JPS6177601A - Steam reforming reactor for hydrocarbon - Google Patents

Abstract

PURPOSE:To obtain a heat exchanger type above-described reactor having high thermal efficiency with a simple structure by constructing many fins at the external periphery of external tubes of the reactor to a specific structure. CONSTITUTION:Feed gas enters a top chamber 6 of a vertical cylindrical reactor separated by a tube plate 4 from an inlet 11, passes through a catalyst layer 5 packed in an annular space between external and internal tubes 21, 22 of each reaction tube 2, where the feed gas is reformed, moves upwards through the tube 22 and exits the reactor from an exit 12. On one hand, hot gas for heating, or fuel and O2-contg. gas enter from the inlet, the latter two are burnt in a combustion chamber 8 to form hot gas, moves upwards between tubes 2 having bottom parts being suspended in a bottom chamber 7, and exits from the exit 14. Thus, the tube 2 is heated by the hot gas, and a large amt. of heat necessary for reforming is supplied from outside. In this constitution, vertical finned tubes provided with many fins or stud-shaped fins 23, arranged to form regular polygon at the external periphery of the finned tube, are provided to the external peripheral tubes 21; the tips of each fin are arranged to nearly contact each other.

Description

DETAILED DESCRIPTION OF THE INVENTION [Objective] The present invention relates to a hydrocarbon steam reforming reactor that is compact, has good thermal efficiency, has a simple structure, and is easy to operate and maintain.

[Prior art] A method of producing hydrogen and carbon monoxide by using natural gas, naphtha, or other hydrocarbons as raw materials and performing a steam reforming reaction in the presence of a catalyst is a method of obtaining raw material gases such as hydrogen, ammonia, methanol, etc. It is widely used, and various devices for this purpose have been announced.

A steam reforming reactor commonly used is a box-shaped furnace with many reaction tubes filled with catalyst! ! ! It is a hanging reactor. The reactor of the present invention is different from that in that a reaction tube filled with a catalyst in a two-tubular annular portion is suspended in a reaction vessel. The raw material gas flows through the reaction tube, and the heating gas flows through the reaction vessel to heat the reaction tube from the outside.

Various patent applications have already been filed for this type of steam reforming reactor, and it is basically known.

Some recent ones include:

Japanese Patent Publication No. 57-1482 = 57-127443 〃 59-78904 〃 59-78905 〃 59-78906 The water repellent reforming reaction is an 8-temperature reaction, and the reactor thereof is naturally exposed to high temperatures. One important thing in such a device is that
The structure should be as simple as possible, and the stress in the high temperature part should be as low as possible.

However, in this sense, conventional steam reforming reactors have not always been satisfactory.

The present invention provides a steam reforming reactor that has a simple structure and high thermal efficiency.

[! ! Main structure] FIG. 1 shows a sectional view of the basic configuration of the present invention.

This reactor consists of a reactor body 1, a reaction tube 2, an upper cover 3, and a tube plate 4. The reaction tubes are outer tube 21 and inner tube 22.
The lower end of the outer tube 21 is closed, and the upper end is temporarily firmly attached to the tube sheet 4 and hangs in the reactor body. The inner tube is inserted from the top to almost the lower end of the outer tube. In the annular part between the outer tube and the inner tube,
A catalyst receiver is provided near its lower end, an inner tube is inserted into its center, and the catalyst is filled in its annulus.

As the catalyst, a general granular catalyst for hydrocarbon steam reforming can be used.

Mounted on the outer periphery of the outer tube are fins parallel to the tube axis, stud-like fins, or fins perpendicular to the tube axis with holes on the fins. These reaction tubes are mounted on the tube sheet so that the tips of the fins are closely spaced with the twin tips of adjacent reaction tubes, as far as possible due to structural or manufacturing considerations.

A tube plate 4 is provided in the middle of the reactor, the space between it and the upper cover 3 is an upper chamber 6, and the space between it and the water body 1 is T.
``This is Room I 7.

