JP2003265948A - Start-up method of reactor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for efficiently starting up a shell-and-tube reactor without exerting a bad influence on the activity of a catalyst, in which a system for circulating a heating medium of a solid state at normal temperature is adopted. <P>SOLUTION: This shell-and-tube reactor has a reaction tube and a fluid introducing port and a fluid discharging port on the outside of the reaction tube for removing the heat generated in the reaction tube. At first the temperature of the reaction tube is raised by introducing a gas of 100-400°C into the outside of the reaction tube. Next, the heated heating medium is circulated through the outside of the reaction tube. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reactor start-up method, and more particularly to an oxidation reactor for producing (meth) acrylic acid and / or (meth) acrolein by catalytic gas phase oxidation reaction. The present invention relates to a reactor startup method that is preferably used.

[0002]

2. Description of the Related Art In a shell-tube type reactor in which a solid heating medium is circulated at room temperature, the heating medium is circulated in the reactor so that the heating medium is maintained at a temperature equal to or higher than a freezing point to improve fluidity. Must be secured.

Japanese Patent Laid-Open No. 2001-310123 discloses
In a multi-tubular reactor having a reaction tube and an inlet and outlet for a fluid outside the reaction tube for removing heat generated in the reaction tube, a gas having a temperature of 100 to 400 ° C. is introduced to the reaction tube side to raise the temperature. There is provided a reactor start-up method characterized in that the heating medium heated and then heated is circulated outside the reaction tube. As the gas introduced into the reaction tube side, a gas (for example, air, etc.) that has no effect even when mixed with the catalyst or raw material gas contained in the reaction tube
Is to be selected.

However, in the above method, a large amount of high-temperature gas is introduced into the reaction tube side, so that the oxidation state of the catalyst changes. Therefore, the activity and selectivity of the catalyst may be affected, resulting in a decrease in yield and a decrease in catalyst life.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object thereof is to activate a catalyst in a shell-tube type reactor in which a solid heating medium is circulated at room temperature. It is to provide a method for efficiently starting a reactor without adversely affecting the temperature.

[0006]

That is, the gist of the present invention is a shell-tube reactor in which a solid heating medium is circulated at room temperature, and a reaction tube and heat generated in the reaction tube are removed. In a shell-tube reactor having an inlet and an outlet for a fluid outside the reaction tube for heating, a gas having a temperature of 100 to 400 ° C. is introduced to the outside of the reaction tube to raise the temperature, and then the above-mentioned heated. A method for starting up a reactor is characterized in that a heat medium is circulated outside the reaction tube.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below with reference to the accompanying drawings. FIG. 1 is a process explanatory view showing an example of a preferred embodiment of a reactor start-up method according to the present invention.

The present invention is a shell-tube type reactor in which a solid heating medium is circulated at room temperature, and a reaction tube and an inlet port for a fluid outside the reaction tube for removing heat generated in the reaction tube. And a outlet for a shell-tube reactor.

First, the shell-tube type reactor used in the present invention will be described. The shell-tube reactor may be any known reactor as long as it has a reaction tube and an inlet and an outlet for a fluid outside the reaction tube for removing heat generated in the reaction tube. Among them, the multitubular reactor is preferable because it has a high reaction efficiency per volume of the reactor. The multitubular reactor that can be used in the present invention generally has the following structure. That is, the tube plates are provided above and below the reactor shell, the tube plates are clamped at both ends to accommodate a plurality of reaction tubes, and the heat generated in the reaction tubes is removed. It has an inlet and an outlet for external fluid. In the present invention, a barrier plate for partitioning the inside of the reactor shell into a plurality of chambers may be further incorporated.

Next, the heat medium used as the fluid outside the reaction tube in the present invention will be described. The freezing point of the heat medium is usually 50 to 250 ° C, preferably 130 to 180 ° C.
A typical example of such a heat medium is a night game. Among the heat media used for controlling the temperature of the chemical reaction, the niter is particularly preferable in that it has excellent thermal stability, and particularly has the best stability in heat exchange at a high temperature of 350 to 550 ° C. The night game is a so-called molten salt, which has various compositions and different freezing points. In the present invention, any composition of niter can be suitably used as long as it has the above-mentioned freezing point. Examples of compounds used in such a night game include sodium nitrate, sodium nitrite and potassium nitrate, which may be used alone or
A mixture of two or more species can be used.

