickel nitrate with Ni to 100% by weight of γ-Al ₂ O ₃ and calcining at 500 ° C for 5 hours Agent I.
Further, ammonia was dropped into an aqueous zinc nitrate solution to obtain a precipitate at pH = 7, and the precipitate was filtered, washed, dried, and calcined at 500 ° C. for 5 hours. This sample (ZnO) is used as a heat desulfurization agent II.
Furthermore, sodium carbonate was added to a mixed aqueous solution of copper nitrate and zinc nitrate (Cu: Zn = 50: 50 atomic ratio) to obtain a composite hydroxide precipitate at pH = 7. The precipitate was washed, filtered, dried and calcined at 300 ° C. for 5 hours. This sample (CuO / ZnO) is used as the heat desulfurization agent III.

[Changes in concentration at the outlet S in LPG 1 and 2]
Table 1 shows the relationship between the amount of residual LPG in the cylinder and the concentration at the outlet S using LPG 1 and 2. LPG1 does not contain COS, and LPG2 contains COS. A typical average S compound concentration of LPG1 and LPG2 is about 10 ppmV, and the composition is as follows.
S compounds in LPG cylinders: CH ₃ SH, C ₂ H ₅ SH, (CH ₃ ) ₂ S, C ₃ H ₇ SH, C ₄ H ₉ SH, (CH ₃ ) ₃ CSH, COS (LPG2 only)
Gas was extracted from the upper extraction part of a 50 kg cylinder filled with LPG, and the sulfur concentration in LPG was analyzed with respect to LPG consumption by gas chromatograph (detector FPD) and ultraviolet fluorescence method.

  From the above results, it was found that although the concentration of S was hardly changed from the initial stage to 70% consumption for both LPG 1 and 2, high concentration of S was discharged after 90% consumption. This is because the sulfur content contained in LPG is emitted from the light gas, whereas the sulfur content is heavier than LPG (mainly propane), so it is mainly concentrated in the liquid phase of LPG. This is probably because the high concentration S is discharged as the residual LPG decreases.

Example 2
[Desulfurization method A of LPG1]
In the method for desulfurization of LPG 1 shown in FIG. 1, the room temperature desulfurization agent I was pressure molded to about 2 mm as room temperature desulfurization agents 1A and 1B. Two cold desulfurization agents 1A and 1B were installed in parallel on the assumption that the cylinder 2 was used to the end. With respect to 50 cc of room temperature desulfurization agent I, LPG1 was circulated with a contact time of GHSV1000h- ¹ .
When 90% of cylinder 2 with high concentration of S in LPG is consumed, the liquid level meter in the cylinder detects it. When a constant S concentration is supplied, it is supplied to the room temperature desulfurization agent 1A, and at the point of 90% consumption rate of the cylinder where the S component concentration becomes high, switching from the room temperature desulfurization agent 1A to the room temperature desulfurization agent 1B is performed. At the time of switching, the switching valve 7A is closed and the valve 7B is opened. The room temperature desulfurization agent 1B can completely adsorb and remove S even at a high concentration of S. The room temperature desulfurizing agent 1A used 2% by weight of Ag, and the room temperature desulfurizing agent 1B used 13% by weight of Ag.
According to the test results shown in FIG. 2, the S concentration is 0.1 ppm or less (below the detection limit) in all regions by switching the room temperature desulfurization agent 1A to 1B as the inlet S concentration increases when the cylinder consumption rate is about 90%. ) S could be removed. Moreover, when using the normal temperature desulfurization agents II-VI instead of the normal temperature desulfurization agent I as the said normal temperature desulfurization agent 1, it confirmed that it had sufficient desulfurization capability similarly.

Example 3
[Desulfurization method A of LPG2]
A desulfurization test was performed on LPG 2 contained in COS as shown in FIG. In this desulfurization system, a room temperature desulfurization agent and a heating desulfurization agent are arranged in series.
50 cc (GHSV1000h ⁻¹ ) g of the above room temperature desulfurization agent I is installed as the room temperature desulfurization agent 1 in the downstream of the cylinder 2. Further, 5 g (GHSV10000h ⁻¹ ) of the above heat desulfurization agent I is installed in the downstream as the heat desulfurization agent 9. The heated desulfurizing agent 9 was kept at 200 ° C. by the heater 8. The S analyzer monitored the S concentration of both the downstream of the room temperature desulfurizing agent 1 and the downstream of the heated desulfurizing agent 9. A desulfurization test was carried out in the same manner as in Example 2. FIG. 4 shows the test results.
Even when LPG2 is used, the sulfur component containing COS can be completely removed by the heated desulfurizing agent, and the S component that cannot be completely removed by the room temperature desulfurizing agent in the high concentration S component after 90% of the cylinder is consumed. It became clear that it could be completely removed. In addition, when the heat desulfurizing agents II and III were used as the heat desulfurizing agent 9 instead of the heat desulfurizing agent I, the S compound could be completely removed in the same manner.

Example 4
[LPG1 desulfurization method B]
The desulfurization of LPG 1 not containing COS shown in FIG. 6 was performed.
The room temperature desulfurizing agent I is pressure-molded to about 2 mm as the room temperature desulfurizing agent 1, and LPG cylinders are arranged in parallel. With respect to 50 cc of room temperature desulfurization agent 1, LPG1 was circulated with a contact time of GHSV1000h- ¹ . In addition, this room temperature desulfurization agent I carry | supports Ag loading 2%. The desulfurized LPG was sampled and the outlet S concentration was analyzed over time. In addition, when the cylinder 2A in which the concentration of S in LPG is high is 90% consumed, the liquid level meter in the cylinder detects. At this time, the valve 6A is closed, the valve 6B is opened, and LPG is supplied from the other cylinder 2B.

