JP2003083833A - Abnormality detection method of heat exchanging process - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an abnormality detection method of a heat exchanging process capable of detecting a leak of process fluid quickly and easily, in the heat exchanging process between a heat medium and the process fluid. SOLUTION: In this heat exchanging process for exchanging heat between the heat medium and the process fluid, a gas component generated by contact between the heat medium and the leaked process fluid is detected by a gas detector 5 in a gas phase part 7 in a heat medium tank 4. For example, the heat medium is a fused salt including sodium nitrite, and the process fluid includes one or more kinds of compounds selected from a group comprising chlorine, hydrochloric acid, hydrogen sulfide and methyl mercaptan, and the generated gas component is a nitrogen oxide or a combustible gas.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an abnormality detecting method in a heat exchange process between a heat medium and a process fluid.

[Prior art]

In the heat exchange process, molten salt, water or the like 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 which is a mixture of sodium nitrite, potassium nitrate, etc. (1) has excellent heat transfer ability,
(2) It is chemically stable even at high temperatures, and (3) it is easy to control the temperature. For this reason,
It is used as a high temperature heating medium for heating or cooling various process fluids.

However, during the heat exchange process, the process fluid may leak from the pipe due to corrosion of the pipe or the like. Therefore, various methods have been studied to detect the leakage of the process fluid. For example, a method has been proposed in which the reaction heat generated when a leaked process fluid reacts with a heat medium is detected by temperature measurement. However, with this method, it takes a considerable amount of time for the temperature to rise to the level at which an abnormality can be detected after the process fluid has leaked, so when the abnormality is detected, the heat medium, process fluid, etc. have already leaked to the outside. There was a risk of a secondary disaster such as an explosion or explosion.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for detecting abnormality in a heat exchange process, which can quickly detect leakage of the process fluid in the heat exchange process between the heat medium and the process fluid. Is.

[0005]

A method for detecting abnormality in a heat exchange process according to the present invention is generated by contact between a heat medium and a leaked process fluid in a heat exchange process for exchanging heat between a heat medium and a process fluid. The gas component to be detected is detected at the gas phase portion in the heat medium flow path. Thereby, the leakage of the process fluid can be detected quickly.

In the method of the present invention, the heat medium is a molten salt containing sodium nitrite (NaNO ₂ ), and the process fluid is at least one compound selected from the group consisting of chlorine, hydrochloric acid, hydrogen sulfide and methyl mercaptan. Is particularly effective when the gas component generated is nitrogen oxide or a flammable gas. That is, the heat medium is Na
In the case of a molten salt containing NO ₂ , nitrogen oxide gas and flammable gas are generated by the reaction between this heat medium and the process fluid. By detecting these gases, it is possible to quickly detect the leakage of the process fluid. Examples of the nitrogen oxide gas include NO gas, NO ₂ gas, N ₂ O gas and the like. Examples of the flammable gas include dimethyl sulfide, carbon disulfide, methane, hydrogen sulfide, etc., although depending on the process fluid.

The heat medium flow passage in the present invention is not particularly limited as long as the heat medium flows therethrough, and for example, heat exchangers such as heat exchangers, pipes, tanks, pumps, coolers, filters and the like. Related equipment is included. In the present invention, the vapor phase portion in the heat medium flow channel is a vapor phase portion formed in the above equipment, and includes vent lines thereof.

The apparatus of the present invention is an apparatus for detecting an abnormality in a heat exchange process for exchanging heat between a heat medium and a process fluid, which is a heat exchanger for exchanging heat between process fluids, a tank for storing the heat medium, A heat exchanger that heats or cools a heat medium, a pump and piping for circulating the heat medium between the devices, and a heat medium and a leaked process fluid that are provided in a gas phase portion formed in a flow path of the heat medium. It is composed of a gas detector for detecting the gas generated by the contact of.

[0009]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in detail below with reference to the drawings. FIG. 1 is a schematic diagram showing an abnormality detection method of a heat exchange process according to an embodiment of the present invention.

