JP3410591B2 - Hydrocarbon steam reforming method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steam reforming method for hydrocarbons, and more particularly to a steam reforming method for hydrocarbons having generally improved thermal efficiency.

[0002]

2. Description of the Related Art The steam reforming of hydrocarbons mainly comprises a steam reforming reaction step represented by the following formula, a desulfurization step as a pre-step for removing the sulfur content in the hydrocarbon, and a CO metamorphic step of converting the H ₂ and CO ₂ is reacted with steam, pressure swing adsorption (PSA), membrane hydrogen purification step by separation methods such as, CO ₂ cleaning process for removing CO _2,
A methanation step is added to convert CO and CO ₂ to methane. C _m H _n + oH ₂ O → pCO + qCO ₂ + rH ₂ + sCH ₄ + zC Conventionally, the steam reforming furnace used in the steam reforming reaction step has a reforming tube filled with a catalyst and a combustion burner. It is performed in the radiation section, and the thermal efficiency in the radiation section is as low as 40 to 60%. For this reason, in order to improve the thermal efficiency of the reforming furnace, a preheating pipe for preheating the raw material and a steam generation pipe are provided in the convection section of the reforming furnace. A method of installing an air preheating system such as Jungstrom is adopted.

The steam, which is a part of the raw material, is supplied by utilizing not only the steam obtained by recovering the heat source of the convection section but also the steam obtained by recovering the heat source of the reformed gas (Fig. 3).

However, in the conventional steam reforming method, (1) it is necessary to dispose the steam generating tube in the convection section as described above, which increases the construction cost. (2) In recent years, it has become possible to lower the S / C (steam / hydrocarbon) ratio as the activity of the reforming catalyst improves, and the excess steam generated in the system tends to increase. , The heat recovery efficiency of the whole process is reduced. (3) The thermal efficiency of the radiation part required for reforming is 40 to 50%,
No further improvement or control of thermal efficiency is possible. (4) Since the thermal efficiency of the radiation portion is as low as 40 to 50%, there are various problems such as the fact that offgas alone is not sufficient as the fuel and a large amount of insufficient fuel is separately supplied.

[0005]

Therefore, an object of the present invention is to improve the thermal efficiency of the radiation section of a steam reforming furnace,
Further, the present invention provides a steam reforming method that can be varied according to the purpose and can efficiently cover the required amount of steam as a raw material.

[0006]

Under such circumstances, the inventors of the present invention have conducted earnest research and as a result, in a steam reforming method for hydrocarbons, a rapid switching heat storage combustion burner system was adopted in a steam reforming furnace. If so, it is possible to improve the thermal efficiency of the radiation part necessary for the reforming reaction, and further,
The inventors have found that the efficiency of the entire process is improved if the reformed gas or blow combustion exhaust gas is used and the thermal efficiency is made variable according to the purpose, and the present invention has been completed.

That is, in the steam reforming method for hydrocarbons according to the present invention, the combustion air is supplied to the burner through the heat storage body in the reforming furnace for carrying out the reforming reaction and the combustion gas is discharged from the burner alternately. A heat switching burner system with a high-speed switching to be carried out is provided, and the amount of heat necessary to generate the amount of preheat and steam of the raw material is covered by the heat recovery from the reformed gas or the blow combustion exhaust gas. It is intended to provide a method for steam reforming of hydrocarbons in which the thermal efficiency of the radiation section can be varied depending on the purpose by adjustment.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The method for steam reforming a hydrocarbon of the present invention is not particularly limited and can be carried out by a known method.
Examples of the raw material hydrocarbon include propane, butane, natural gas, naphtha and the like. After heating the mixture of the hydrocarbon and steam to a temperature of 400 to 600 ° C. in a preheater and, if necessary, a desulfurization step, for example, to several to several hundred reforming tubes filled with a nickel-based catalyst. Introduced, about 650
900 ° C, pressure ATM ~ 30 kg / cm ² , S / C 0.7 ~
The steam reforming reaction of hydrocarbon may be performed under the condition of 5.
Taking the case of producing hydrogen as an example, as a post-step of the steam reforming reaction step of hydrocarbon, a conversion step of reacting CO with steam to convert it into H ₂ and CO ₂ , PSA
It is preferable to combine the hydrogen purification step using the method from the viewpoint of improving the hydrogen production efficiency of the entire system.

