JP4159864B2 - Method for producing hydrogen-containing gas - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a hydrogen-containing gas by steam reforming a hydrocarbon such as kerosene.
In the hydrogen-containing gas production method, the use of easy material for storage or transportation, such as kerosene, reduced activity of the reforming catalyst is small can be operated continuously, yet operation started, standing hydrogen gas or an inert gas for stopping It is hoped that this is not necessary.
In particular, there is a strong demand for a device that supplies a hydrogen-containing gas to a small fuel cell power generation system.
The present invention will be readily methanol storage or transportation, in combination with oxygen-containing compounds such as ethanol or dimethyl ether, kerosene can reformer while suppressing deterioration of the catalyst, and a driving method do not have to standing hydrogen gas To provide and meet the above requirements.
[0002]
[Prior art]
In conventional hydrogen-containing gas production, if the raw material is hydrocarbon, steam reforming is required using a Ni-based or Ru-based catalyst with a steam ratio of S / C = 3.0 to 4.0, inlet temperature 350 to 450 ° C, and outlet temperature 750 to 850 ° C. Depending on the process, it is manufactured through processes such as CO conversion, carbon dioxide removal, and methanation methanation.
[0003]
When the raw material is methanol, a Cu-based catalyst is used and steam reforming is performed at a steam ratio S / C = 1.5 to 2.0 and 250 to 350 ° C.
[0004]
To reform hydrocarbons, Ni and Ru with the activity of cleaving CC bonds and CH bonds are necessary, but these active species have both methanation activity and hydrocracking activity. Then, H2, CO, and CO2 generated by the reforming reaction are methanated or the reaction between the raw material hydrocarbon and H2 occurs, generating CH4 and consuming hydrogen, so it does not become a hydrogen-rich gas. Therefore, the high temperature region (750 to 850 ° C.) in which the reforming conversion rate of CH 4 becomes high in equilibrium is set.
[0005]
In order to reform methanol, high activity like Ni is unnecessary, and reforming with a Cu-based catalyst is possible in a low temperature region of about 300 ° C.
Since the Cu-based catalyst has low methanation activity and hydrocracking activity, it can be reformed by suppressing methane formation even at such low temperatures, and it has CO conversion activity, so it is convenient to keep CO low.
[0006]
If the raw material hydrocarbon becomes heavier, carbonaceous material will adhere to the reforming catalyst, causing a decrease in activity, and if it is severe, the catalyst will collapse, or the gas flow will deteriorate and the high-temperature steam reforming reaction tube will be overheated and damaged. May cause trouble. (For example, see Patent Document 1)
The raw materials that can be processed stably with less trouble are natural gas and city gas LPG, and a special catalyst with K2O added is used to reform naphtha.
[0007]
[Patent Literature]
Japanese Patent No. 3202441 [0008]
If the reforming process is divided into a low temperature and a high temperature, the hydrocarbon is changed to CH4, H2, CO, CO2 in the low temperature steam reforming process and then treated in the high temperature steam reforming process. Carbon deposition troubles in the reforming process are significantly reduced.
[0009]
The low-temperature steam reforming process is carried out in an adiabatic reactor, and the reaction pressure 10-20 kg / cm2-G reactor inlet temperature and steam ratio are 350-450 ° C S / C = 1.5-2.0 moles / C- Atom naphtha is used at 450-500 ° C and S / C = 1.7-2.0.
[0010]
Steam is added to the low temperature steam reformed gas, and the total steam ratio is about S / C = 3-4moles / C-atom (steam supplied to the low temperature steam reforming reactor and steam added in the high temperature steam reforming reactor Is adjusted to the carbon ratio of the raw material hydrocarbon) and steam reforming is performed at a high temperature at an inlet temperature of 350 to 450 ° C. and an outlet temperature of 750 to 850 ° C. To produce hydrogen-containing gas.
