JPH0135690B2 - - Google Patents

Description

[Detailed Description of the Invention] This invention uses a fixed catalyst or adsorbent,
This invention relates to improvements in reaction or adsorption devices that cause gaseous conversion reactions or adsorption.

In this specification, the term ``catalyst or adsorbent'' that comes into contact with the gaseous raw material is simply referred to as ``catalyst'', the resulting ``reaction or adsorption'' is simply referred to as ``reaction'', and ``perforated pipe, perforated plate, or high space'' is used. Hereinafter, the "porous packing" will simply be referred to as the "perforated tube." (Normally, in adsorption, no chemical reaction occurs between the adsorbent and the adsorbed substance.) The reactor type, in which a rigid cylindrical container is filled with a catalyst, can be divided into axial flow and axial flow depending on the direction of gas flow. It is broadly classified into radial flow.

Axial flow is the most commonly used with catalyst packed on shelves, where the gas flows in a central axial direction (often downward). It is shown in Figure 1a.

Radial flow flows radially between inner and outer baskets that are coaxial with the central axis of the container. The top and bottom of the catalyst layer are usually closed off by partition plates - as shown in Figure 1b. Some models omit part of the upper partition plate and allow part of the gas to flow axially. It is shown in Figure 1c.

Axial flow has a simple structure, but as the gas flow rate increases and the amount of catalyst increases, the horizontal cross section must be increased to prevent pressure drop from increasing, and a container with a large diameter is required.

In contrast, with radial flow, the cross-sectional area of the passage can be increased and the length of the passage can be shortened, resulting in a very low pressure drop. This is the most preferred type of device when the gas flow rate is large and the amount of catalyst is large.

However, the structure of the inner and outer baskets, the upper and lower partition plates, etc. is somewhat complicated, and the cost is high. Particularly in cases where the operating temperature is high due to reaction heat, or there is temperature fluctuation, it is necessary to increase the strength of the basket to accommodate the expansion and contraction of the catalyst layer, resulting in a considerable increase in cost.

In the case of Fig. 1c, a part of the upper partition plate is omitted to further increase the flow passage area and to reduce the cost, but the difference from Fig. 1c is not so large.

The present invention provides a radial flow reactor that maintains the most important feature of radial flow, which is a small pressure drop, and that is inexpensive.

The basic idea of the invention is to provide perforated tubes vertically and equidistantly on the inner wall of the container, instead of an outer basket which accounts for a large proportion of the cost.

The upper end of this porous tube opens into the upper space of the catalyst layer, the lower end reaches the lower end of the catalyst layer, and the surrounding area is filled with catalyst. Gas enters through this upper opening and flows out through the pores of the perforated tube into the catalyst layer. By appropriately selecting the dimensions of the porous tube and the diameter and number of holes, it is possible to cause the gas to flow approximately uniformly in the radial direction of the catalyst layer. Further, the number of porous tubes can be designed so that the gas flows evenly, taking into account the total gas amount, the size of the catalyst layer, etc. The flow rate can be adjusted to be uniform by adding some resistance to the hole in the porous pipe and the inlet part of the inner basket. Note that it is desirable to wrap the outside of this porous tube with a wire mesh or the like to prevent the catalyst from clogging the pores.

Also, since the porous tube is deeply buried in the catalyst layer, it is not necessary to fix it in any particular way, but since it may be used during installation, it is better to hold it from the top and bottom from the inner wall. Preferably, the perforated tube is held so that it can extend freely.

A perforated pipe is simply buried and receives almost no load, so it does not require any special specifications or materials; it can be a regular steel pipe with holes drilled in it. Even if a crack or the like were to occur due to hydrogen embrittlement or the like, it would not pose any particular problem.

Although a circular tube is normally used as this perforated tube, other irregularly shaped tubes can also be used. Example 2
As shown in the figure.

A is a normal circular tube, b and c are made from shaped steel, d is a half-split circular tube, and e is a circular tube with a protruding pipe attached to improve gas dispersion.

Moreover, this "porous tube" does not have to be a so-called "tube" whose periphery is closed. That is, it may be a porous plate or a high porosity filler. As shown in FIGS. 2(f) and 2(g), it is sufficient to create a space between the reactor and the wall of the reaction vessel through which the raw material gas flows. As can be seen in the figure, if this perforated plate is closely attached to the wall of the reaction vessel and filled with catalyst, this perforated plate will be pressed against the vessel wall and will become a suitable gas passage. In FIGS. 2b, c, and d, the back cover is not necessarily necessary as long as the catalyst can be prevented from entering the back cover.

