JPH0363424B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in reactors for reacting fluids in the presence of catalysts. More specifically, when a catalytic reaction involving exotherm or endotherm is achieved to a desired reaction rate under a predetermined pressure and temperature, the reaction heat generated is recovered or the necessary reaction heat is supplied. However, the present invention relates to an improvement in the reactor structure that can bring the temperature distribution of the catalyst layer closer to the optimum distribution required for the process.

The structural disadvantages of conventional reactors will be explained below using methanol synthesis from synthesis gas as an example.

Methanol synthesis using synthesis gas whose main components are carbon monoxide and hydrogen uses a copper-based catalyst at a pressure of 50 to 300 kg/cm ² G and a temperature of 200 to 300°C. Generally speaking, if the reaction heat generated at this time is not removed along the reaction process, the temperature of the reaction gas and catalyst layer will rise excessively.
This results in deterioration of the catalyst, increased production of impurities, and a decrease in the concentration of desired products from the standpoint of chemical reaction equilibrium. For this reason, various methods and structures have been devised to remove the reaction heat and prevent the reaction temperature from rising excessively.

In recent years, as a method for processing the reaction heat, there is a method of cooling the reaction gas and catalyst in the catalyst layer by indirectly transferring the reaction heat to a heat medium. In this case, the heat medium has an appropriate boiling point, latent heat of vaporization,
Evaporative water, organic liquid, etc. having specific heat etc. are used, and the reaction heat is recovered in the form of sensible heat or latent heat of vaporization of these liquids. Practically speaking, the most desirable method is to use water as a heat medium, set the boiling temperature to a temperature lower than the reaction temperature, boil the water under the corresponding saturation pressure to obtain high-pressure steam, and convert the heat of reaction into latent heat of vaporization. The disadvantages of three typical conventional reactors used for this purpose are described below.

The first example is proposed in Japanese Patent Publication No. 58-36572, and FIG. 1 shows a horizontal cross section of approximately the center of the reactor. In this method, ring-shaped refrigerant headers are arranged above and below the catalyst layer 19 in the reactor in FIG. By doing so, the tube sheet is eliminated, and spaces 5 and 6 where no catalyst is present are provided at the outer periphery and center of the cylindrical shell 1, and the reaction gas is radially directed from one of the two spaces to the other. By allowing the gas to flow, the cross-sectional area of gas flow is increased and pressure loss is reduced. At this time, the catalyst layer 19 has an inner circumferential side and an outer circumferential side, respectively.
It is housed between partition walls formed by overlapping a porous plate catalyst receiver 3 and a mesh 4. In addition, in order to absorb the difference in thermal expansion between the pressure-resistant outer shell 1 and the tube group consisting of a large number of heat exchange tubes, the pressure-resistant outer shell 1 and the tube group are configured to be mechanically insulated, and are designed to prevent catalyst particles and uneven flow. The particle-filled layer including the inert particles is supported at its lower part by the bottom of the pressure-resistant shell, and the heat exchange tube is embedded in the packed layer.

Next, the second example is proposed in Japanese Patent Application Laid-Open No. 58-112044, and has almost the same configuration as the first example,
A large number of heat exchange tubes vertically penetrate the catalyst layer one by one, and the reaction gas flows in a radial direction perpendicular to the flow of refrigerant in the heat exchange tubes. 1st example and 2nd example
One of the main differences in this example is that the heat exchange tube group, including its header, is fixed to the upper lid part of the cylindrical pressure-resistant outer shell 1, and the packed bed of particles such as catalyst is the same as in the first example. The lower part is supported by the bottom of the pressure shell.

The third example is proposed in Japanese Patent Application Laid-Open No. 58-112046, and FIG. 2 shows a horizontal cross section of the approximately central portion of this reactor. In FIG. 2, the third example is
The fundamental difference from the previous two examples is that the reactant gas is introduced into the reactant gas supply space 5 in the pressure-resistant shell 1, flows chordally through the catalyst layer 19, and then enters the reactant gas gathering space 6 after the reaction. The feature is that the gas is collected and then taken out to the outside, that is, the reactant gas flows in the string direction. In addition, in FIG. 2, 2 is a heat exchange tube, 4 is a net, and 7 is a refrigerant downcomer pipe.

