JPS62114644A - Exothermic reaction using double tube reactor - Google Patents

Abstract

PURPOSE:To adjust the temp. in the vicinity of the outlet of a catalyst bed to the b.p. of a cooling liquid or less, by properly regulating the temp. of unreacted supply gas at the inlet of an inner tube and supercooling the cooling liquid in a lower part and boiling the same in an upper part. CONSTITUTION:In performing exothermic reaction using a double tube reactor, the temp. of unreacted supply gas at the inlet of an inner tube is properly adjusted and a cooling liquid is supercooled in a lower part and boiled in an upper part to adjust the temp. of a catalyst bed to the b.p. of the cooling liquid or less in the lower part. By this method, because the unreacted supply gas is supplied to the reactor after the temp. thereof is lowered at least by 10 deg.C, even if a saturated liquid is supplied to a shell, a supercooling region is formed in the shell side and the temp. in the vicinity of the outlet of the catalyst bed can be lowered to the b.p. of the cooling liqiud or less.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an exothermic reaction method using a double tube reactor, and in particular, a method suitable for the following methanol synthesis reaction using a catalyst containing #'l as the main component. Concerning an exothermic reaction method.

[Conventional technology]

It is well known that in order to carry out an exothermic reaction, it is preferable to gradually lower the temperature of the system as the reaction progresses. In a fixed bed catalytic reactor, the temperature distribution within the catalyst layer is
Conventionally, methods have been proposed in which the reactor is lowered from the inlet to the outlet, and the heat of reaction is simultaneously recovered. The method proposed in ``A method for improving equilibrium conditions in methanol production and obtaining high-pressure steam, Japanese Patent Application Laid-open No. 57-55420'' uses a tubular reactor to boil and generate steam on the shell side. However, in order to lower the temperature at the exit of the catalyst layer in terms of reaction equilibrium, it is installed at the middle bottom on the shell side and divided into two chambers, and supercooled water is supplied to the lower chamber to cool the catalyst layer. are doing. This method requires an intermediate bottom on the shell side and is structurally complex;
Since the heat transfer area in the supercooled region is fixed, it is extremely difficult to adjust the outlet temperature from an operational control perspective. Also, as a method of
In this method, a catalyst layer and a group of water tubes are arranged, and adiabatic reaction zones and cooling zones exist alternately, and the temperature is distributed in a zigzag manner instead of gradually lowering the temperature. It gives In order to improve these drawbacks of the reactor, a reactor using double tubes was first developed called "Double tube type exothermic reactor, Japanese Patent Application No. 1982-215724".
and "Reactor, Japanese Patent Application No. 59-080053" have been proposed. In these double tube reactors, boiling liquid for cooling flows through the well side, unreacted supply gas flows through the inner tube of the double tube, and the reactor is surrounded by an inner tube and an outer tube. The reaction gas flows countercurrently with the unreacted supply gas through the catalyst layer filled in the space. Therefore, the catalyst layer is cooled not only by the boiling liquid on the outside but also by the unreacted feed gas in the inner tube, and the temperature can be gradually lowered from the inlet to the outlet. Figure 1 shows a simple structure of a double tube reactor. Unreacted feed gas is introduced through the inlet 1, preheated through the inner tube 2, reversed in the upper channel, passed through the catalyst layer in the reaction tube 3, the reaction proceeds, and taken out through the outlet 4. Coolant is introduced from the shell side port 5 and taken out from the outlet 6 together with steam.

In the conventional cooling method using a boiling liquid in an exothermic reaction using a double tube reactor, it is impossible to cool the temperature of the catalyst layer below the boiling point of the boiling liquid as the cooling liquid.

[Problem that the invention seeks to solve]

The present invention solves the drawbacks of the conventional exothermic reaction method using a double tube reactor, and cools the temperature near the outlet of the catalyst bed by appropriately selecting reaction conditions without modifying the structure of the reactor. The objective is to provide an exothermic reaction method that can lower the temperature below the boiling point of a liquid.

[Means for solving problems]

In the present invention, an inner tube is located in the center of one or more reaction tubes, an annular space surrounded by the reaction tubes and the inner tube is used as a particulate-sized catalyst filling part, and a particle-sized catalyst is filled from the bottom of the inner tube to the upper side. In an exothermic reaction method in which unreacted feed gas flows, gas flows from above to below in the annular catalyst layer, and cooling liquid flows from below to above in the outer shell of the reaction tube, the unreacted By suitably adjusting the inlet temperature of the feed gas to the inner pipe, the coolant is subcooled in the lower part and boiled in the upper part, and the temperature of the catalyst bed is lowered by the boiling point of the coolant in the lower part. This is an exothermic reaction method using a double tube reactor.