[0011]
At the start of operation of conventional equipment, hydrogen gas is flowed, the catalyst layer is heated with the heat of the gas, the catalyst is reduced and activated, and then the raw materials are supplied in the order of water vapor and hydrocarbons to produce gas Start driving.
[0012]
When the operation is stopped, the supply of hydrocarbons is stopped, hydrogen or an inert gas is supplied and circulated, the temperature is lowered, and the supply of water vapor is stopped at a temperature equal to or higher than the temperature at which the water vapor condenses.
[Problems to be solved by the invention]
[0013]
Hydrogen energy supply, especially hydrogen-containing gas production equipment for fuel cell power generation systems, is easy to transport or store raw materials, is safe and easy to handle, has a low pressure that does not apply to the high-pressure gas control law, and is hydrogen and inert. It is required to make gas unnecessary. Looking at the prior art from this point of view, there are the following problems.
[0014]
(1) Since the transportation / storage is easy and safe, oxygenates and, although we want to kerosene as a raw material, oxygen-containing compounds, expensive is compared with kerosene. Therefore , although kerosene is desired to be used as a raw material, the carbonaceous matter is deposited on the steam reforming catalyst, causing activity degradation.
(2) A combination of low temperature steam reforming and high temperature steam reforming, and reforming using a conventional catalyst, reforming hydrocarbons at a low pressure in an adiabatic reactor causes the reaction temperature to fall within a preferred temperature range (450 ˜500 ° C.). From the balance of the reforming reaction / methanation reaction rate, the endothermic reaction is excellent at low pressure, and a part where the temperature is lower than the inlet temperature is generated, resulting in a large decrease in activity due to carbonaceous adhesion.
(3) Although carbonaceous adhesion can be prevented by increasing the water vapor ratio, increasing the water vapor ratio increases the endothermic reaction and lowers the reaction temperature. Then, it does not solve the problem.
(4) Since there is a limit to many Ni-based reforming catalysts that have been put to practical use in the past, there is an idea to use a Ru-based catalyst, but it is expensive and only the reforming process can be handled. Even if it becomes easy, another process will become a bottleneck.
(5) Hydrogen and inert gas are required at the start and stop of operation. It takes time to start and stop operation.
[0015]
The present invention provides an apparatus and an operation method for solving the above-described problems when a conventional hydrocarbon reforming technique is applied to small and simple hydrogen-containing gas production for a fuel cell power generation system, for example. To do.
[0016]
[Means for Solving the Problems]
We refer to such liquid hydrocarbon kerosene in the raw material, suppress the decrease in activity due to the carbonaceous deposition, to reduce the operation start and stop times, moreover, is not always ready hydrogen gas or an inert gas, hydrogen The problem was solved by carrying out earnest research on the apparatus and operation method for producing the contained gas and combining the following technologies.
[0017]
When the hydrocarbon activity such as kerosene is steam-reformed, the catalytic activity decreases or collapses due to carbonaceous precipitation or adhesion, and the raw material hydrocarbon is heated from the outside before it is sufficiently reformed, causing thermal decomposition. In some cases, the reaction temperature is low and the reforming reaction does not proceed while adsorbing on the catalyst, causing decomposition and polymerization.
[0018]
By performing the two-stage reforming of the low temperature steam reforming and the high temperature steam, the problems of pyrolysis and carbonaceous precipitation are solved because the raw material hydrocarbon is heated to a high temperature in the high temperature steam reforming section.
[0019]
However, the problem is low temperature steam reforming. It is often said that the reaction rate increases exponentially with increasing temperature, but conversely, the reaction rate decreases exponentially with decreasing temperature.
The low-temperature steam reforming catalyst can be used in a wide temperature range of 350 to 500 ° C. if it is an LPG raw material, but the operating temperature range is narrow to 450 to 500 ° C. if it is a naphtha raw material.