The following two points are common to the three conventional examples described above. That is, each heat exchange tube penetrates the catalyst layer, in other words, the extra tube gap of the heat exchange tube group is filled with catalyst particles, and is supported directly on the bottom of the pressure-resistant shell. The heat exchange tube group is buried in the catalyst particle layer, that is, the lower part of the catalyst particle layer is supported by the outer shell.

In the following, it will be explained that the above two points cause shortcomings of the conventional reactor.

The first drawback is that the tube gaps in the heat exchanger tube bank become too large in order to achieve sufficient heat transfer area to recover the highest possible level of steam from the reactor without thermally degrading the catalyst. Because of the small size, it becomes difficult to fill the gap with the catalyst and discharge the catalyst from the gap. The filling and discharging of the catalyst can be facilitated by increasing the tube arrangement pitch or decreasing the tube diameter to increase the gap, or by decreasing the catalyst particle diameter, but the heat transfer area per unit volume of the catalyst As a result, the reaction temperature becomes high especially near the inlet of the catalyst layer where the reaction rate is high, resulting in problems such as acceleration of catalyst deterioration and increased production of impurities.
To simply lower the reaction temperature, the temperature of a refrigerant such as boiling water may be lowered, but high levels of steam cannot be recovered. Therefore, in order to secure the necessary heat transfer area, we reduced the pipe diameter and arrangement pitch.
If heat transfer fins are installed, it becomes increasingly difficult to charge and discharge the catalyst, so it is necessary to reduce the catalyst particle size. However, taking catalysts for methanol synthesis as an example, the equivalent diameter is usually 5 to 6 mmφ in consideration of catalyst effectiveness coefficient, pressure loss, manufacturability, etc.
Spherical, cylindrical, or cylindrical particles are used, and if the diameter is made smaller than this, the following problems will occur. In other words, in addition to increased manufacturing costs and increased power costs for compressing the circulating gas due to increased pressure loss, the catalyst layer becomes more likely to become clogged, especially in the lower part of the catalyst layer, and as a result, the reaction gas becomes unevenly flowed. is also likely to occur.

Furthermore, using the case of methanol synthesis as an example, it will be explained using FIGS. 3 and 4 that it is difficult to secure the necessary heat transfer area per unit catalyst volume in a conventional reactor.

Figure 3 shows how 100 kg/kg of reactant gas is fed into a conventional reactor.
cm ² , 240℃, and flowing boiling water at 250℃ (40Kg/cm ² steam recovery) into the heat exchange tube to cool the catalyst layer, which mainly consists of H ₂ and CO, CO _2. The relationship between the average reaction gas temperature in the catalyst layer and the methanol concentration distribution in a conventional reactor is shown when methanol synthesis is performed from synthesis gas. UA in the figure is the overall heat transfer coefficient U (Kcal/m ² h・℃),
Heat transfer area A per unit volume of catalyst (m ² /m ³ of
Cata.), and in Figure 3, UA=80000
(Kcal/h・℃・m ³ of Cata.). As can be seen from Figure 3, the maximum temperature of the reactant gas in the catalyst layer (which can be considered almost the temperature of the catalyst) is approximately 280°C, and this value is higher than the heat resistance temperature of normal copper catalysts, which is 260°C.
320℃, average below 280℃. Conversely, in order to keep the maximum temperature of the catalyst layer below 280℃, the UA must be at least 80000 (Kcal/h・℃・m ³
of Cata.) is necessary.

Figure 4 shows that in methanol synthesis, boiling water is passed through a heat exchanger penetrating the catalyst layer of a conventional reactor, and a reaction gas is flowed in a direction perpendicular to the flow direction of the boiling water, so that the reaction gas generated within the catalyst layer is An example of the relationship between the overall heat transfer coefficient and the gas superficial velocity when the heat of reaction is transferred to boiling water is shown. In general, the method of flowing the reactant gas in a radial or chordal direction, as seen in the conventional apparatus described above, has the advantage that the gas passage area is large, resulting in a lower superficial velocity and lower pressure drop. On the other hand, as shown in FIG. 4, there is a disadvantage that the heat transfer coefficient is also small. If the overall heat transfer coefficient is set to be slightly larger at 800 (Kcal/m ² h・℃), the required heat transfer area A≡80000/800=100 (m ² /m ³ of Cata). By the way, the heat exchange tube has an outer diameter of 25.4 mmφ,
If the tube arrangement is 55 mm square pitch, the minimum gap between adjacent tube walls will be 29.6 mm. This gap has a diameter of 6
The minimum distance (several times the particle diameter) that mmφ catalyst particles can be filled without forming a bridge is approximately 30 mm, so even if 6 mmφ catalyst particles can be filled and discharged, the heat transfer area per unit volume of the catalyst is is approximately 30 m ³ , so the heat transfer area of 100 m is essential for recovering 40 Kg/cm ² steam and keeping the catalyst layer temperature below 280°C, which is necessary to prevent catalyst thermal deterioration and impurity increase. ² cannot be secured. Therefore, with conventional equipment, is it possible to recover steam at low pressure?
Should we accept some degree of catalyst deterioration and increase in impurity generation while keeping the catalyst bed temperature elevated, or if these are not acceptable, should we accept some of the aforementioned problems associated with small particle diameter in exchange for securing a heat transfer area? Alternatively, it may be necessary to take measures such as installing a new small pre-reactor filled with a slightly less active catalyst on the upstream side of the reactor to counteract temperature peaks.