As shown in FIG. 1, in the abnormality detecting method of the present invention, a gas generated when a process fluid leaking in the heat exchanger 1 flows into the heat medium side and the heat medium and the process fluid come into contact with each other. When a component is sent to the heat medium tank 4 through the pipe 3 together with the heat medium, the gas detector 5 provided in the gas phase portion 7 for detecting the gas component promptly detects the leakage of the process fluid. It is a thing.

The heat exchanger 1 is not particularly limited as long as the process fluid and the heat medium exchange heat through a partition wall such as a tube or a flat plate. For example, a multi-tubular cylinder which is a partition wall heat exchanger. Type heat exchangers, plate heat exchangers, spiral heat exchangers, block heat exchangers, etc. can be used. The heat exchanger includes a reactor such as a multi-tube type catalyst-filled reactor that performs heat exchange together with the reaction, in addition to a heat exchanger that simply performs heat exchange.

As the heat medium, as described above,
Molten salt or water is used. As this molten salt,
Both NaNO₂Is a composition containing 20 to 90% by weight of
And a melting point within the range of about 100 to 200 ° C is preferable.
Good NaNO as molten salt ₂, NaNO₃And KN
O₃When using a composition consisting of
20-50% by weight, 5-15% by weight and 45 respectively
More preferably, it is in the range of ~ 65% by weight. Well
NaNO as molten salt₂And KNO₃Composition consisting of
Each of these components is 20 to 9
Those in the range of 0 wt% and 80 to 10 wt%
More preferable. Specifically, for example, NaNO ₂(40 layers
%), NaNO₃(7% by weight), KNO₃(53 weight
%) (Melting point 142 ° C.), NaNO₂(3
4% by weight), NaNO₃(13% by weight), KNO₃(53
Wt%) (melting point: 152 ° C.), NaNO₂
(50% by weight), KNO₃Composition consisting of (50% by weight)
(Melting point 139 ° C.) and the like. Also, these melts
Water is used to lower the freezing point of the molten salt and facilitate temperature control.
You may add and use it.

As the process fluid, when the process fluid flows into the heat medium passage, it produces a gas by coming into contact with the heat medium, and the gas is generated in the gas phase portion in the heat medium passage. The gas is not particularly limited as long as it can be detected.

When the heat medium is the above-mentioned molten salt, the process fluid includes, for example, (a) a substance containing an acidic substance such as HCl, Cl ₂ and H ₂ SO ₄ , (b) a substance containing H ₂ S gas,
(C) Examples include those containing methyl mercaptan gas. When these process fluids come into contact with molten salt, in the case of (a) above, nitrogen oxide gas is generated,
In the case of (b), gases such as nitrogen oxides and CO ₂ are generated,
In the case of (c), dimethyl disulfide, nitrogen oxide, C
Gases such as S ₂ , CH ₄ , H ₂ S are generated.

Hereinafter, when a molten salt is used as the heat medium and the above-mentioned (a) is used as the process fluid, specifically, HCl, Cl ₂ , in the step of producing Cl ₂ by oxidizing HCl, The case where a fluid containing O ₂ or the like is used will be described in detail.

This process fluid is introduced into the heat exchanger 1 through the pipe 2, the reaction progresses in the heat exchanger 1 and the heat is exchanged with the molten salt, and is sent to the next step through the pipe 10.

The molten salt whose temperature has risen by heat exchange with the process fluid is discharged from the heat exchanger 1 and sent to the heat medium tank 4 through the pipe 3. A predetermined amount of molten salt is stored in the heat medium tank 4, and is composed of a liquid phase portion 6 (molten salt) and a gas phase portion 7. The molten salt of the liquid phase portion 6 is sent to the cooler 9 by the pump 8 and cooled,
It is supplied to the heat exchanger 1 again.

In the heat exchanger 1 in the heat exchange process, a crack or the like occurs in the flow path (partition wall) of the process fluid due to stress or corrosion, and the fluid containing HCl, Cl ₂ or the like leaks into the flow path of the molten salt. At times, a reaction as shown in the following chemical formula occurs.

