JP2010204017A - Method of detecting anomaly in oxidative reaction process - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of detecting anomaly in an oxidative reaction process allowing a leak of process fluid gas into a heat medium to be rapidly detected in a process of heat exchange between a heat medium and an oxidative reaction process fluid. <P>SOLUTION: In a high-temperature oxidative reaction process using a heat medium, CO gas and/or CO<SB>2</SB>gas are detected in a gas phase part of a heat medium flow path by using a CO/CO<SB>2</SB>detector 5, the CO gas and/or CO<SB>2</SB>gas being evolved owing to the contact of HTS that contains sodium nitrite with a process fluid gas that contains metacrolein or acrolein. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for detecting an abnormality in an oxidation reaction process in which a process fluid of an oxidation reaction leaks into a molten salt as a heat medium in a high-temperature oxidation reaction process in which methacrolein or acrolein is oxidized at a high temperature.

In the heat exchange process, a molten salt is used as a heat medium, and the temperature of the process fluid is adjusted to a predetermined temperature by heat exchange between the heat medium and the process fluid. For example, a molten salt that is a mixture of sodium nitrite (NaNO ₂ ), potassium nitrate (KNO ₃ ), etc. is (1) excellent in heat transfer capacity, (2) chemically very stable even at high temperatures, (3) It has properties such as easy temperature control. For this reason, it is used as a high-temperature heat medium for heating or cooling various process fluids.

  During the heat exchange process, the process fluid may leak into the heat medium from the pipe due to corrosion of the pipe or the like, and various methods have been studied for detecting the leakage of the process fluid. For example, in a heat exchange process between a heat medium and a process fluid, in a heat transfer salt (hereinafter referred to as HTS) which is a molten salt containing sodium nitrite and the like, chlorine, hydrochloric acid, hydrogen sulfide and When a process fluid containing a compound such as methyl mercaptan leaks, a method has been proposed in which leakage abnormality is detected by detecting nitrogen oxides or flammable gas generated by contact with the process fluid ( Patent Document 1).

However, when the process fluid gas of oxidation reaction containing methacrolein or acrolein at high temperature leaks into the HTS, the gas generated by the contact between the gas and the high temperature HTS hardly contains nitrogen oxides. Therefore, it is difficult to detect a leakage abnormality by the above method.
Therefore, there is a possibility that the process fluid gas continues to leak over a long period of time in the HTS at a high temperature, and organic components accumulate in the HTS.

JP 2003-83833 A

  An object of the present invention is to provide an abnormality detection method for an oxidation reaction process capable of quickly detecting leakage of a process fluid gas into the heat medium in a heat exchange process between the heat medium and the oxidation reaction process fluid. is there.

As a result of intensive studies to achieve the above-mentioned problems, the present inventor has found that when a process fluid gas containing methacrolein or acrolein and HTS come into contact with each other at a high temperature, CO gas and / or CO ₂ gas (hereinafter, referred to as “gas flow”). CO gas · CO is that ₂ gas) is focused to generate, by the CO gas · CO ₂ gas detected by the gas phase portion of the heat medium channel, quickly detect leakage of process fluid gas The present inventors have found that this can be done and have completed the present invention.

The present invention provides the following abnormality detection method for an oxidation reaction process.
(1) In a high-temperature oxidation reaction process using a heat medium, CO gas / CO ₂ gas generated by contacting HTS containing sodium nitrite and process fluid gas containing methacrolein or acrolein is used as a heat medium flow path. An abnormality detection method for an oxidation reaction process, characterized in that the detection is performed in a gas phase portion.

(2) The method for detecting an abnormality in the oxidation reaction process according to (1) above, wherein the generated CO gas / CO ₂ gas is detected using a CO / CO ₂ detector.

(3) The abnormality detection method for an oxidation reaction process according to (1) or (2) above, wherein the operating temperature range of the heat medium is 250 to 450 ° C.

According to the abnormality detection method for an oxidation reaction process according to the present invention, a CO gas / CO ₂ gas generated when a heat medium that is a molten salt containing sodium nitrite and a process fluid gas containing methacrolein or acrolein are brought into contact with each other. By detecting this, leakage of the process fluid gas in the high temperature oxidation reaction process can be detected quickly and easily.
This also prevents the process fluid gas from leaking into the HTS for a long period of time and prevents organic components from accumulating, thereby improving the safety of the high-temperature oxidation reaction process of methacrolein or acrolein.

It is the schematic which shows one Embodiment of the abnormality detection method of the oxidation reaction process of this invention. It is the schematic which shows the test apparatus used in the Example of this invention.

Abnormality detection method of the oxidation reaction process according to the present invention, in the high temperature oxidation reaction process for oxidizing methacrolein or acrolein at high temperatures, leak CO / CO ₂ into the heat medium in the process fluid gas containing methacrolein or acrolein It is detected using a detector.

  The high-temperature oxidation reaction process in the present invention mainly refers to a process for producing methacrylic acid or acrylic acid by gas phase catalytic oxidation of methacrolein or acrolein. In addition to methacrolein or acrolein gas, the process fluid gas contains oxygen gas, nitrogen gas, and the like. Normally, the process fluid gas contains about 1 to 10% by volume of methacrolein or acrolein.

