JPH0647444B2 - Method for producing hydrogen-containing gas - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention mainly relates to hydrocarbons such as natural gas and naphtha,
Or methanol, ethanol, etc. with alcohols,
The present invention also relates to a method for producing a hydrogen-containing gas by reacting a mixed gas containing water vapor in the presence of a catalyst, if necessary.

(Prior Art) As the above-mentioned method, a method using a furnace called a steam reformer shown in FIG. 3 and FIG. 4 has been widely adopted conventionally.

In FIG. 3, a large number of reaction tubes 2 arranged in a row in a furnace 1 are tubes made of a heat-resistant alloy, and the reaction tubes are filled with a catalyst for steam refuming, In addition, the gas containing saturated hydrocarbon and water vapor flows downward from above. A long flame that extends downward from the ceiling of the furnace 1 is formed in the burner 3 provided between the reaction tubes 2 and 2 that are adjacent to each other, and the combustion gas also flows downward.

In the conventional method shown in FIG. 4, a large number of reaction tubes are arranged in one row as in the case shown in FIG. 3, but in this case, the plurality of burners 3 provided on both side walls are radially arranged. The short flame is formed, and the combustion gas flows upward.

In the method using the steam reformer shown in FIGS. 3 and 4, the gas containing saturated hydrocarbons and steam flowing in the reaction tube 2 is heated by the burner 3 from outside the reaction tube 2. However, the reaction in the reaction tube 2 is a very large endothermic reaction, and the reaction rate is remarkably large. The rate of heat supply is the largest factor that governs the reaction rate. From this, increasing the amount of heat transfer per unit area of the reaction tube (hereinafter referred to as heat flux) as much as possible within the heat resistance limit of the reaction tube 2 promotes the reaction, and also improves the capacity of the furnace. The most necessary thing. Therefore, the maximum heat flux of the inlet part where the gas temperature in the pipe is low, which has a margin in the heat resistance limit of the reaction tube, is gradually reduced toward the outlet part, and the average heat flux of the tube is increased. Is desirable. Further, the conventional steam reformer shown in FIGS. 3 and 4 is operated near the heat resistance limit of the reaction tube 2, and has a relatively small capacity burner 3 to prevent overheating or uneven heating.
Although many are provided, their operation and maintenance are considerably complicated.

As described above, the conventional method has the following drawbacks.

(1) In the conventional method, in order to heat the reaction tube with the burner, it is necessary to arrange the reaction tubes at regular intervals, and when processing a large amount of feed gas that makes the furnace large, a reaction that can be arranged in one furnace Since the number of tubes is limited, there are drawbacks such as difficulty in scale-up that requires multiple furnaces.

(2) In the conventional method, since the reaction tube is heated by the burner, no matter how the burner is operated, the heat flux is likely to have a distribution, which is caused by local overheating (heat spot) of the reaction tube. The reaction tube was bent and the phenomenon of blistering due to thermal creep occurred. To prevent such bending and blistering, the pressure of the supply gas is limited, depending on the maximum temperature of the reaction tube.
It was necessary to set it to 0 to 30 kg / cm ² or less.

(3) On the other hand, in consideration of the reframing pressure, in the usual case, the limit of the reaction temperature is about 850 ° C at most,
At this temperature, unreacted hydrocarbons still remain, and the residual amount may be a problem in the downstream synthesis process (ammonia, methanol, gasoline synthesis, etc.). (Considering the synthesis process on the wake side, it is a requirement for the refumae that refining pressure is high, refining temperature is high and unreacted amount is as small as possible. (4) As described above, in the conventional method, a large number of burners having a relatively small capacity are provided in order to prevent overheating or uneven heating due to the burners, but the operation and maintenance of these burners is considerably complicated.

(Problems to be Solved by the Invention) In view of such circumstances, the present invention does not have the drawbacks of the conventional method and has a relatively simple structure, and a large number of reaction tubes can be compactly installed in the furnace, and It is an object of the present invention to provide a hydrogen-containing gas generation reaction method that has a mild combustion condition and is easy to operate and manage, and has a good reaction rate.