[0019]

[Chemical 1]

[Chemical 2]

[Chemical 3]

As shown in the above chemical formulas 1 to 3, in all cases, the reaction is exothermic, and the number of moles of the gas before and after the reaction is 1 mol to 1.5 mol (chemical formula 1) and 1.125 mol to 1 respectively. This is a dangerous reaction in which the internal pressures of the heat exchanger 1, the piping, the heat medium tank 4, etc. increase from 0.5 mol (chemical formula 2), 0.5 mol to 1 mol (chemical formula 3).

When the above reaction occurs, the nitrogen oxide gas concentration in the gas phase section 7 rises, and the leak of the process fluid is detected early by the gas detector 5 provided in the gas phase section 7. As a result, the interlock operates, the supply of the process fluid and the molten salt into the heat exchanger 1 is stopped, and it is possible to prevent the damage from spreading.

As the gas detector 5, a constant potential electrolysis type or infrared type NOx detector can be used, and specific examples thereof include a constant potential electrolysis type NOx meter manufactured by Shin Cosmos.

The abnormality detection method of the heat exchange process according to the present invention is not limited to the above-mentioned contents, but the heat medium and the process fluid come into contact with each other when the heat medium and the leaked process fluid are mixed. The generated gas component can be used if it can be detected in the gas phase portion in the heat medium flow path. As another mode, specifically, in the heat exchange process in the step of obtaining acrolein by oxidizing propylene, for example, when acrolein in the process fluid leaks, the reaction heat generated by contact with molten salt causes NaNO. Examples include a process in which ₂ is thermally decomposed to generate NOx gas. When the process fluid of (c) above contains methyl mercaptan gas, the contact of these process fluids with the molten salt containing NaNO ₂ causes flammability of dimethyl disulfide, CS ₂ , CH ₄ , H ₂ S, etc. Since gas is generated, the abnormality can also be detected by detecting these combustible gases.

[0024]

EXAMPLES The abnormality detection method of the present invention will be described below with reference to examples, but the present invention is not limited to the following examples.

Reference Example 1 The nitrogen oxide gas and heat generated when the molten salt containing NaNO ₂ and the leaked process fluid containing HCl and Cl ₂ described in the above embodiment were mixed were evaluated.

FIG. 2 shows a schematic view of the entire test apparatus. Figure 2
As shown in FIG.
A constant temperature wall calorimeter (“RADEX-SOLO” manufactured by ASI) 22 for evaluating the risk of mixing with a gas containing l ₂ and absorption bottles 47, 49 for collecting the generated gas are arranged. . In this embodiment, a gas containing HCl and Cl ₂ is continuously supplied and the generated gas is collected. Therefore, the commercially available constant temperature wall calorimeter is improved and the sample supply pipe 52 and the gas are supplied to the sample container 23. The one with the collecting tube 28 attached was used.

In the constant temperature wall calorimeter 22, the supply gas is continuously supplied from the sample supply pipe 52 into the sample container 23 in which molten salt is put in advance, and the gas generated by mixing is covered with the ribbon heater 27. The structure is such that it can be discharged from the gas collection pipe 28. Further, the sample container 23 can be heated by the heater 25 through the jacket 24, and the heat generation and the generated gas at the time of mixing the supply gas and the molten salt 53 can be evaluated under any temperature rising condition or isothermal condition. it can. The temperature of the molten salt 53 is measured by the temperature sensor 26.

Further, a nitrogen cylinder 31 and a hydrogen chloride cylinder 3
2. Chlorine cylinder 33 and oxygen cylinder 34 to valve 3
The supply gas prepared in a predetermined ratio by 8, 39, 40, 41 and the flow meters 35, 36, 37 is supplied from the sample supply pipe 52 to the sample container 23. The oxygen supplied from the oxygen cylinder 34 is supplied to the sample container 23 together with water vapor after being aerated by the ribbon heater 46 after passing through the pure water 45 heated in the constant temperature bath 44.