Next, the features of the reactor startup method according to the present invention will be described. In the present invention, in order to set the temperature in the reactor to the freezing point of the heating medium or higher in advance, a gas having a temperature of 100 to 400 ° C. is introduced to the outside of the reaction tube to raise the temperature. That is, in the case of the method described in the above publication,
The gas for heating the reactor is introduced to the side of the reaction tube filled with the catalyst, but in the case of the present invention, it is introduced to the outside of the reaction tube.
This is a feature of the present invention, and the reactor start-up method according to the present invention does not adversely affect the catalyst. Air is preferably used as the temperature raising gas.

Next, the temperature raising method for the process shown in FIG. 1 will be described. In FIG. 1, the code (5
The reactor indicated by 0) has a first chamber and a second chamber, and in the illustrated example,
The process gas is supplied in a downflow and the heat medium is supplied in an upflow. Lines (L1), (L2), (L3), (L
4) constitutes a process line, and lines (L6), (L
7), (L8), (L9), (L10), (L12),
(L13) and (L14) constitute a heat medium line, and lines (L15) and (L16) are discharge lines used when raising the temperature. In the figure, the symbols ○ ● − and ● ○ − represent spectacle blinds (SB), so-called partition plates,
SB is inserted into the pipe to open and close the flow path. The former symbol represents the open state and the latter symbol represents the closed state.

First, the SB (61) is inserted into the line (L3) (that is, the flow path is closed), and is supplied to the reaction tube side (catalyst layer) of the reactor (50) used during normal operation. The line is closed and SB (62) and SB of line (L5)
(63) is removed (that is, the flow path is opened), and the line (L
1) → blower (10) → line (L2) → line (L
5) → line (L6) → heater (21) → line (L
7) and line (L8) → tank (30) → line (L
A line on the shell side of the reactor (50) consisting of 9) is established. At this time, the valve (71) of the line (L5)
Is closed. In addition, SB of line (L15)
(64) and the valve (72) of the line (L16) are opened to release the introduced gas.

Next, the blower (10) is started, and the gas heated to a temperature of 100 to 400 ° C. by the heater (21) is introduced to the outside of the reaction tube of the reactor (50). The temperature of the reactor (50) is raised by this gas. Reactor (50)
The internal temperature is preferably equal to or higher than the freezing point of the heat medium circulated thereafter, and can be appropriately selected depending on the heat medium used. Generally, the shell side of the reactor (50) is 150
The temperature may be raised until it reaches ˜250 ° C. Because, if the temperature on the shell side is within the above range, even if the heat medium is supplied thereafter, the freezing point of the heat medium is 50 to 250 ° C.,
This is because re-solidification of the heat medium does not occur. On this occasion,
The reaction tube side (catalyst side) is preferably kept in an air atmosphere.

Next, the blower (10) is stopped, and SB (62) of line (L5) and SB (6 of line (L15)
3) is closed and the line (L16) valve (72)
Open the pump, start pumps (41) and (42),
In each chamber, a heat medium is introduced into the first chamber (51) and the second chamber (52) of the reactor (50), and the pump (43) attached in each chamber is used to circulate the heat medium. Raise the temperature of.

It is preferable that each of the above operations be performed quickly. It is preferably performed within 1 hour. If the time is too long, the temperature on the shell side will drop due to heat dissipation, so there is a risk that the heat medium will resolidify when it is introduced.

When heat exchange is performed using a solid heating medium at room temperature, the heating medium is stored in the tank (3) after the reactor (50) is used.
In 0), the entire amount is often recovered. In such a case, the heat medium is
It is stored in the tank (30) without remaining in the reactor (50). Therefore, the heat medium in the tank (30) is heated by the heaters (22) and (23) to such an extent that the fluidity can be secured, and then introduced into the reactor (50).