(Means for Solving the Problems) In the present invention, the reaction tube is isolated by a material having a good radiation property, and a fluidized bed is used instead of the conventional burner to supply the high temperature gas. The inventors have found that the above can be achieved, and have completed the present invention.

That is, the present invention provides a large number of double-tube type reaction tubes which are filled with a catalyst in an annular space composed of a concentric inner tube and an outer tube and which are vertically arranged in a furnace. -Like material is used to heat the reaction tube by using high temperature gas generated in the combustion zone of a fluidized bed provided at the bottom of the furnace, and hydrocarbons are directed downward from above to the annular space of the reaction tube. Gas containing alcohols, or alcohols and, if necessary, steam, is flowed down, and after the flow direction is reversed at the lower end of the reaction tube, the inner tube is flowed from the lower side to the upper side so that the reaction gas A method for producing a hydrogen-containing gas from a gas containing hydrocarbons or alcohols, which is characterized by performing self-heat exchange.

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. FIG. 1 is a cross-sectional view of the furnace used in the embodiment of the present invention (cross-sectional view taken along the line AA of FIG. 2), and FIG.

In FIG. 1, a large number of double-tube type reaction tubes 4 are arranged in a furnace 5, and they are isolated by a grid 6 made of a material having a good radiation property. As shown in FIG. 2, this furnace 5 has a large number of double-tube type reaction tubes 4 arranged substantially in the center of the furnace 5, a fluidized bed 9 in the lower part of the furnace, and a heat recovery boiler 12 in the upper part of the furnace. It is installed. In FIG. 2, the fuel 14 is supplied to the burner 18 from the bottom of the furnace, while the air or oxygen-containing gas 15 is supplied to the fluidized bed 9 using the heat-resistant solid particles as the heat medium 7 through the dispersion plate 8. Thus, the fuel 14 is burned in the fluidized bed 9 to obtain the high temperature gas 10. The high temperature gas 10 ascends in the furnace 5 to directly heat the outer surface of the reaction tube 4 and, at the same time, once heat the grid 6 made of a material having a good radiation property, and then the grid 6 is heated.
The reaction tube 4 is also heated by radiation from. After the hot gas 10 has heated the reaction tube 4,
After reaching the upper part of the furnace and heating the boiler water 11 to generate high-pressure steam 19 in the heat recovery boiler 12, it is taken out to the outside as furnace outlet combustion gas 13.

The pre-reaction mixed gas 16 containing hydrocarbons or alcohols as a raw material gas and, if necessary, steam is supplied from above to the annular space portion of the double-tube reaction tube 4 filled with the catalyst. It As the mixed gas 16 descends in the reaction tube 4, the reaction proceeds due to contact with the catalyst, external heating, and heating from the inner tube wall. Furthermore, when the reaction temperature and the reaction rate reached the maximum, the reaction tube 4
U-turn at the lower end of the inner tube to perform self-heat exchange with the mixed gas flowing in the annular portion through the inner tube wall while rising in the inner tube, and effectively utilize the sensible heat of the mixed gas after the reaction. The reaction product gas 17 containing hydrogen is taken out from the upper end of the inner tube.

As described above, the method of the present invention is highly evaluated in that the refoma, which conventionally occupies a large volume, is made extremely compact, and its feature is that a double tube is provided in a grid composed of porous ceramics having high radiation properties. This is the point of arranging a mold type reaction tube, filling the annular portion with a catalyst, flowing a source gas, and replenishing the reaction tube necessary for the reforming reaction by external heating and self heat exchange. Since it is compact, if the structure of the furnace wall is lined with heat-resistant bricks, heat-insulating brick layers, and if necessary the outermost wall cooling method, fluidized bed combustion under pressure is also possible, and a gas turbine is used as a heat recovery method. It is also possible to connect them to further improve thermal efficiency.

〔Example〕

(Case where hydrocarbons contain water vapor) Outer tube inner diameter 120.0 mm x tube wall thickness 16 mm, inner tube inner tube diameter 30.0 mm x tube wall thickness 3.0 mm, double tube effective length 10.5
Table 1 shows the composition of the inlet / outlet of the reactor under the following test conditions using 25 mm Cr-20Ni steel.