The second drawback is that the lower part of the catalyst particle layer is supported at the bottom of the pressure-resistant shell, and the heat exchange tube group is buried inside the particle layer, so that when the tube group thermally expands, the tube group Differences in the mechanical behavior of the particle layer occur, and near the bottom of the outer shell, particles may break due to compression and consolidation, and excessive stress may act on the tube group, causing problems such as buckling. This phenomenon can be solved by using the same material for the pressure-resistant outer shell and the heat exchange tube as the difference in elongation will be reduced, but if a material that is more inert against impurity generation is used for the heat exchange tube. If the material has a different coefficient of thermal expansion from the material of the pressure-resistant outer shell, the above-mentioned problem becomes more obvious.

The present invention was made in order to eliminate the drawbacks of the conventional devices as described above, and its purpose is to eliminate the need to make the catalyst particle diameter smaller than that of ordinary commercially available products, and to It is easy to discharge, and by securing the heat transfer area as desired, it is easy to set the temperature of the catalyst layer in a temperature range where thermal deterioration and impurity generation are not a problem, and the reaction heat can be converted into high-level thermal energy (such as high-pressure steam). ), and furthermore, to provide a catalyst-filled reactor which can reduce various problems caused by mechanical interaction between the tube group and the catalyst particle layer due to thermal expansion of the heat exchange tube group.

The gist of the present invention is as follows: (1) A reaction in which the reaction gas is caused to flow approximately in the radial direction or approximately in the chordal direction of the reactor while cooling or heating the catalyst layer using heat exchange tubes installed approximately vertically. A catalyst-filled reactor characterized in that catalyst layers and layers of heat exchange tube groups are alternately arranged adjacent to each other.

(2) In a reactor in which the reaction gas is caused to flow approximately in the radial direction or approximately in the chordal direction of the reactor while cooling or heating the catalyst layer using heat exchange tubes installed approximately vertically, the catalyst layer and layers of heat exchange tube groups are arranged adjacently and alternately, a structure including the heat exchange tube groups is fixed to the upper part of the outer shell, and the heat exchange tube groups and the catalyst layer are suspended in the upper part of the outer shell. A catalyst-filled reactor characterized in that the catalyst is housed in a catalyst receiving basket which is housed in the outer shell.

It is in a place where we provide.

Hereinafter, the details of the present invention will be specifically explained with reference to the drawings, based on one embodiment of the catalyst-filled reactor according to the present invention, and taking as an example the case where it is applied to methanol synthesis from synthesis gas.

5 and 6 are explanatory diagrams of one embodiment of the catalyst-filled reactor according to the present invention, and FIGS. 7 and 8 are explanatory diagrams of another embodiment of the catalyst-filled reactor according to the present invention. FIG.

The features of the reactor of the present invention can be summarized in the following two points. That is, the first feature is that a plurality of catalyst layers and layers of heat exchange tube groups are alternately arranged next to each other, and the reaction gas is caused to flow in a direction perpendicular to the flow of the refrigerant. For this reason, there is no need to fill the gaps in the heat exchange tube group layer with catalyst, and the catalyst layer can be constructed by easily filling a relatively wide gap with catalyst particles of normal commercial size. The gas that has heated up due to the adiabatic reaction may be guided to the layer of the heat exchange tube group and cooled. At this time, since no catalyst is filled in the tube group layer, the tube arrangement pitch can be kept sufficiently small, so that the gas flow rate can be increased and the heat transfer coefficient can also take a large value.