[Effect]

By lowering the temperature of the unreacted feed gas by at least 10°C and supplying it to the reactor, even if the saturated liquid is supplied to the shell side, a supercooled region is created on the shell side, and the catalyst layer The temperature near the outlet of the cooling liquid can be lowered below the boiling point. Once the supercooled region is created, the heat transfer between the reaction tube and the cooling liquid on the shell side is close to natural convection, and the overall heat transfer coefficient Uout is the overall heat transfer coefficient between the inner tube and the reaction tube. It is much smaller than the thermal coefficient Uin.

Therefore, the reaction heat in the catalyst layer in the reaction tube is not easily transmitted to the shell-side cooling liquid, and is not easily transmitted to the unreacted supply gas in the inner tube. It is closer to the temperature of the feed gas, and as a result the temperature of the catalyst layer can be lowered below the boiling point of the coolant. Further, near the inlet of the catalyst layer, the amount of heat generated per unit amount of catalyst, that is, per unit heat transfer area is also large, and heat transfer between the reaction tube and the cooling liquid is performed by boiling heat transfer. According to the method of the present invention, a supercooled region can be created in the lower part of the shell side simply by changing the temperature of the unreacted feed gas, and the length of the supercooled region can also be changed by simply changing the temperature of the unreacted feed gas. The temperature distribution near the outlet of the catalyst layer can be freely controlled.

〔Example〕

An example in which the exothermic reaction method of the present invention is applied to a methanol synthesis reaction will be described next.

(1) Unreacted supply gas/composition 00:8.65 molti, H2nia 6.76
Morti a02: 5.51 mol%, aH4
:9. o8mo, z%, supply method 95yu/cr! ?・Supply temperature 150℃ (2) Boiler water as cooling liquid, boiling point 220℃ (5)
5pace Voloity 5000 1/h
(4) Overall heat transfer coefficient between inner tube and catalyst layer: 400 kca17m”h°C (5) Overall heat transfer coefficient between reaction tube and cooling liquid Supercooling region: 5
0 kcal/mFhu Boiling range: 900 kcal
/m'hc (6) Catalyst layer outlet temperature: 195°C By the method of the present invention, the temperature of the unreacted feed gas is increased to 150°C.
When supplied at a temperature of 220° C., the catalyst bed outlet temperature can be lowered to 195° C. while operating at a pressure at the boiler water boiling point of 220° C., creating a favorable reaction equilibrium condition. In this example, the boiling point of the coolant is 25°C lower than the boiling point of 220°C, making it possible to lower the temperature of the catalyst layer and increase the methanol production concentration accordingly. This fulfills the essential requirements for an active catalyst.

FIG. 2 shows the temperature distribution in the double reactor, and the solid line is for a conventional exothermic reaction without any supercooling region. In this case, the catalyst layer outlet temperature 8 of the reaction product cannot be lowered below the boiling point of boiler water, which is the coolant.

On the other hand, the broken line indicates that the unreacted supply gas inlet temperature 7 was lowered to create a supercooled region, and the catalyst layer outlet temperature 8 was able to be lowered to below the boiler water boiling point of the coolant.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a double tube reactor. Figure 2 is a graph showing the temperature distribution inside the reactor, where the solid line is the result of the conventional reaction method without a supercooling region, and the broken line is the result of the method of the present invention with a supercooling region. It is something. Sub-Agents 1) Meifuku Agent Ryo Hagiwara − Sub-Agent Atsuo Anzai

Claims (1)

[Claims] An inner tube is located in the center of one or more reaction tubes, and an annular space surrounded by the reaction tube and the inner tube is used as a particulate catalyst filling part, and unreacted supply gas is supplied from below to above the inner tube. In an exothermic reaction method in which gas flows from the top to the bottom in the annular catalyst layer and a cooling liquid flows from the bottom to the top in the outer shell of the reaction tube, the inside of the unreacted supply gas is By suitably adjusting the inlet temperature to the tubes, it is possible to subcool the cooling liquid in the lower part and boil it in the upper part, so that the temperature of the catalyst layer in the lower part is lowered by the boiling point of the cooling liquid. An exothermic reaction method using a characteristic double tube reactor.