Alternatively, a high porosity packing, such as a Luschig ring, may be filled along the vessel wall. Regular filling provides a suitable gas passage.

In this way, this "perforated tube" can be modified in various ways. By using such a simple and inexpensive perforated tube instead of a costly outer basket, a less expensive reactor can be realized without sacrificing any of the advantages of radial flow.

Note that the gas can flow either from the outside to the inside or vice versa. Also in some cases, e.g. in the case of adsorbents,
From outside to inside when adsorbing, from inside to outside when desorbing,
Or, conversely, it can also be used in cases where the direction of gas flow is changed.

Next, it will be explained with reference to the drawings.

FIG. 3 shows an example to which this invention is applied.

In the figure, 1. reaction vessel, 2. upper mirror plate,
3. Lower mirror plate, 4. Porous tube, 5. Inner basket, 6. catalyst, 7. It is an insulating agent.

The raw material gas enters through the inlet 9, most of which enters the perforated tube 4 from above, flows out through the holes in the tube, passes through the catalyst layer, enters the inner basket 5, and exits through the gas outlet 10.

The porous tube is buried from the top to the bottom of the catalyst layer and opens into the space above the catalyst layer. They are placed vertically at equal intervals along the inner wall of the reaction vessel. The amount of gas passing through the catalyst layer must be as uniform and unbiased as possible. For this purpose, it is desirable that the amount of gas flowing out from each porous tube be equal, and even in one porous tube, there should be no bias depending on the location of the tube. The same can be said for the inner basket.

The simplest way to make the flow rate uniform and unbalanced is to make the dimensions of each part the same, and to reduce the passage resistance of the perforated pipe and inner basket.
The resistance should be greater than the passage resistance of the catalyst layer.
In particular, it is important to sufficiently control the distribution of the amount of gas flowing into the inner basket. The greater the ratio between the former and the latter, the better the uniformity. However, if it is made too large, the uniformity will not be as good and the advantage of the radial flow reactor, which is the small pressure drop, will also be lost, so it is important to design it to an appropriate value. .

Another feature of this device in FIG.
There is no partition plate above the catalyst, and the inner basket is buried within the catalyst layer. In the case of such a reaction, the direction in which the gas flows does not particularly matter, as long as it flows as uniformly as possible through the catalyst layer. Therefore, in the case shown in Figure 3, it is meaningless to attach a partition plate to the top.
The gas only needs to pass through the catalyst layer and into the inner basket. If the top of the inner basket is buried in a catalyst layer and all or the sides and the top are gas permeable, the catalyst above the top also acts as a catalyst layer. The amount of gas passing through this area may be determined so that the space velocity of that part is the same as the overall space velocity. Although the actual dimensions are determined based on these conditions, the upper partition plate and the upper part of the inner basket are no longer necessary, and the cost is reduced accordingly.

In such a case, if the upper part of the catalyst layer is filled horizontally, the part of the catalyst outside the upper part will have a greater distance from the top of the inner basket, making it difficult for gas to pass through. In other words, this part becomes a dead space and is almost unrelated to the reaction. It is wasteful to store valuable catalysts in such ineffective areas. In order to eliminate this waste, the upper part may be made spherical so that the distance from the top of the inner basket is approximately equal. By doing so, the flow of gas from the spherical surface, through the catalyst layer, and into the inner basket is substantially uniform, and the catalyst is all effective.

However, it would be inconvenient to leave the top surface spherical like this. This is because there is a high risk of the mountain collapsing during long-term driving. In order to prevent this, the space between the spherical surface and the horizontal plane passing through its top may be filled with a non-catalytic or non-adsorptive packing 8.

For example, alumina balls or porcelain Ratschig rings are suitable. It is desirable to use a filling through which gas can easily pass. Covering the surface of the catalyst layer with such a filler also serves as a suitable particle suppressor, and is particularly effective when gas flows from the bottom to the top.

It is desirable that the upper surface of the inner basket be spherical or semi-circular, as this will ensure uniform gas flow and is advantageous in terms of strength.