A source gas inlet 11 and a reformed gas outlet 12 are provided in the upper cover. Of course, separate inlets and outlets are provided for these two gases so that they do not mix. As a device, it is also possible to reverse the entrance and exit. However, since the raw material waste generally has a lower temperature, it is preferable to have a structure in which the raw material waste partially contacts the cover and the reformed gas does not directly contact the upper cover, as shown in the figure. Also, from the standpoint of heat transfer or reaction, it is preferable to reverse the entrance and exit.

At the lower end of the reactor body there is an inlet 13 for heating high-temperature gas or fuel gas and oxygen-containing gas, and near the upper end of the reactor body there is an outlet 14 for hot gas or combustion gas after heating.
is provided. It is desirable that this exhaust port be provided in two stages opposite to the 1801 position in order to prevent the gas flow from becoming uneven.

The basic configuration is as described above, but to describe its function, as shown in FIG. The reformed gas passes through the catalyst layer, turns around at the lower end, rises in the inner tube, and flows out from the reformed gas outlet 12.

The high-temperature gas for heating or the fuel for heating and the oxygen-containing gas enter from the inlet port 13, and the fuel J'3 and the oxygen-containing gas are combusted in the combustion arm of the top part of the main body to become high-temperature gas, and the gas is turned into high-temperature gas. It flows from bottom to top between the holes and flows out from the outlet 14.

The reaction tube is heated by this high-temperature gas, and the heat of large W required for reforming is co-supplied with f from the outside. Then, the raw material gas rises in temperature, causes a reforming reaction, passes through the catalyst layer, and then exchanges heat with the raw material gas while passing through the inner tube, cools down and flows out.On the other hand, the high temperature gas has a considerably lower temperature. and leak to the outside.

In this way, this reactor has a structural design in which the reaction section that requires the highest temperature is in contact with the hottest gas of the hot gases, and the tube sheet and upper chamber are in contact with the gas at a relatively mild temperature. It has a reasonable structure.

[Detailed structure 1 Next, details will be explained in more detail.

In a typical box-type steam reforming reactor, heat is transferred to the reaction tube mainly by radiation, which achieves a high heat transfer coefficient.

However, in a heat exchanger type reactor such as the reactor of this invention, convection heat transfer is the main method, and a heat transfer coefficient that high cannot be expected. Especially when the heated high-temperature gas is at normal pressure, heat transfer is not good.

, In cases where heat transfer is insufficient, finned tubes are generally used to widen the heat transfer surface.

In the case of this invention, vertical fins, that is, fins parallel to the tube axis, are generally suitable from the viewpoint of high temperature gas flow. However, fins perpendicular to the tube axis can also be used if the fins are provided with many circular, oval or rectangular holes to provide gas passages. Stud-like fins mounted at right angles to the outer wall of the tube can also be used.

In a normal vertical fin tube, fins of the same height are attached radially at equal pitches on the circumference. When reaction tubes with such fins are placed closely together, the second
As shown in the figure, this is the basic configuration of our invention.

However, a triangular dead space is created where the three circles connecting the tips of the fins intersect. In this part, gas only flows idly and does not contribute equally to heat transfer, so it is preferable to eliminate such a part as much as possible.

'For this reason, we have seen designs such as a heat exchanger in which a spacer is inserted into this triangular part, or a structure in which blocks are piled up to surround the tip of the fin of the reaction tube. These are effective, but the structure becomes very complicated, and the entire device is not compact, making it unattractive.

As a result of our study on heat transfer in the fin duplex, we found that by using a fin tube 7 with a regular polygonal fin tip as shown in Figures 3, 4, 5, and 7, I succeeded in achieving the same effect without using suberly or block materials like Ho.

FIG. 3 shows a cross section of a vertical fin tube in which the tips of the fins are square, and FIG. 4 is a regular hexagon.