FIG. 7 shows the S component concentration before and after the desulfurization agent over time.
By carrying out the exact time of the cylinder switching process, a constant concentration (about 7 ppmV) of S is supplied to the room temperature desulfurization agent 1 so that the outlet S concentration is S <0.1 ppm (the analyzer's It was below the detection limit) and showed stable desulfurization performance. In addition, when room-temperature desulfurization agents II to VI are used instead of room-temperature desulfurization agent I as the room-temperature desulfurization agent 1, the desulfurization ability is more than a certain level by performing an appropriate switching process in a cylinder parallel arrangement. It was confirmed. Further, the LPG in which the high concentration S component remains can be reused by filling the LPG without adding the S component (odorant) as it is.
On the other hand, when the cylinder is replaced after the LPG cylinder is almost completely consumed as a comparative example, as shown in FIG. 8, since the high concentration of S-containing LPG is supplied to the room temperature desulfurization material at the end of the cylinder, the S content is reduced. Slip to the wake was observed. In this case, the slip S component is not a preferable method because it poisons the reforming catalyst installed downstream.

  According to the present invention, in a supply method using an LPG cylinder, stable desulfurization in LPG can be performed even when the sulfur concentration changes with time in accordance with the S component concentration consumption, unlike city gas. In addition, an efficient fuel cell operation method using LPG having high convenience can be provided. Furthermore, according to one embodiment of the present invention, efficient desulfurization can be achieved even if a sulfur content such as COS that cannot be removed by a room temperature desulfurization agent is contained in LPG.

It is the figure which showed schematic structure of the system which concerns on embodiment (the 1). In the system of Embodiment (the 1), it is the figure which showed the relationship between a cylinder consumption rate and exit sulfur concentration. It is the figure which showed schematic structure of the system which concerns on embodiment (the 2). In the system of Embodiment (the 2), it is the figure which showed the relationship between a cylinder consumption rate and exit sulfur concentration. It is the figure which showed an example at the time of combining the system which concerns on embodiment (the 2) with the reformer for fuel cells. It is the figure which showed schematic structure of the system which concerns on embodiment (the 3). It is the figure which showed the relationship between each cylinder consumption rate and exit sulfur concentration at the time of performing the switching process in the system of Embodiment (the 3). It is the figure which showed the relationship between the cylinder consumption rate at the time of desulfurizing the gas from a LPG cylinder using a desulfurization agent, and an exit sulfur concentration. It is the figure which showed schematic structure of the system which concerns on embodiment (the 1) and (the 3). It is the figure which showed schematic structure of the system which concerns on embodiment (the 2) and (the 3).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Room temperature desulfurization agent 2 LPG cylinder 3 Liquid level meter 4 Supply line 5 Analyzer 6 On-off valve 7 Switching valve 8 Heater 9 Heating desulfurization agent 10, 11 Valve 12 Line 20 Reformer 21 Burner 22 Reforming catalyst 23 Catalyst

Claims (7)

An LPG desulfurization system in which two or more desulfurization agents are installed in series in a flow path of gas flowing from an LPG cylinder,
A room temperature desulfurization agent is disposed on the upstream side with respect to the gas flow direction, and a heating desulfurization agent is disposed on the downstream side ,
The heating desulfurizing agent is provided in the interior of the reformer for a fuel cell, LPG desulfurization system characterized Rukoto is heated by the thermal energy of the internal reformer.   2. The LPG according to claim 1, wherein the room temperature desulfurization agent is one in which silver, copper, or cobalt is supported as a metal component using beta zeolite, X zeolite, Y zeolite, or MFI zeolite as a carrier. Desulfurization system.   The LPG desulfurization system according to claim 1 or 2, wherein the heat desulfurization agent is a metal of Ni, Cu, Zn, or Fe or an oxide thereof. Two or more LPG cylinders are installed in parallel, and each LPG cylinder is provided with detection means for detecting the remaining amount of gas, and the supply gas leading to the desulfurizing agent is provided between the two or more LPG cylinders. LPG desulfurization system according to any one of claims 1 to 3, characterized in that it comprises switching means for switching. The sulfur compound in the LPG cylinder contains at least one selected from the group consisting of dimethyl sulfide, methyl ethyl sulfide, and tertiary butyl mercaptan, according to any one of claims 1 to 4 . LPG desulfurization system. A method of performing desulfurization by providing at least two or more desulfurization agents in series in a gas flow path flowing from an LPG cylinder,
A first desulfurization step of performing a desulfurization treatment in a range of 0 to 50 ° C. using a normal temperature desulfurization agent on the upstream side with respect to the gas flow direction;
A second desulfurization step in which desulfurization treatment is performed in the range of 70 to 500 ° C. using a heated desulfurization agent on the downstream side of the first desulfurization step;
Only including,
When two or more LPG cylinders are installed in parallel, in addition to the above steps,
A detection step of detecting a remaining gas amount in the at least one LPG cylinder consumed by gas circulation and sending a detection signal when a desired consumption rate is reached;
A cylinder switching step of switching the supply gas to at least one other LPG cylinder in a state where a part of the LPG remains in the LPG cylinder according to the detection signal;
LPG desulfurization method comprising including Mukoto a. Furthermore, after the said cylinder switching process, the process of filling other LPG with the remaining LPG as it is in the said cylinder consumed by gas distribution is included, The LPG of Claim 7 characterized by the above-mentioned. Desulfurization method.

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