Yet another feature of the apparatus shown in FIG. 3 is the absence of a lower catalyst shelf or partition. In axial flow reactors it is common practice to pack the particles onto support shelves. Even in radial flow devices, it is common practice to install a support shelf or partition plate on which the catalyst is packed. See Figures 1b and c.

The catalyst support shelf or partition plate bears not only the load of the catalyst but also the load corresponding to the pressure drop when gas flows downward from the top, so it supports a considerable load, resulting in considerable cost. In the case of a radial flow reactor, such a shelf or plate is not required if the catalyst is packed directly onto the lower end plate. Problems with gas flow can be avoided by carefully designing the shape of the perforated pipe, inner basket, lower end plate, etc. From the point of view of gas flow, a semi-elliptical or dish-shaped lower end plate is more suitable than a hemispherical end plate.

In the case of an exothermic reaction, depending on the temperature, it is desirable to place a heat insulating material on the lower end plate. For example, when the raw material gas flows from the outside to the inside, the closer the end plate is to the center, the higher the temperature of the gas comes into contact with the end plate, which may impair the mechanical strength of the end plate or cause damage to the material.

In such a case, a heat insulating material 7 can be placed on the lower end plate to prevent the temperature of the end plate from rising too much.

As a heat insulating material for this purpose, a plate-shaped inorganic heat insulating material is suitable. All you have to do is spread this on top of the mirror board and then cover it with insulation bricks, etc.

If the temperature rises even higher, full-scale lining will be necessary, but in that case the insulation adheres closely to the steel, so it is usually not possible to inspect the surface of the steel. Since the heat insulation method of this invention simply places a heat insulating material on the mirror plate, if inspection is required, the heat insulating material can be removed and inspected easily.

If the reaction temperature is not very high, this is sufficient for heat insulation to protect the head plate, and the strength of the head plate material can be considered to be the same as that of the body of the container. In this case, in order to keep the temperature of the end plate as low as possible, it is better not to keep it warm on the outer surface of the end plate.

It is important to be careful as the area near the gas outlet will come into contact with the high temperature reaction gas and the temperature may rise locally. Measures such as providing insulation or changing the material may be necessary.

As described above, FIG. 3 includes all the requirements of claims 1 to 4.
In the case of only the first item, the outer basket in FIG. 1b is simply replaced with a perforated tube, and is therefore not shown in the drawing.

It is a common method to cool the catalyst layer using a cooling pipe through which a cooling heat medium flows. Although it is rarely used in adsorption equipment, it is often applied to reaction equipment that generates a large amount of heat of reaction.

The device according to the invention can also be equipped with this cooling pipe. In many cases, the heat medium is water and cooling tubes form a boiler. In order to ensure uniform gas flow and temperature distribution, it is desirable that the cooling pipes be arranged perpendicular to the catalyst layer on one or more concentric circles having the same center as the central axis of the container, each at equal intervals. .

The method for installing this cooling pipe is the same as that for this type of reactor, so a detailed explanation will be omitted, but one that can be generally used is one equipped with a bayonet type boiler.

Next, an example to which this invention is applied will be introduced.

Carbon monoxide high temperature conversion reactor Raw material gas Hydrogen, nitrogen, carbon monoxide, water vapor mixed gas Inlet temperature 370°C Outlet temperature 440°C Pressure 30Kg/cm ² g What is shown in Figure 3 applies directly to this example.

The reaction raises the temperature, which poses problems in terms of the strength of the end plate material and hydrogen embrittlement. Therefore, a heat insulating board is placed on top of the lower mirror plate to insulate it.

Ammonia synthesis equipment This is an intermediate heat exchange cooling type adiabatic reaction equipment with three catalyst layers. The catalyst bed has a radial flow, with gas flowing from the outside to the inside. The present invention is applied to this catalyst layer.

The raw material gas enters from the inlet 9 and is heated on the tube side of the heat exchanger 11, with most of the gas flowing from the outside through the perforated tube 4 and a portion of the gas flowing into the catalyst layer from the top to cause an ammonia synthesis reaction. The gas then flows into the shell side of the heat exchanger, where the cooled gas undergoes further reaction in the next catalyst layer, passes sequentially through the catalyst layer and the shell side of the heat exchanger, and finally It exchanges heat and flows out from the outlet 10.