If this is done, the height of the fin will vary depending on the location of the cross section. That is, the heat transfer length is different. The amount of heat collected by the fins is proportional to the effective heat transfer length, which is the heat transfer length multiplied by the fin efficiency. Naturally, therefore, an imbalance occurs in the heat 1, and a temperature difference occurs above the outer tube of the reaction tube. That is, a heat flow is generated that flows outward ↑τ in the circumferential direction from the longer side of the fin to the shorter side.

Don't make the difference too big this time! Meat from the outer shell for the rice
It is better not to comb 7 too thinly. Although there are various cases, it cannot be generalized, but it has been found that if the wall thickness is set to a certain culm thickness, heat will flow properly and there will be no problem with Fl.

Comparing the cases of a square and a regular hexagon, the regular hexagon has less unbalance in the natural shape. Unless there is a particular reason, it is preferable to use a regular hexagonal fin tube.

When such a fin tube is used, the effective heat transfer length and the amount of high temperature gas passing through a certain portion of the circumference of the tube are not necessarily proportional. However, from the point of view of the gas temperature, it is preferable to make this ratio as proportional as possible to reduce the unevenness of the gas temperature.C, the flow path area can be changed by making the tips of the fins not radial from the center of the tube, but slightly inclined. It is desirable to make the ratio as approximate as possible.

However, it is difficult to completely adjust this, and the temperature of the humid gas flowing through the fins tends to vary depending on the location. Therefore, the fins are not provided seamlessly over the entire length of the reaction tube, but instead are installed without a fin in the middle. It is preferable to divide it into multiple sections by placing short sections. This is because the hot gases flow through them along the fins, and this short section allows the hot gases to mix and average out the temperatures.

The temperature of the high-temperature gas is low in the part from the bottom of the reaction tube, −
There is no need to install a fin because the width from the top of the tube is strong, and there is no need to install a fin because the high temperature gas must flow across the reaction tube toward the outlet in the part directly below the tube sheet. It's better.

In this invention, the reaction tubes are arranged as close together as possible, but if the tips of the fins are in the right shape, the arrangement is square as shown in Figures 3(b) and 3(c). If it is a regular hexagon, it is arranged in an equilateral triangle as shown in FIG. 4(b).

The model is stud-shaped.
A reaction tube can be used. Here, the fins in the shape of a fin are in the shape of a rivet or rivet, and are welded to the pipe wall.The shape formed by the tip of the fin is the aforementioned square or regular hexagon. An example of this type of fin is shown in Fig. 5. By adjusting the pitch of the mounting studs, the temperature unevenness on the surface of the outer tube of the reaction tube can be minimized.

Fins perpendicular to the tube axis can be used when circular, oval, or outwardly flared rectangular holes are drilled above the fins to provide passage for hot gases.

Square or regular hexagonal fin tips can also be used. FIG. 7 shows an example of this fin.

When stud-like fins or fins perpendicular to the tube axis are used, the short sections without fins in the case of vertical fins described above are not necessary, except for the upper and lower portions of the reaction tube without fins.

The gap between reaction tubes is determined by the amount of deformation of the tubes during use, fI of manufacturing, and assembly! It must be minimized by considering factors such as i degree.

The reactor body is lined with insulation material! I have to, but
Its inner surface must be formed so as to minimize the gap between it and the fins in accordance with the arrangement of the reaction tubes.

In this reactor, the length of the reaction tube is 1
Some are longer than 0m. Since such a long tube is suspended, the upper part is fixed to the tube plate, but the problem arises that the lower part tends to run out and the five adjacent fins collide. In order to apply 1 ton of this 1 tail, hold the bottom edge 1
It is desirable to limit horizontal movement by +i.

For this purpose, a drawing was made in which the reaction tube was held at the F part (the two refractories 25 were oriented horizontally, so that) from the L part to the B F + C 'C'/i, L part. This is reflected in Figures 1 and 6.