As the reforming furnace for carrying out the steam reforming reaction used in the method of the present invention, the supply of combustion air to the burner through the reforming tube and the heat storage body and the discharge of combustion gas from the burner are alternately performed. It is necessary to have a fast switching heat storage combustion burner system.

The high speed switching type regenerative combustion burner system used in the present invention may be composed of a pair of burners, a pair of regenerators and a switching device. When a large amount of heat is required, a plurality of sets of combustion systems are used. It is preferably installed in the reforming furnace. The heat storage body is not particularly limited, but a ceramic honeycomb structure can be used, for example. Further, the installation location of the high-speed switching type regenerative combustion burner system in the furnace is not particularly limited, and it may be installed on the same surface of the furnace wall surface or on the opposing furnace wall surfaces (sidewalls), but at different heights. It is preferable that a plurality of sequences are arranged facing each other at a position. Further, it is preferable to install the combustion burner so that the combustion flame is directed to the reforming tube. As a result, the thermal efficiency of the radiation section is significantly improved, and the installation of the steam generation tube or the like in the convection section can be omitted.

In the reforming furnace, it is necessary to install a preheating pipe for the raw material and a blow combustion exhaust gas outlet pipe in the convection section. The raw material to be passed through the preheating pipe may be any of the above-mentioned hydrocarbons, steam or a mixture thereof, but it is particularly preferable to pass a mixture of hydrocarbon and steam.

In the present invention, the amount of heat required to generate the preheat amount of the raw material and the amount of water vapor is covered by the heat recovery of the reformed gas or the blow combustion exhaust gas if necessary by adopting the high speed switching type regenerative combustion burner. The excess steam can be supplied to the CO ₂ removal step. Of these, the amount of heat required to generate the amount of water vapor of the raw material is such that the ratio of the amount of heat recovered from the reformed gas to the amount of heat recovered from the blow combustion exhaust gas is from 10: 0 to 6: 4, preferably from 9: 1. 6: 4,
More preferably, it is efficient to cover in the range of 9: 1 to 7: 3. Further, the amount of preheating of the raw material is not particularly limited, but for example, a raw material of about 200 ° C. is heated to about 40 at the reforming furnace inlet temperature.
The amount of heat required to heat to 0 to 600 ° C. is preferable.

In the present invention, the amount of blow combustion exhaust gas flowing through the blow combustion exhaust gas outlet pipe installed in the convection portion of the reforming furnace is adjusted to make the thermal efficiency of the radiation portion variable according to the purpose. For example, if the opening of the blow combustion exhaust gas is increased by the opening control valve, the fuel consumption increases and the thermal efficiency decreases, but a large amount of water vapor can be generated. / C
The ratio can be increased. Further, the thermal efficiency is improved by reducing the amount of blown combustion exhaust gas flowing out by the opening degree control valve. The above-mentioned blow combustion exhaust gas is preferably released to the atmosphere after heat exchange with the can water of the steam can.

Regarding the fuel supplied to the burner used in the present invention, during steady operation, the off gas generated from the hydrogen purification step downstream of the steam reforming in the fuel is 80 to 80 in terms of calorific value (Kcal / Nm ³ ). 100%, preferably 9
It is preferable to use 0 to 100%, particularly preferably 100%, because it is not necessary to separately supply fuel. The off-gas is, for example, the remaining combustible gas obtained by separating hydrogen in the gas from PSA, and the composition thereof is not particularly limited, but CO, H ₂ , and CO ₂ -containing 1000 to 2000 Kc.
It may be of low calorie such as al / Nm ³ . Further, the reforming furnace preferably has a furnace temperature controller, a furnace temperature detector, a furnace pressure controller, a fan, a stack, and the like.

[0015]

The present invention will be further described below with reference to the examples shown in the drawings, which are merely illustrative and do not limit the present invention.