The second feature of the reactor of the present invention is that the structure of the cooling tube group is fixed to the upper part of the pressure-resistant outer shell and supported in a suspended form, and the catalyst particle layer is placed in a basket supported on the upper part of the pressure-resistant outer shell. Even if the tube group structure and the basket are made of the same material (such as austenitic stainless steel) and the pressure-resistant outer shell is made of a different material (such as low-alloy steel), the tube This is because it is possible to reduce the problem of mechanical interaction between the tube group structure and the catalyst particle layer due to thermal expansion of the group structure.

A first embodiment example will be described based on FIG. 5. In FIG. 5, reference numeral 1 denotes a cylindrical pressure-resistant outer shell that is placed firmly, and inside it is a basket supported at the upper part of the pressure-resistant outer shell (this includes a partition wall 21 and a perforated plate catalyst receiver from above in the figure). 3, a catalyst receiving bottom plate 22 is integrated into the basket, and inside the basket, tube group layers consisting of a large number of heat exchange tubes 2 and catalyst layers 19 are alternately arranged next to each other, and Each layer of the heat exchange tube group is fixed to the upper part of the pressure-resistant shell 1.

In the above configuration, the behavior of the refrigerant will be explained first. In methanol synthesis, boiling water under pressure is most suitable as a refrigerant, and this type of refrigerant is introduced from the refrigerant supply port 12 and sent to the refrigerant distribution header 9 via the refrigerant downcomer pipe 7 and a plurality of refrigerant conduits 8. After the refrigerant reaches the upper refrigerant collecting header 10 while being distributed to each heat exchange pipe 2 and recovered, the refrigerant is further passed through the refrigerant conduit 8 to the refrigerant gas-liquid drum 11, and then the refrigerant is discharged to the discharge port. Take it out from 13.

Next, the catalyst is introduced from the catalyst filling port 16 in the upper part of the pressure-resistant outer shell 1, and is easily filled into the space between the layers of the adjacent heat exchange tube group by supplying the catalyst to the space between the layers of the adjacent heat exchange tube group. be able to. However, catalyst layer 1
The lower and upper portions of the reactor 9 may be filled with inert solid particles in order to prevent uneven flow of the reaction gas.

When removing a deteriorated catalyst from the reactor after long-term use, two catalyst removal ports 1 are provided at the bottom of each of the pressure-resistant shell 1 and the catalyst receiving basket.
7 should be opened sequentially.

Further, the reaction gas is introduced into the reaction gas supply space 5 on the left side in the figure of the pressure-resistant outer shell 1 via the reaction gas supply port 14, and then flows in a horizontal direction, that is, in an approximately chord direction inside the approximately cylindrical outer shell. Meanwhile, the reaction in the catalyst layer and the cooling operation in the heat exchange group layer are repeated alternately to reach the reaction gas collection space 6 on the right side of the figure of the pressure-resistant outer shell 1, and the gas after the reaction is reacted. Take it out from the gas outlet 15. FIG. 6 shows a cross section taken along the line A-A in FIG. 5. As mentioned above, the catalyst layer 19 and the layers of a large number of heat exchange tubes 2 are arranged alternately, and react with the flow direction of the refrigerant in the heat exchange tubes. The configuration is such that it is almost perpendicular to the gas flow direction (arrow in the figure).

FIG. 7 is an explanatory diagram showing another embodiment of the catalyst-filled reactor according to the present invention, and FIG. 8 is a diagram showing a cross section taken along line AA in FIG. 7.

The symbols in the figure have the same meanings as in FIGS. 5 and 6.

In the second example shown in FIGS. 7 and 8, the catalyst layer 19 and the layers of the tube group consisting of a large number of heat exchange tubes 2 are arranged concentrically and alternately, and the pressure-resistant outer shell 1
A reactive gas supply space 5 is provided at the outermost periphery and a reactive gas gathering space 6 is provided at the center.The reactive gas introduced from the reactive gas supply port 14 first fills the aforementioned reactive gas supply space 5, and then forms a catalyst layer and a reactive gas gathering space 6. The reaction gas is collected in the reaction gas collection space 6 while being repeatedly circulated radially through the layers of the heat exchange tube group to undergo reaction and cooling operations, and then taken out from the reaction gas outlet 15. The second example is the first example shown in Figures 5 and 6.
The difference from the above example is that the flow direction of the reaction gas is radial, and therefore the catalyst layer and the layers of the heat exchange tube group are arranged concentrically. Figure 7,
8, the reaction gas is supposed to flow radially from the outside to the inside, but it is also possible to flow from the inside to the outside if desired.