As will be described later, it is desirable to provide a distributing chamber 26 in the lower part of the lower chamber of the reactor to ensure that the gas is evenly dispersed. A refractory 25 is placed on top of this horizontally in the same manner as the reaction tubes.The refractory 25 is a briquette-like molded product, and is coaxially placed at the bottom of the reaction tube through a hole in the center. The nine-round bar-shaped protrusion 4 that has been removed will fit into the hole.The fit between the hole and the protrusion should be made so that the gap is as small as possible, and the arrangement of the refractories should match the arrangement of the reaction tubes. to securely secure the bottom of the reaction tube and I k
It can be held at W. There is no problem because the reaction tube is free to stretch in the vertical direction, the refractory is securely held in place by a stabilizer, etc., and the horizontal force is extremely small.

The refractory material is made of refractory bricks, ceramics, ivy, etc.

Note that when temporarily attaching this reaction tube and assembling it by inserting the bundle into this refractory, it may be difficult to assemble it without a template. In such a case, the round rod-shaped protrusion 24 at the bottom of the reaction tube should be placed at right angles to the axis.
7, hold it accurately, and assemble by inserting the protrusion into the refractory with the template 1 attached. This template can be used to burn or melt wood, plastics, aluminum, etc. at high temperatures. Can be used for installation.

It is desirable that the hot gas flows from the bottom of the reactor into each reaction tube as evenly as possible. Therefore, it is preferable to provide a high-temperature gas distributor in the lower part of the lower chamber of the reactor. Although it is not necessary when high-temperature gas is directly introduced, a combustion chamber is necessary when heating fuel 8 and solute-containing gas are introduced and combusted.

As shown in FIG. 911, the lower part of the distributor 26 can be suitably used as the combustion chamber 8.

If this is to be used as a combustion chamber, it is preferable to install a suitable burner and let it burn completely before emptying it into the lower chamber.

Introducing the flame into the lower chamber may cause excessive stress in the reaction tube, so it is preferable to avoid it.

As described in detail above, this reactor is compact and has high thermal efficiency, and can be suitably used for the following purposes.

(1) When the pressure of high-temperature gas is high For example, in the case of high-temperature gas flowing out from the secondary reforming reactor in ammonia plan 1~, the normal pressure is about 30 ka/am (
In the future, the temperature will be as high as 6), and the temperature is before 1000℃.
Cunning.

"High-temperature edge of high-temperature gas furnace (HTGR)" - Mugas.

This reactor is optimal because both pressures are high, the heat transfer of the high temperature gas is good, and the pressure difference between the inside of the reaction tube and the heated high temperature gas is small.

It is also suitable to use combustion gas with high pressure, such as combustion gas for gasters and bottles, for example.

N) When the pressure of high-temperature gas is low In the case of high-temperature gas that has been combusted by combustion under normal pressure or a pressure close to it, a relatively medium to small-sized gas, such as hydrogen 1 runt, fuel cell gasification plan 1-, etc. It is suitable as a reforming reactor.

[Brief explanation of drawings]

Fig. 1 Steam reforming reaction of the present invention Fi 17i side view 2nd
Figure 3 (a) Normal circular vertical finch j2-b arrangement diagram
, Top view of a fir fin duplex with a square fin tip (b) Square arrangement of the same tubes (C) Triangular arrangement of the same tubes Figure 4 (a) Vertical finch with a regular hexagonal fin tip (b) Equilateral triangular arrangement of the same tubes as above. Fig. 5 (a) Cross-sectional view of a tube with sfurado-shaped fins in which the tip of the stud is square. (b) A side view of regular hexagonal chi L-711i as above. Holding device diagram Figure 7 (a) Twin tubes with holes perpendicular to the tube axis (square) (b') Finch holes with holes perpendicular to the tube axis (regular hexagon) 1 Reactor body 2 Reaction tube 3 Upper cover 4 Tube sheet 5 Catalyst 6 Upper chamber 7 Lower part〒8 Combustion chamber 1゛1 Raw material gas inlet 12 Reformed gas outlet 13 High temperature gas inlet for heating 14 lI Discharge port 12゛1 Reaction tube outer tube 22 〃 Inner tube 213 Reaction Tube twin or stud Σ・1 Reaction tube round rod-shaped protrusion 25 Large resistant object 261a Hot gas f chair 1-
Libi'-ter 27 Ten Great Applicant Toyo Engineer? Ring Co., Ltd. Figure 13 Figure 5 (b) Figure 7 (α)