FIG. 1 shows the reforming furnace of the present invention and the generation of steam.
Indicates the usage route. This reforming furnace 1 has a plurality of reforming tubes 13 filled with catalyst in the reforming furnace, and a preheating tube (not shown in the figure) for the raw material in the convection section, and is used as a hydrocarbon for the raw material (LPG, methane, off gas). The mixture of steam flows in the reforming pipe 13 in a downflow manner. Further, a high speed switching type heat storage combustion burner system 2 including a pair of burners 4, 4 ', a pair of heat storage bodies 3, 3', and a switching device 5 is arranged on the same surface. Here, the structure and combustion method of the fast switching heat storage combustion burner cisnum 2 are not particularly limited, but in the present embodiment, the heat storage body 3,
3'and a burner and a heat storage body which are not burned by alternately burning two sets of 2 units each having integrated burners 4, 4'having a function as a flow path for preheated air and combustion exhaust gas. What is provided so that exhaust gas can be discharged through is used. For example, in FIG. 1, the combustion air passes through the heat storage body 3, is preheated to, for example, 800 ° C. or higher, passes through the burner 4, and burns. Since high-temperature preheated air is used for combustion, combustion can be performed stably even with low-calorie fuel gas, and the excess air ratio can be made smaller than in the conventional method.
The combustion exhaust gas after supplying heat for the reforming reaction is burner 4 '.
The heat is recovered by the heat storage body 3 and discharged. Switching of combustion between the burner 4 and the burner 4'is performed by the switching device 5, and the switching time is short, for example, preferably every 5 to 60 seconds.
Every 0 seconds. The flow of air and flue gas is reversed at each switching. The fuel is supplied by the on-off valves 6 and 7 which operate in synchronization with the switching device 5, and supplies the fuel to the burning burner. The flow rate of fuel is controlled by the control valve 8. The discharge temperature of the combustion exhaust gas can be 200 ° C. or lower if high-calorie fuel is used, and the thermal efficiency of the radiating portion of the reforming furnace in this case is about 90%. Blow combustion exhaust gas line 1
In No. 2, when a low-calorie fuel gas is used, the amount of combustion exhaust gas is large compared to the amount of combustion air, and the heat of combustion exhaust gas cannot be sufficiently recovered. At this time, a part of the high-temperature combustion exhaust gas is extracted in the blow combustion exhaust gas line 12 so that the heat storage body 4,
The amount of flue gas leaving 4'can be reduced and temperatures below 200 ° C are possible. The high temperature combustion exhaust gas from the blow combustion exhaust gas line 12 is used as a high temperature heat source for generating steam, and contributes to the improvement of the thermal efficiency of the entire apparatus, and then joins with the combustion exhaust gas discharged from the heat storage bodies 4 and 4 '. It is discharged outside the system.

On the other hand, steam, which is one of the raw materials, is controlled by the heat of the reforming gas and the opening degree controller 9 without utilizing the heat of the convection section with the adoption of the high-speed switching heat storage combustion system. The heat of the generated blow combustion exhaust gas can be used by the heat exchangers 10 'and 10 to generate steam. For example, CO + H ₂ gas 1000 Nm
^{In a 3} / H oxo gas production plant, a reforming furnace 50
m ³ , 8 reforming tubes, 2 sets of fast switching heat storage combustion system,
Reforming furnace inlet temperature 510 ° C, inlet pressure 21.7 kg / cm ² ,
When the reforming furnace outlet temperature is 843 ° C. and the outlet pressure is 20.4 kg / cm ² , the steam amount of the raw material is 70% due to heat recovery from the reformed gas and 30% due to heat recovery from blow combustion exhaust gas.
(The heat recovery ratio is 7: 3), and it is not necessary to use the heat of the convection section.

Further, in a gas production plant of the same scale as above and under the same conditions, P provided next to the steam reforming step in the burner of the reforming furnace using the high speed switching heat storage combustion system.
When the off gas generated from SA (hydrogen refining process) was used as all the fuel of the steam reforming furnace, the set temperature of the furnace was maintained by stable combustion. Further, Table 1 shows a comparison with the case of a conventional reforming furnace using a normal burner that does not use the high-speed switching combustion system (comparative example).