In the oxidation reaction process, methacrolein or acrolein is usually oxidized at a temperature of about 250 to 450 ° C. Therefore, HTS which is a molten salt containing NaNO ₂ is used as a heat medium.

As the HTS, a composition containing at least 20 to 90% by weight of NaNO ₂ and having a melting point in the range of about 100 to 200 ° C. is preferable. When using HTS as NaNO _2, NaNO ₃ and KNO a _three compositions, NaNO ₂ 20 to 50 wt%, NaNO ₃ and 5 to 15 wt%, containing in the range of KNO ₃ 45 to 65 wt% Those that do are preferred. Also, when using a composition consisting of NaNO ₂ and KNO ₃ as HTS, NaNO ₂ and 20 to 90 wt%, those containing in a range of KNO ₃ 80 to 10 wt% preferred. Specifically, for example, a composition composed of NaNO ₂ (40% by weight), NaNO ₃ (7% by weight), KNO ₃ (53% by weight) (melting point 142 ° C.), NaNO ₂ (34% by weight), NaNO ₃ ( 13% by weight), a composition comprising KNO ₃ (53% by weight) (melting point 152 ° C.), a composition comprising NaNO ₂ (50% by weight), KNO ₃ (50% by weight) (melting point 139 ° C.) and the like. . Further, water may be added and used in order to lower the freezing point of these HTSs and facilitate the temperature operation.

  In the high temperature oxidation reaction process, for example, a heat exchange type reaction apparatus 1 as shown in FIG. 1 is used. Examples of the heat exchange reactor 1 include, but are not limited to, a multi-tubular catalyst-filled reactor and a plate-type catalyst-filled reactor. Pipes 2 and 3 for sending a process fluid are connected to the heat exchange type reaction apparatus 1. A raw material gas containing methacrolein or acrolein is supplied into the reaction apparatus 1 from the pipe 2, and a fluid containing a reaction product is supplied to the pipe 3. It is discharged from the process and sent to the next process. Moreover, it can replace with the heat exchange-type reaction apparatus 1, and is applicable also when performing heat exchange with a process fluid and HTS with a heat exchanger.

  The HTS whose temperature has risen due to heat exchange with the process fluid in the reactor 1 is discharged from the heat exchanger 1 and sent to the heat medium tank 4 through the pipe 10. A predetermined amount of molten salt is stored in the heat medium tank 4 and is composed of a liquid phase part 6 (HTS) and a gas phase part 7. The molten salt in the liquid phase part 6 is sent to the cooler 9 by the pump 8, cooled, and then supplied to the reactor 1 again.

When the process fluid flow path (partition) in the reactor 1 in the heat exchange process is cracked due to stress or corrosion and the process fluid containing methacrolein or acrolein leaks into the HTS flow path, it is contained in the HTS. Since sodium nitrite has a strong oxidizing action, methacrolein or acrolein is oxidatively decomposed to generate CO gas and / or CO ₂ gas (hereinafter referred to as CO gas / CO ₂ gas).

In order to detect this gas component, leakage of the process fluid is quickly detected by the CO / CO ₂ detector 5 provided in the gas phase section 7. By detecting the CO gas / CO ₂ gas in the gas phase portion of the heat medium flow path, it is possible to detect that the process fluid has leaked into the heat medium. Examples of the heat medium flow path include heat exchangers such as heat exchangers, pipes, tanks, pumps, filters, and related devices. In the present invention, the gas phase portion in the heat medium flow path may be any gas phase portion formed in the above-described device, and includes a vent line thereof.

As the CO / CO ₂ detector 5, an infrared absorption CO / CO ₂ gas detector can be used. Specifically, for example, an infrared gas analyzer manufactured by Yokogawa Electric Corporation can be used.

By detecting the presence of the CO gas / CO ₂ gas in the gas phase section 7 with such a CO / CO ₂ detector 5, the leakage of the process fluid is detected at an early stage. The supply of process fluid and molten salt into the exchanger 1 is stopped. Therefore, it is possible to prevent or suppress the process fluid from continuing to leak over a long period of time and accumulating organic components in the HTS.

  Hereinafter, although an Example is given and the abnormality detection method of this invention is demonstrated, this invention is not limited only to the following Examples.

[Example 1]
The gas generated when a molten salt containing NaNO ₂ and a process fluid containing methacrolein gas were mixed was evaluated.

  FIG. 2 shows a schematic diagram of the whole test apparatus used. As shown in FIG. 2, in the thermostatic chamber 21, a glass container 22 for evaluating the mixing risk of molten salt and methacrolein gas, a molten salt 23 placed in the glass container, and methacrolein gas A supply pipe 35 is provided for supplying the introduced gas containing the gas to the molten salt 23 in the container 22. A pipe 24 for collecting exhaust gas is attached to the glass container 22. A part of the exhaust gas is collected by a Tedlar bag 25 (sampling bag made of a polyfucker vinyl film “Tedlar (registered trademark)” manufactured by DuPont) through a pipe 24.