Carrying out the reforming reaction at a low pressure and a high steam ratio is excellent because the endothermic reaction is excellent, and when the low-temperature steam reforming reaction is carried out in an adiabatic reactor as in the prior art, the catalyst layer temperature falls below the inlet temperature as the reaction proceeds. The speed decreases, and the gasification (reformation) of the hydrocarbon adsorbed on the catalyst does not proceed, so that the active point is covered and the activity decreases.
[0020]
【Example】
The present inventors have succeeded in solving the above-mentioned problems in the following three points.
By First, as raw materials as methanol, ethanol or oxygen-containing compounds such as dimethyl ether, it can readily modified at low temperatures, yet in which the raw material to promote heat generation, a combination of the kerosene is reformed / gasification, carbonization It is to suppress temperature drop and carbonaceous precipitation when hydrogen is treated alone at low pressure and high S / C. That is, in steam reforming of oxygen-containing compounds, the equilibrium state tends to be higher at the same pressure and S / C than that of hydrocarbons. The temperature drop can be suppressed.
[0021]
As described above, the oxygen-containing compound was adopted with the aim of easily reforming at low temperatures without carbon deposition and becoming an exothermic reaction. However, the hydrogen gas generated by the reforming was adsorbed on the catalyst. It was confirmed that there was an effect of gasifying hydrogen.
Conceptually, the reaction is as follows.
CHx + (2-x / 2) H2 → CH4
[0022]
Second, using a Cu-based catalyst or a zinc-chromium-based catalyst, the oxygen-containing compound alone is subjected to low-temperature steam reforming or decomposition to produce hydrogen-rich gas, H2 / CO / CO2 gas, and the gas and hydrocarbon And reforming by mixing with steam, the methanation reaction, which is the exothermic reaction shown below, is started in the upstream part of the catalyst, recovering heat at a low temperature level, and further reforming hydrocarbon steam in the low temperature reaction zone. It is possible to suppress the temperature reduction of the carbonaceous catalyst layer with a smaller amount of the oxygenated compound used than when the oxygenated compound is added as it is to the steam reforming of the hydrocarbon.
CO + 3H2 → CH4 + H2O
CO2 + 4H2 → CH4 + 2H2O
[0023]
In this first stage, the amount of heat required for low-temperature steam reforming or decomposition of the oxygen-containing compound alone is required, such as by recovering the high-temperature gas generated from high-temperature steam reforming by heat exchange, and specially burning fuel. It is not something to do.
In the steam reforming of methanol, the gas is changed to the above gas by the following reaction.
CH3OH + H2O → CO2 + 3H2
Further, when decomposing methanol, it is changed to the above gas by the following reaction.
CH3OH → CO + 2H2
[0024]
In addition, the low temperature reforming section is divided into two stages, and in the first stage low temperature reforming section, a part of hydrocarbons, a part of oxygen-containing compounds and a part of water vapor are mixed to reduce the temperature as described above. The reformed gas with a small amount can be partially obtained, and in the second stage low temperature steam reforming section, the remaining hydrocarbon and steam are charged. Here, the effect of reducing gas such as H 2 contained in the reformed gas generated by the reforming in the previous stage and having a small temperature drop has the effect of suppressing carbonaceous deposition of the reforming catalyst. In this case, the amount of use can be greatly reduced as compared with the amount of the oxygen-containing compound in the above case.
[0025]
Third, the oxygen-containing compound can be easily reformed / gasified at a low temperature, and a gas capable of generating a reducing gas from the catalyst at a low temperature is generated. Therefore, it is possible to start the reaction by supplying the oxygen-containing compound from a temperature (200 to 250 ° C) level lower than the temperature (450 to 500 ° C) level where the catalyst layer temperature is not sufficient to reform the hydrocarbon at the start of operation. It is to become. Generally, at the start of operation, in the process of raising the temperature to the steam reforming temperature, it takes a long time to supply only steam, which may oxidize the catalyst. However, in the present invention, since the oxygen-containing compound is supplied at an early point (from a low temperature at which the temperature rise does not reach the hydrocarbon reforming temperature), the time during which the catalyst is oxidized is reduced. In addition, if reducing gas is generated, the downstream catalyst can be reduced.