[0019]

[Table 1]

FIG. 2 compares the temperature inside the conventional reforming furnace using a normal combustion burner with the temperature inside the radiating portion of the reforming furnace using the fast switching heat storage combustion system of the present invention. In the conventional reforming furnace, the temperature distribution in the furnace is uneven as shown by the maximum temperature A near the furnace center from the furnace inlet, and the reforming tube material is determined to have the maximum temperature A as the allowable temperature of the material. . However, according to the present invention, the in-furnace temperature can be made to have a uniform distribution, the in-furnace temperature can be controlled within the allowable temperature range of the reforming tube, and the average in-furnace temperature can be set higher than before. Therefore, the number of reforming tubes can be reduced, and the reforming furnace can be made compact.

[0021]

EFFECTS OF THE INVENTION Since the steam reforming furnace employs the high speed switching type regenerative combustion burner system, it is possible to improve the thermal efficiency only with the radiator. For this reason, it is not necessary to provide a steam generating tube in the convection section of the reforming furnace in order to improve the furnace efficiency as in the conventional case, and the construction cost can be reduced. Further, by adjusting the thermal efficiency of the radiation part, the amount of water vapor of the raw material can be covered by the amount of water vapor by heat recovery from the reformed gas and blow combustion exhaust gas, and it is efficient without generating excess water vapor. Further, during steady operation, the required heat quantity of the reforming furnace can be covered by only the off gas generated from the system by improving the thermal efficiency.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example of a steam reforming furnace used in the method of the present invention and the generation and utilization of steam.

FIG. 2 is a diagram showing a temperature distribution in a reforming furnace.

FIG. 3 is a schematic diagram showing generation and utilization of steam in a conventional steam reforming method.

[Explanation of symbols]

1,101 reforming furnace 2 1 set of high-speed switching type regenerative combustion burner system 3,3 'regenerator 4,4' burner 11,111 steam can 12 blow combustion exhaust gas outlet pipe 13,113 reforming pipe 102 convection section A conventional Maximum temperature B in the reforming furnace of No. 1 in the reforming furnace of the present invention

─────────────────────────────────────────────────── ─── Continued Front Page (72) Takahiro Kobe Kobe 6-6 Kojimachi, Chiyoda-ku, Tokyo Cosmo Engineering Co., Ltd. (72) Masahiko Hirashiro 6-6 Kojimachi, Chiyoda-ku, Tokyo Cosmo Engineering Co., Ltd. ( 72) Inventor Eiichi Aichi 2-2-153, Shirute, Tsurumi-ku, Yokohama-shi, Kanagawa Japan Furnace Industry Co., Ltd. (72) Inventor Kenji Kawate 95, Mukayashiki, Maehara, Inuyama, Aichi Prefecture 264 (56) References JP-A-9-255305 (JP, A) JP-A-9-79568 (JP, A) JP-A 6-211502 (JP, A) JP 59-199502 (JP, A) International publication 94/02784 (WO, A1) Industrial heating 1999, Vol. 36, No. 4, pp. 39-47 Combustion research, 1996, No. 104, pp. 17-18 Energy saving, 1993, Vol. 45, No. 5, pp. 58-62 ( 58) Fields investigated (Int.Cl. ⁷ , DB name) C10L 3/00 Patent file (PATOLIS) JISST file (JOIS)

Claims (3)

(57) [Claims] 1. A method for steam reforming of hydrocarbons, wherein high-speed switching is performed by alternately supplying combustion air to a burner and discharging combustion gas from the burner through a heat storage body in a reforming furnace that performs the reforming reaction. A heat storage burner system is provided, and the amount of heat required to generate the preheat amount and the steam amount of the raw material is covered by heat recovery from the reformed gas or the blow combustion exhaust gas, and the radiation amount is adjusted by adjusting the blow combustion exhaust gas amount. A steam reforming method for hydrocarbons, characterized in that the thermal efficiency of the section is variable according to the purpose. 2. The amount of heat required to generate the amount of preheat of the raw material and the amount of water vapor is set so that the ratio of the amount of heat recovered from the reformed gas to the amount of heat recovered from the blow combustion exhaust gas is in the range of 10: 0 to 6: 4. The method for steam reforming of hydrocarbons according to claim 1, wherein the method is provided. 3. Off gas generated from a hydrogen refining process downstream of the steam reforming process in a fuel is converted into a heat quantity of 80 to 100.
%, And supplies the burner to the burner.