The introduced gas containing the methacrolein gas is generated by bubbling the O ₂ and N ₂ mixed gas supplied from the O ₂ cylinder 26 and the N ₂ cylinder 27 into the glass container 32 containing the methacrolein 33. It is prepared by mixing the gas in the mixing vessel 34. The glass container 32 is immersed in the cooler 31. The gas flow rates of the O ₂ cylinder 26 and the N ₂ cylinder 27 and the O ₂ and N ₂ mixed gas are measured by gas flow meters 28, 29 and 30. In FIG. 2, P represents a pressure gauge, and T represents a temperature sensor.

The test was performed according to the following procedure using the test apparatus as described above.
(A) Molten salt (NaNO ₂ : 50 wt%, KNO ₃ : 50 wt%) was pulverized, and 50 g was charged into a 100 ml glass container 22.
(B) The glass container 22 was placed in the thermostat 21 and heated so as to have an isothermal temperature of 200 ° C, 280 ° C, or 320 ° C.
(C) An introduced gas (gas volume composition: methacrolein) prepared by mixing a gas generated by bubbling O ₂ and N ₂ mixed gas into a glass container 32 containing methacrolein 33 in a mixing container 34. / O ₂ / N ₂ = 5/5/90) was blown from the pipe 35 into the molten salt 23 at a rate of 30 ml / min.
(D) The gas generated before blowing the introduced gas, 10 minutes after blowing, and 7 hours or 8 hours after blowing was collected in a so-called Tedlar bag 25.
(E) Of the collected exhaust gas, NOx gas was measured by a gas detector tube, and other gases were measured by gas chromatography, and the volume composition of the exhaust gas was examined.

The test results are shown in Table 1. In Table 1, “Macr” indicates methacrolein.

The Table 1, that one can of NOX from exhaust gases were detected most, 280 ° C. and 320 ° C. In CO, the CO ₂ is significantly generated, 200 ° C. but CO, CO ₂ is generated it greatly decrease enough O ₂ concentration becomes high, it is apparent that is progressing oxidation. Therefore, since CO gas and CO ₂ gas were remarkably generated, they should be effective detection gases for detecting leakage of process fluid gas into HTS containing NaNO ₂ in the high-temperature oxidation reaction process of methacrolein. I understand.
Moreover, the gas phase part wall surface of the glass container 22 after the test at 280 ° C. and 320 ° C. was dark brown.

[Example 2]
The gas generated when the molten salt containing NaNO ₂ and the process fluid containing acrolein gas were mixed was evaluated.

Using the test apparatus shown in FIG. 2, acrolein gas was used instead of methacrolein gas, and the test was performed according to the following procedure.
(A) Molten salt (NaNO ₂ : 53 wt%, NaNO ₃ : 7 wt%, KNO ₃ : 40 wt%) was pulverized, and 50 g was charged into a 100 ml glass container 22.
(B) The glass container 22 was placed in the thermostat 21 and heated so as to have an isothermal temperature of 290 ° C.
(C) An introduced gas (gas volume composition: acrolein / O) prepared by mixing a gas generated by bubbling O ₂ and N ₂ mixed gas into a glass container 32 containing acrolein 33 in a mixing container 34 ₂ / N ₂ = 12/4/84) was blown from the pipe 35 into the molten salt 23 at a rate of 30 ml / min.
(D) The gas generated after 2 hours of introduction of the introduced gas was collected in a so-called Tedlar bag 25.
(E) The volume composition of the collected exhaust gas was examined by gas chromatography and a gas detector tube in the same manner as in Example 1.

The test results are shown in Table 2. In Table 2, “Acr” indicates acrolein.

According to Table 2, since CO and CO ₂ are remarkably generated at 290 ° C., it is a detection target gas effective for detecting leakage of process fluid gas into HTS containing NaNO ₂ in the high temperature oxidation reaction process of acrolein. I understand that.

1: reaction device, 2: piping, 3: piping, 4: heat medium tank, 5: CO / CO ₂ detector, 6: liquid phase portion, 7: gas phase portion, 8: pump, 9: cooler, 10 : piping 21: thermostat 22: glass containers, 23: molten salt, 24: piping for collecting the outlet gases, 25: Tedlar bag, 26: O ₂ gas cylinder, 27: N ₂ gas cylinder, 28 and 29 , 30: gas flow meter, 31: cooler, 32: glass container, 33: methacrolein, 34: mixing container, 35: piping

Claims (3)

In a high-temperature oxidation reaction process using a heat medium, CO gas and / or CO ₂ gas generated by contacting a heat medium that is a molten salt containing sodium nitrite and a process fluid gas containing methacrolein or acrolein is used. An abnormality detection method for an oxidation reaction process, characterized by detecting in a gas phase portion of a heat medium flow path. The method for detecting abnormality in an oxidation reaction process according to claim 1, wherein the generated CO gas and / or CO ₂ gas is detected using a CO / CO ₂ detector.   The method for detecting an abnormality in an oxidation reaction process according to claim 1 or 2, wherein the operating temperature range of the heat medium is 250 to 450 ° C.

Images