[0026]
Furthermore, when the operation is stopped, the hydrocarbon supply is stopped, and then the supply of oxygenated compounds is continued to a lower temperature, the hydrocarbons in the system are purged, the steam supply is stopped after the product gas is recycled, and the system is in a reducing gas atmosphere Can be stopped. In general, when the operation is stopped, in order to avoid carbon deposition, the hydrocarbon supply is stopped, and the system is purged with steam to drive off unreacted hydrocarbons. In that case, the inside of the system is only H2O and an atmosphere for oxidizing the catalyst is obtained, so that an inert gas is usually often supplied. However, according to the present invention, when the oxygen-containing compound is supplied to a low temperature at which the oxidation rate of the catalyst is slowed, the inside of the system is made an atmosphere of reducing gas, the oxidation of the reforming catalyst is prevented, and the hydrocarbon is supplied to a low temperature In comparison, it is possible to suppress the accumulation and deterioration of carbon on the catalyst, and the configuration of the entire system can be simplified.
In addition, a reforming gas recycling line equipped with a gas pumping mechanism such as a compressor or a blower is provided from the reforming reactor outlet to the inlet, after the water is simply cooled and condensed and dropped, it is reintroduced into the inlet, By recycling the reformed gas, the above effect is further improved.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
Next, FIG. 1 which shows the example of carrying out high temperature steam reforming after mixing methanol and a hydrocarbon and carrying out low temperature steam reforming is demonstrated as one reference form of this invention.
Reference numeral 1 denotes a first tank that stores an oxygen-containing compound such as methanol, ethanol, or dimethyl ether. Here, methanol is stored and can be supplied constantly.
A second tank 2 for storing hydrocarbon fuel is connected to the first tank 1 and can be mixed and supplied.
[0028]
3 is a steam supply unit for supplying steam to a mixed liquid of methanol and hydrocarbon, and the mixed liquid to which the steam is added is subjected to low temperature reforming in the subsequent low temperature steam reforming reactor 4. Next, the high temperature steam reforming reactor 5 performs high temperature reforming.
[0029]
In the operation of this embodiment, methanol as an oxygen-containing compound is supplied from the first tank 1 by a liquid feed pump (not shown), and hydrocarbon fuel is supplied from the second tank 2 and mixed. Steam is supplied to the mixed solution from the steam supply unit 3 and introduced into the low-temperature steam reforming reactor 4 filled with Ru or a Ni-based catalyst (not shown) in this state. Evaporation may be performed after further mixing the mixed fuel with water. After the low-temperature reforming, it is introduced into a high-temperature steam reforming reactor 5 filled with a Ni-based catalyst, reformed into a CO / H2-rich gas, and sent to a subsequent shift converter (not shown).
[0030]
FIG. 2 is another reference form showing the case where high-temperature steam reforming is performed after cracking methanol and then mixing with hydrocarbons to perform low-temperature steam reforming. The difference from FIG. Other points are the same as those in FIG. 1 in that a methanol decomposition reactor 6 for decomposing methanol before mixing with fuel is provided.
[0031]
In the operation of this reference mode, the methanol supplied from the first tank 1 is supplied to a methanol decomposition reactor 6 filled with a Cu-based catalyst or a zinc-chromium-based catalyst, converted into CO / H 2 gas, (The mixing means may be a static mixer or the like.) Water vapor is supplied from the water vapor supply unit 3 to this mixed solution, and in this state, a Ru or Ni-based catalyst (not shown) 2) is introduced into the low-temperature steam reforming reactor 4. Evaporation may be performed after further mixing the mixed fuel with water. After the low-temperature reforming, it is introduced into a high-temperature steam reforming reactor 5 filled with a Ni-based catalyst, reformed into a CO / H2-rich gas, and sent to a subsequent shift converter (not shown).