In the above two embodiments as well, in order to prevent catalyst particles from entering the layer of the heat exchange tube group, both sides of the layer of the tube group may be covered with a net or a perforated plate, or the layers of the tube group may be covered with nets or perforated plates. The gap between the pipe and the pipe may be set to a distance (not more than several times the particle diameter, preferably not more than 2 to 3 times) that makes it difficult for the particles to cross-link and pass through.

What can be said from the above-mentioned operation of the reactor of the present invention is that, as mentioned above, the first feature is that the catalyst can be easily filled and discharged, and that the desired heat exchange tube can be formed regardless of the catalyst filling and discharge. The heat transfer area can be secured, and as a result, the reaction heat can be recovered in the form of high-level thermal energy (high-pressure steam, etc.), and the catalyst layer temperature can be controlled by combining the appropriate catalyst layer thickness and the layer thickness of the heat exchange tube group. Since it is possible to maintain the temperature at or below the catalyst allowable temperature, it is possible to prevent catalyst deterioration and increase in impurity production due to temperature rise.

In addition, as mentioned above, the second feature is that the structure of the catalyst receiving basket and the heat exchange tube group are both fixed at the upper part of the outer shell, and by making the materials of both the same, the thermal expansion of the tube group is prevented. This avoids the possibility of breakage of the catalyst particle layer, compaction, tube buckling, etc., which is caused by this, and also enables the use of an inexpensive material different from that of the tube group as the pressure-resistant outer shell material.

As described above, the reactor of the present invention eliminates the drawbacks of conventional devices, and converts the reaction heat into high-quality thermal energy (such as high-pressure steam), especially in methanol synthesis from synthesis gas that generates heat. Since the catalyst layer can be cooled while being recovered, thermal deterioration of the catalyst and increase in impurity production due to overheating can be prevented, and the catalyst can be easily filled in the catalyst-filled reactor.

[Brief explanation of drawings]

FIGS. 1 and 2 are horizontal sectional views of a conventional vertical reactor, each showing the arrangement of heat exchange tubes found in the conventional apparatus. FIG. 3 is an example of the average reaction gas temperature distribution and methanol concentration distribution in the catalyst layer in a conventional reactor when methanol is synthesized from synthesis gas. Figure 4 shows the case in which the reaction heat generated in the catalyst layer of a conventional reactor is transferred to boiling water in the heat exchange tube in methanol synthesis.
An example of an overall heat transfer coefficient value is shown as a function of gas superficial velocity. Figures 5 and 6 are
FIG. 7 is a diagram showing an example of a specific embodiment of the reactor according to the present invention, and FIGS. 7 and 8 are diagrams showing other embodiments of the present invention. In Figures 5 to 8, 1... pressure-resistant outer shell, 2...
Heat exchange tube, 3... Perforated plate catalyst receiver, 4... Net, 5...
...Reaction gas supply space, 6...Reaction gas collection space,
7... Refrigerant descending pipe, 8... Refrigerant conduit, 9... Refrigerant distribution header, 10... Refrigerant collecting header, 11...
Refrigerant gas-liquid drum, 12... Refrigerant supply port, 13...
Refrigerant discharge port, 14... Reaction gas supply port, 15...
Reaction gas discharge port, 16...Catalyst filling port, 17...
Catalyst outlet, 18... Manhole, 19... Catalyst layer, 20... Particle layer, 21... Partition wall, 22... Catalyst receiving bottom plate.

Claims (1)

[Claims] 1. A reactor in which a reaction gas is caused to flow approximately in the radial direction or approximately in the chordal direction of the reactor while cooling or heating the catalyst layer using heat exchange tubes installed approximately vertically. , A catalyst-filled reactor characterized in that catalyst layers and layers of heat exchange tube groups are arranged adjacently and alternately. 2. Heat exchange with the catalyst layer in a reactor in which the reactor gas is caused to flow approximately in the radial direction or approximately in the chord direction of the reactor while cooling or heating the catalyst layer using heat exchange tubes installed approximately vertically. layers of tube banks are arranged adjacently and alternately, a structure including the heat exchange tube group is fixed to the upper part of the outer shell, and the heat exchange tube group and the catalyst layer are suspended from the upper part of the outer shell. A catalyst-filled reactor characterized in that the catalyst is housed in a catalyst receiving basket housed in the outer shell.