A perforated tube is used in place of the outer basket of the catalyst layer. Further, there is no partition plate on the upper surface of the catalyst layer, and the catalyst is packed in spherical heaps, and the non-catalytic filler is packed so that the upper surface is flat. The final catalyst layer is packed onto a heat insulating material placed on top of the end plate.

The gas temperature at the inlet of the catalyst layer is about 360-380°C, and the temperature at the outlet of the catalyst layer is about 460-400°C.

By applying the present invention, it is possible to reduce the cost of a multistage radial flow reactor. Combined with the effect of the insulation material at the bottom, it becomes possible to design the container based on its strength at high temperatures, a so-called "hot wall design."

The same design as this ammonia synthesizer can be applied to large, low-pressure methanol synthesizers that are currently mainstream.

As explained in detail above, according to the present invention, by using a very simple perforated tube, a radial flow reactor with a very low pressure drop can be realized at low cost.

The present invention can be widely applied to reaction apparatuses filled with catalysts, but is particularly suitable for medium to large-sized reaction apparatuses and adsorption apparatuses.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a conventional device. a... axial flow reactor, b... radial flow reactor,
Upper and lower partition plate device, c... Radial flow reaction device, upper partition plate omitted. FIG. 2 is a sectional view of various porous tubes that can be used in the present invention. a...Circular tube, b...Angle iron and lid, c...
Channel steel and lid, d...Half-split circular pipe and lid, e
...Circular tube with protrusions, f, g...Porous tube. FIG. 3 is a cross-sectional view of a reactor to which the present invention is applied, and FIG. 4 is a cross-sectional view of an ammonia synthesis apparatus to which the present invention is applied. DESCRIPTION OF SYMBOLS 1... Reaction container, 2... Upper end plate, 3... Lower end plate, 4... Porous tube, 5... Inner basket, 6
. . . Catalyst, 7 .

Claims (1)

[Scope of Claims] 1. A rigid reaction or adsorption device in which a gaseous raw material is brought into contact with a fixed bed solid catalyst or adsorbent to cause reaction or adsorption, wherein all or most of the raw material gas is in contact with a fixed bed solid catalyst or adsorbent. In a reaction or adsorption device, the flow flows from the outer side of the layer in a semi-mechanical direction and flows into an inner basket provided coaxially with the central axis of the reaction or adsorption container, or in the opposite direction. has an upper space above the catalyst or adsorbent layer, contacts the inner wall of the reaction or adsorption vessel, reaches from the upper space of the catalyst or adsorbent layer to the lower end of the catalyst or adsorbent layer, and the upper end is above the catalyst or adsorbent layer. A radial flow reaction or adsorption device, characterized in that a number of perforated tubes or perforated plates or high porosity packings open to space are provided evenly and vertically on the inner wall of the reaction or adsorption vessel. 2. The inner basket has a side surface, or a side surface and a top surface, which are formed to allow gas to pass therethrough;
The claim is that the upper end is buried in the catalyst or adsorbent layer to a depth approximately equal to the distance from the perforated tube or plate or high void ratio packing to the inner basket. Radial flow reaction or adsorption device according to paragraph 1. 3 The upper surface of the catalyst or adsorbent layer is filled in a manner similar to a spherical surface centered at the center of the upper end of the inner basket and whose radius is the depth of the catalyst or adsorbent layer up to that point, and the upper space is filled with catalyst or adsorbent. Claims 1 or 2 are filled with a non-catalyst or non-adsorbent filler having low gas passage resistance between one surface of water passing through the center of the upper end of the agent layer and the upper surface of the catalyst or adsorbent layer. A radial flow reaction or adsorption device as described. 4. The catalyst or adsorbent is placed in the space between the perforated tube or plate or high void ratio packing of the reaction or adsorption vessel, and the inner basket, directly on the lower head plate of the reaction or adsorption vessel, or directly on the lower head plate of the reaction or adsorption vessel. A radial flow reaction or adsorption device according to any one of claims 1 to 3, which is filled on top of a heat insulating material placed thereon. 5 A large number of cooling pipes through which a cooling heat transfer medium flows are arranged vertically over almost the entire length of the catalyst or adsorbent layer, and are arranged at equal intervals on concentric circles whose center is the same as the central axis of the reaction or adsorption vessel. A radial flow reaction or adsorption device according to any one of claims 1 to 4.