Claims (9)

[Claims] (1) A double-tube structure in which an inner reaction tube whose inner diameter is smaller than the inner diameter of the outer tube and whose lower end is open is inserted from above into an outer reaction tube whose upper end is open and whose lower end is closed. A large number of reaction tubes filled with catalyst in the annular space between the inner and outer tubes are inserted into a vertical cylindrical reactor separated into two chambers, upper and lower, with a tube sheet in the middle. The upper part of the reaction tube is directly opened to the upper chamber of the reactor, and the lower part of the reaction tube is suspended in the lower chamber of the reactor. An inlet for raw material gas, an inlet for heating high-temperature gas or fuel and oxygen-containing gas in the lower part of the lower reactor chamber, and an outlet for this high-temperature gas or combustion gas in the upper part of the lower reactor chamber. The upper end of the inner tube is connected directly to a conduit leading outside the reactor without opening into the upper chamber of the reactor, and a large number of fins or stud-like fins are attached to the outer periphery of the outer reaction tube. A hydrocarbon steam reforming reactor having a structure in which the tips of the fins of adjacent reaction tubes are attached almost to each other. (2) According to claim 1, wherein the fins parallel to the tube axis of the reaction tube are attached so as to form a square whose center is the same as the center of the reaction tube. , hydrocarbon steam reforming reactor. (3) Claim 1, wherein the fins parallel to the tube axis of the reaction tube are attached so as to form a regular hexagon whose center is the same as the center of the reaction tube. , hydrocarbon steam reforming reactor. (4) A plurality of compartments in which fins parallel to the tube axis of the reaction tube are separated by short sections on the top of the reaction tube, excluding a portion directly below the tube plate and a portion from the bottom tip, to which no fins are attached. A hydrocarbon steam reforming reactor according to any one of claims 1 to 3, which is installed in a hydrocarbon steam reforming reactor according to any one of claims 1 to 3. (5) A number of stud-like fins are provided on the outer tube of the reaction tube at right angles to the tube wall, in the shape of a square or regular hexagon with a line connecting the ends of the fins aligned with the center of the reaction tube. A hydrocarbon steam reforming reactor according to claim 1. (6) A fin that is perpendicular to the tube axis of the reaction tube and has many holes on it has a line connecting its tips in the shape of a square or regular hexagon centered on the center of the reaction tube. A hydrocarbon steam reforming reactor according to claim 1, which is provided on an outer reaction tube. (7) A round rod-shaped protrusion is attached to the lower end of the reaction tube coaxially with the reaction tube, and a refractory material with a hole with an inner diameter slightly larger than the outer diameter of the protrusion is attached to the lower part of the lower chamber of the reactor. horizontally,
According to any one of claims 1 to 6, the reaction tubes are arranged in the same manner as the reaction tubes, and the reaction tubes are installed so that the protrusion at the tip of each tube fits into the hole. A hydrocarbon steam reforming reactor as described. (8) made of a material that burns or melts at high temperatures, is placed perpendicular to the central axis of the reaction tube, and is assembled using a template that inserts the round rod-shaped protrusions and maintains their spacing accurately; A hydrocarbon steam reforming reactor according to any one of claims 1 to 7. (9) The hydrocarbon steam reforming reactor according to any one of claims 1 to 8, wherein the lower part of the reactor lower chamber serves as a combustion chamber for the fuel and oxygen-containing gas.