Reactor inlet gas temperature 600 ° C Reactor outlet gas temperature 820 ° C Reactor outlet high temperature gas temperature 1200 ° C Reactor outlet pressure (reaction gas side) 30 atm In this example, about 4 times the amount of water vapor is added to methane in natural gas to cause the following reaction.

The catalyst used in this example is 5 to an alumina-silica carrier.
The one impregnated with 6% nickel was used. In the examples, sand was used as the heating medium, and silica brick or carborundum was used as the highly radiative material.

Example 2 (Case where water vapor is included in methanol) Outer tube inner diameter 120.0 mm x tube wall thickness 16 mm, inner tube inner tube diameter 30.0 mm x tube wall thickness 3.0 mm, double tube effective length 10. 5
Table 2 shows the reactor inlet / outlet composition under the following test conditions using m-type SUS-304.

Reactor inlet gas temperature 430 ℃ Reactor outlet gas temperature 480 ℃ Reactor outlet high temperature gas temperature 800 ℃ Reactor gas side outlet pressure 5 ata As the catalyst in this case, a Zn-Cr system was used. Further, sand was used as the heat medium, and alumina ceramics was used as the highly radiative material.

Example 3 (case using methanol as a raw material) A SUS having an outer tube inner diameter of 100.0 mm x tube wall thickness 16 mm, an inner tube inner tube diameter of 25.0 mm x tube wall thickness 3 mm, and a double tube effective length of 8.0 m. Table 3 shows the reactor inlet / outlet composition under the following test conditions using -304.

Reactor inlet gas temperature 320 ° C Reactor outlet gas temperature 350 ° C Reactor outlet high temperature gas temperature 800 ° C Reactor gas side outlet pressure 10 atm CH ₃ OH → CO + 2H ₂ As the catalyst in this case, a Ni-Zn-Cu based catalyst is used, and the heat medium and the material having high radiation properties are the same as in Example 2.

The features of the present invention are shown below.

(1) Compared with the conventional method, a large number of double-tube type reaction tubes can be installed in the furnace, enabling a compact reaction design.

(2) Combustion for heating is carried out in a fluidized bed, and the convective heat transfer from the hot gas and the resulting radiation from the highly radiative grid are used to heat the reaction tube to heat the reaction tube. There are almost no heat spots. Normally, it was necessary to suppress the pressure to about ²⁰ to 30 kg / cm ² , but in the present invention, an upper limit of about 30 to 50 kg / cm ² is possible.

(3) With respect to (2) above, since the reaction tube can be uniformly heated, thermal creep of the reaction tube due to the heat spot and bending due to thermal stress are unlikely to occur.

Therefore, the temperature of the high temperature gas can be raised to about 1200 to 1300 ° C., and after heating the reaction tube in the furnace,
It can be used in gas turbines and waste heat boilers.

[Brief description of drawings]

FIGS. 1 and 2 are for explaining an apparatus used in one embodiment of the present invention. FIG. 1 is a cross-sectional plan view of a steam refiner, and FIG. 2 is a vertical front view.
FIG. 3 and FIG. 4 are diagrams for explaining a conventional device used in this type of method.

Claims (1)

[Claims] 1. A large number of double-tube type reaction tubes which are filled with a catalyst in an annular space composed of a concentric inner tube and an outer tube and which are vertically arranged in a furnace have good radiation properties. The reaction tube is isolated by a grid-like material and heated with hot gas generated in the combustion zone of the fluidized bed provided at the bottom of the furnace, and the annular space of the reaction tube is carbonized downward from above. A gas containing hydrogen or alcohols and, if necessary, water vapor is made to flow down, and after the flow direction is reversed at the lower end of the reaction tube, the inside of the inner tube is made to flow upward from below so that the reaction gas The method for producing a hydrogen-containing gas from a gas containing hydrocarbons or alcohols, which is characterized in that the self-heat exchange is performed.