[0032]
FIG. 3 is an embodiment of the present invention showing a case in which methanol and hydrocarbon are mixed and subjected to low-temperature steam reforming and then high-temperature steam reforming, and the low-temperature steam reforming process is performed in two stages. 2 is that low-temperature steam reforming is performed in two stages, and a first-stage low-temperature steam reforming reactor 7 and a second-stage low-temperature steam reforming reactor 8 are newly provided.
[0033]
In this embodiment, the methanol supplied from the first tank 1 is supplied to a methanol decomposition reactor 6 filled with a Cu-based catalyst or a zinc chromium-based catalyst, converted into CO / H 2 gas, and then the second A part of the hydrocarbon fuel from the tank 2 is mixed (mixing means may be a static mixer or the like). Steam is supplied from the steam supply unit 3 to this mixed solution, and in this state, a Ru or Ni-based catalyst ( (Not shown) is introduced into the first-stage low-temperature steam reforming reactor 7 which is packed. Evaporation may be performed after further mixing the mixed fuel with water. After the first stage low temperature reforming, it enters into the second stage low temperature steam reforming reactor 8 filled with the same catalyst, and then introduced into the high temperature steam reforming reactor 5 packed with Ni-based catalyst. The gas is reformed into H2 rich gas and sent to a shift converter (not shown) in the subsequent stage.
[0034]
In the first low-temperature steam reforming process, a reformed gas with a small temperature drop can be obtained due to the effect of methanol addition. In the second low-temperature steam reforming process, the reformed gas from the previous stage, particularly the reducing gas of H2, The effect makes it possible to suppress catalyst deterioration.
In this case, the amount of methanol used can be greatly reduced.
[0035]
Figure 4 shows an example of the relationship between the reactor inlet temperature and the inlet temperature when steam reforming is performed in an adiabatic reactor, based on chemical equilibrium theory, using hexane (C6H14) as the hydrocarbon. is there. From FIG. 4, the adiabatic reaction at low pressure and high S / C tends to lower the outlet temperature compared to the inlet temperature, and it is actually quite difficult to keep the entire reaction temperature at 450 to 500 ° C. I understand.
[0036]
FIG. 5 shows, as an example of the effect of the present invention, a case where two kinds of methanol raw materials are treated for steam reforming of hexane (C6H14).
C6H14 = 100kgmoles / Hr
H2O = 1800kgmoles / Hr (equivalent to S / C = 3)
Pressure P = 0.1kg / cm2-G
For steam reforming of
A case where methanol = 100 kgmoles / Hr or 200 kgmoles / Hr is added as it is;
The relationship between the inlet / outlet temperature of the adiabatic reactor is illustrated for the case where it is added after being decomposed as CH3OH → CO + 2H2.
[0037]
【The invention's effect】
As described above, the present invention is to suppress temperature decrease and carbonaceous precipitation when a hydrocarbon is treated alone at low pressure and high S / C. That is, in steam reforming of oxygen-containing compounds, the equilibrium state tends to be higher at the same pressure and S / C than that of hydrocarbons. The temperature drop can be suppressed.
[0038]
As described above, the oxygen-containing compound was adopted with the aim of easily reforming at low temperatures without carbon deposition and becoming an exothermic reaction. However, the hydrogen gas generated by the reforming was adsorbed on the catalyst. It was confirmed that there was an effect of gasifying hydrogen.
[0039]
The methanation reaction, which is an exothermic reaction, starts in the upstream part of the catalyst, recovers heat at a low temperature level, and reduces the hydrocarbon steam reforming catalyst layer temperature in the low temperature reaction region to the steam reforming of the hydrocarbon. It is possible to suppress the oxygen-containing compound with a smaller amount of the oxygen-containing compound used than when the oxygen-containing compound is added as it is.
[0040]
In this first stage, the amount of heat required for low-temperature steam reforming or decomposition of the oxygen-containing compound alone is required, such as by recovering the high-temperature gas generated from high-temperature steam reforming by heat exchange, and specially burning fuel. It is not something to do.