The heat medium is introduced into the reactor (50) through the following two routes. That is, the heat medium is
The heat medium pump (41) of the tank (30) supplies the first chamber (51) through the lines (L13), (L14), (L6) and (L7), and the tank (3).
It is supplied to the second chamber (52) through the lines (L12) and (L10) by the heat medium pump (42) of (0).

Next, the heat medium introduced into the reactor (50) is circulated in each chamber by an attached pump (43). This is because it may not be possible to raise the temperature in the reactor (50) to the target temperature simply by introducing and circulating the heating medium that is initially heated. for that reason,
The heat medium is circulated, heated by the heater (21), and then introduced again into the reactor (50). For example, chamber 1 (5
1) and the line (L8), the heat medium is led out, and the pump (41) passes through the heater (21) to the line (L).
It is introduced into the reactor (50) via 7).

When the temperature of the reactor (50) can be secured by circulating the heat medium as described above, the raw material gas is supplied to the reaction tube side (catalyst side) to produce the desired product. You can start.

The reactor start-up method according to the present invention is particularly preferable as a start-up method for a reactor used for producing acrylic acid, methacrylic acid, acrolein or methacrolein. The reason is as follows. That is, acrylic acid or the like is a compound that is produced and used in a large amount, and the reactor also increases in size accordingly. Therefore, it is particularly difficult to raise the temperature of the reactor. According to the invention, it is particularly suitable for increasing the temperature during start-up of the reactor when using large reactors.

Acrylic acid is produced by supplying propylene, propane, acrolein or the like as a raw material gas to a known reactor filled with an oxidation catalyst and carrying out a catalytic gas phase oxidation reaction. Generally, a catalytic gas phase oxidation reaction is carried out by allowing a predetermined amount of a molecular oxygen-containing gas and an inert gas to coexist in a source gas. For example, when propylene is used as the source gas, acrolein is produced, and then acrylic acid is obtained by further subjecting this to catalytic vapor phase oxidation.

Known oxidation catalysts can be used as the first-stage and second-stage catalysts in the above-mentioned two-stage catalytic gas-phase oxidation reaction. The shape of the catalyst is also not particularly limited, and may be a ball field, a columnar shape, a cylindrical shape, or the like. In addition, the catalyst may be diluted with a solid inert material before filling. As the solid inert material, α-alumina,
Examples include alundum, mullite, carborundum, stainless steel, copper, aluminum and ceramics.

[0024]

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded.

Example 1 Using the process shown in FIG. 1, a niter having a composition of 40% by weight of sodium nitrite, 7% by weight of sodium nitrate and 53% by weight of potassium nitrate was used as a heat medium and was introduced to the outside of the reaction tube. A multi-tube reactor was started up using air as a working gas. The night gamer was stored in the tank before start-up and did not remain in the reactor. The multi-tube reactor used had an inner diameter of 4500 m.
m reaction tube 130 with a length of 4000 mm
This is a structure in which 00 pieces are supported by the upper tube sheet and the lower tube sheet.
Further, a blocking plate for partitioning the inside of the reactor into two chambers is provided at a position of 300 mm below.

First, each S of lines (L3) and (L5)
Switch between B (61) and (62), blower (10)
From the blower (10) to the heater (21). Then turn on the blower (10) and turn the air to 6
Supply to the heater (21) at a ratio of t / hr and 250 ° C
Preheat to line (L7) and / or line (L8)
From the tank via the tank (30) and the line (L9) to the oxidation reactor (50).

When the temperature of the reactor (50) reached 230 ° C., the blower (10) was stopped and the above SBs were switched. The heaters (22) and (2
The heating medium heated to a temperature of 200 ° C in 3) is pumped (4
It was supplied from the tank (30) in 1) and (42). First
A heating medium is supplied to the chamber (51) from a pump (41) via lines (L13), (L14), (L6), and (L7), and a pump (41) is supplied to the second chamber (52). From 42), the heat medium was supplied via lines (L12) and (L10).