[0041]
A reformed gas with a small temperature drop can be partially obtained. In the second stage low temperature steam reforming section, the remaining hydrocarbon and steam are introduced. Here, the effect of reducing gas such as H 2 contained in the reformed gas generated by the reforming in the previous stage and having a small temperature drop has the effect of suppressing carbonaceous deposition of the reforming catalyst. In this case, the amount of use can be greatly reduced as compared with the amount of the oxygen-containing compound in the above case.
[0042]
Oxygenated compounds can be easily reformed / gasified at a low temperature, and generate a gas capable of producing a reducing gas at a low temperature. Therefore, it is possible to start the reaction by supplying the oxygen-containing compound from a temperature (200 to 250 ° C) level lower than the temperature (450 to 500 ° C) level where the catalyst layer temperature is not sufficient to reform the hydrocarbon at the start of operation. It is to become. Generally, at the start of operation, in the process of raising the temperature to the steam reforming temperature, it takes a long time to supply only steam, which may oxidize the catalyst. However, in the present invention, since the oxygen-containing compound is supplied at an early point (from a low temperature at which the temperature rise does not reach the hydrocarbon reforming temperature), the time during which the catalyst is oxidized is reduced. In addition, if reducing gas is generated, the downstream catalyst can be reduced.
[0043]
Compared with the case where the oxygen-containing compound is supplied to a low temperature at which the oxidation rate of the catalyst is slowed down, the atmosphere in the system is reduced gas, the oxidation of the reforming catalyst is prevented, and further, the hydrocarbon is supplied to the catalyst at a low temperature. Accumulation and deterioration can be suppressed, and the configuration of the entire system can be simplified.
In addition, a reforming gas recycling line equipped with a gas pumping mechanism such as a compressor or a blower is provided from the reforming reactor outlet to the inlet. By recycling the reformed gas, the above effect is further improved.
[Brief description of the drawings]
1 is a schematic configuration diagram of an reference embodiment of the present invention.
FIG. 2 is a schematic configuration diagram of another reference embodiment in which a methanol decomposition reactor is added to FIG.
FIG. 3 is a schematic configuration diagram of an embodiment of the present invention in which the low-temperature steam reforming process is performed in two stages in FIG.
FIG. 4 is a characteristic diagram of reactor inlet and outlet temperatures during hexane steam reforming.
FIG. 5 is a characteristic diagram of inlet and outlet temperatures of a methanol addition reactor during hexane steam reforming.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 1st tank 2 2nd tank 3 Steam supply part 4 Low temperature steam reforming reactor 5 High temperature steam reforming reactor 6 Methanol decomposition reactor 7 First stage low temperature steam reforming reactor 8 Second stage low temperature steam reforming reactor

Claims (2)

A steam reforming process in which liquid hydrocarbons such as kerosene and an oxygen-containing compound of methanol, ethanol, or dimethyl ether are mixed and steam is added to the steam reforming process is a low temperature steam reforming process and a high temperature steam reforming process. The low-temperature steam reforming process is further divided into two stages, the oxygen-containing compound and steam are supplied to the first stage for steam reforming, and the carbonization is performed on the first stage outlet gas. A method for producing a hydrogen-containing gas, characterized in that hydrogen and steam are added and steam reformed in the second stage, and the outlet gas thereof is steam reformed at high temperature. A steam reforming process in which liquid hydrocarbons such as kerosene and an oxygen-containing compound of methanol, ethanol, or dimethyl ether are mixed and steam is added to the steam reforming process is a low temperature steam reforming process and a high temperature steam reforming process. The low-temperature steam reforming process is further divided into two stages, the first stage is supplied with a mixture of the hydrocarbon and the oxygen-containing compound, and steam reforming is performed. A method for producing a hydrogen-containing gas, characterized by adding the hydrocarbon and steam to the second stage to reform in the second stage, and subjecting the outlet gas to high-temperature steam reforming.

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