Then, after the heat medium is introduced into the reactor (50), the pump (43) is started to activate the first chamber (5).
The heat medium in 1) was circulated. The temperature of the first chamber (51) is regulated by using the heating medium from the reactor (50) in a line (L).
8), (L13), (L14), and (L6), the heater (21) was supplied to the heater (21), and the reactor (50) was circulated through the line (L7). The temperature of the second chamber (52) was adjusted by the heater (23) attached to the tank (30).

The heat medium temperature of the first chamber (51) is 330.
Since the temperature of the heating medium in the second chamber (52) reached 230 ° C. and reached the predetermined reaction temperature, the operation of the heater (21) was stopped and the startup was completed. It took 40 hours to start up.

Example 2 A shell-tube type reactor having the following structure was used. That is, a double-tube structure made of stainless steel, an inner tube having an inner diameter of 24 mm and a length of 3.5 m, and a Mo (12) Bi (5) Ni (3) catalyst serving as a catalyst in the inner tube. Co (2) Fe
(0.4) Na (0.2) B (0.4) K (0.1) Si (24) O (x) catalyst filled (oxygen composition x is a value determined by the oxidation state of each metal), inner tube A space between the outer tubes is filled with a niter as a heat medium so that a uniform temperature can be maintained by stirring.

Instrumentation air was supplied to the reaction tube at a rate of 1 NL / hr, the shell side temperature was kept at 250 ° C. and maintained for 40 hours, then a 330 ° C. night unit was circulated to contain 9% by volume of propylene as a raw material. The raw material gas was supplied. The propylene conversion rate was 97%, and the total yield of acrolein and acrylic acid was 92%.

Comparative Example 1 The reaction was carried out under the same conditions as in Example 2 except that nitrogen heated to 250 ° C. was fed to the inner tube (catalyst layer) at a rate of 20 L / hr for 40 hours. It was in this case,
The temperature of the niter had to be raised to 340 ° C. in order to achieve a propylene conversion of 97%.

Comparative Example 2 The reaction was carried out under the same conditions as in Example 2 except that the air heated to 250 ° C. was supplied to the inner tube (catalyst layer) at a rate of 20 NL / hr for 40 hours. It was in this case,
The activity of the catalyst changed, a runaway reaction occurred, and the reaction had to be stopped.

[0034]

According to the present invention described above, in a shell-tube type reactor in which a solid heating medium is circulated at room temperature, the reactor can be efficiently used without adversely affecting the activity of the catalyst. A way to get you started,
The industrial value of the present invention is remarkable.

[Brief description of drawings]

FIG. 1 is a process explanatory view showing an example of a preferred embodiment of a reactor start-up method according to the present invention.

[Explanation of Codes] 10: Blowers 21, 22, 23: Heater 30: Tanks 41, 42, 43: Pump 50: Reactor 51: First Chamber 52: Second Chamber L1, L2, L3, L4: Process Line L6 , L7, L8, L9, L10, L12, L13, L
14: Heat medium lines L15, L16: Release lines used when raising the temperature

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C07C 51/21 C07C 51/21 57/05 57/05 (72) Inventor Yasuyuki Ogawa Toho, Yokkaichi City, Mie Prefecture Town No. 1 Mitsubishi Chemical Co., Ltd. In-company (72) Inventor Yoshiro Suzuki No. 1 Toho-cho, Yokkaichi-shi, Mie F-Term (Reference) 4M075 AA03 AA51 AA63 BA01 BA06 BD12 CA02 DA02 DA18 EA06 4H006 AA02 AC46 BD80 BD84 BS10

Claims (3)

[Claims] 1. A shell-tube reactor in which a solid heating medium is circulated at room temperature, the reaction tube and an inlet and a conduit for a fluid outside the reaction tube for removing heat generated in the reaction tube. In a shell-tube reactor having an outlet, a gas having a temperature of 100 to 400 ° C. is introduced to the outside of the reaction tube to raise the temperature, and then the heated heating medium is circulated to the outside of the reaction tube. How to start up the reactor. 2. A heating medium which is solid at room temperature has a freezing point of 50 to 25.
The method according to claim 1, wherein the heating medium is 0 ° C. 3. The method according to claim 1, wherein the shell-tube reactor is a multitubular reactor.