Using the test apparatus as described above, it is checked whether or not heat is generated when the supply gas and the molten salt 53 are mixed, and the generated gas is mixed with water 48 in absorption bottles 47, 49 and 10% sodium hydroxide. It was collected with an aqueous solution 50. The composition of the obtained collection liquid was analyzed by ion chromatography. The nitrogen oxides are generated by the glass pipe 55 between the gas collection pipe 28 and the absorption bottle 47, and the absorption bottle 4.
It can be confirmed by the coloring (brown) of the gas phase portion in 7, 49.
Further, the rough generation amount of nitrogen oxide can be confirmed by the glass pipe 55 and the color intensity of the gas phase portions in the absorption bottles 47 and 49.

The test was conducted under a temperature rising condition (test 1) and an isothermal condition (test 2), and the composition of the gas supplied to the sample container 23 was set to the ratio shown in Table 1.

[0031]

[Table 1]

<Test 1> As shown in Table 1, the sample container 2
As the gas supplied to No. 3, the gas having the composition 1 is used, and
The test was conducted under a temperature rising condition of 5 ° C./min. At the beginning of the test, only the nitrogen gas was supplied to the sample container 23, and the molten salt 53
When the temperature reached about 70 ° C., the supply of nitrogen gas was stopped and the supply of the composition 1 gas was started. The result of test 1 is shown in FIG.
Shown in.

As shown in FIG. 3, immediately after the supply of the mixed gas was started (when the temperature of the molten salt 53 was about 70 ° C.), heat was generated, and at the same time, a large amount of NOx gas was generated.

<Test 2> As shown in Table 1, the sample container 2
A gas of composition 2 was used as a gas to be supplied to No. 3, and the test was performed under isothermal conditions (heater temperature of 280 ° C.). Then, the gas of composition 3 was switched to perform the test under the same isothermal conditions. The results of test 2 are shown in FIG.

As shown in FIG. 4, heat is generated immediately after the supply of the composition 2 gas is started, and at the same time, a large amount of N 2 is generated.
Ox gas was generated. Further, when switching to the gas of composition 3, heat was similarly generated, and at the same time, NOx gas was generated.

From the results of test 1 and test 2, composition 1,
It was found that the gases of composition 2 and composition 3 generate NOx gas immediately when mixed with the molten salt. The molten salt temperature is about 70 ° C (Test 1: temperature rising condition), about 280 ° C
In (Test 2: Isothermal condition), generation of NOx gas was confirmed. These temperatures are, for example, heat exchange process temperatures (300-350) during the process of producing Cl ₂ by HCl oxidation.
The temperature was lower than (.degree. C.). In the actual heat exchange process (for example, the heat exchange process in the Cl ₂ production step), it is difficult to detect a small amount of leakage due to the temperature change when the leaked process fluid and the molten salt are mixed, but it occurred. If the NOx gas is measured, the leakage of the process fluid can be detected early and quickly.

Reference Example 2 The gas generated when the molten salt containing NaNO ₂ and the leaked process fluid containing H ₂ S were mixed was evaluated.

FIG. 5 shows a schematic view of the entire test apparatus. Figure 5
As shown in FIG. 5, a glass sample container 62 for evaluating the risk of mixing molten salt and H ₂ S gas in a constant temperature bath 61, and a thermocouple for measuring temperature change due to heat generated during mixing. 63 and a supply pipe 64 for supplying H ₂ S gas into the sample container 62. The sample container 62
Is a collection tube 6 for collecting the gas generated by mixing.
Have five. The generated gas is collected by a Tedlar bag (a sampling bag made of a polyfucca vinyl film “Tedlar (registered trademark)” manufactured by DuPont) 66 through a collection pipe 65.

The H ₂ S gas is supplied from the H ₂ S cylinder 67. Between the H ₂ S cylinder 67 and the supply pipe 64,
A draining container 68, a valve 69 for adjusting the gas flow rate, and a gas flow meter 70 are arranged. A thermocouple 71 for measuring the H ₂ S gas temperature is attached to the container 68.

Using the test apparatus as described above, a test was conducted in the following procedure. (1) Molten salt (NaNO ₂ : 40% by weight, NaNO ₃ : 7)
% By weight, KNO ₃ : 53% by weight) and crushed into a sample container 6
A predetermined amount was put in the 2. (2) The sample container 62 was placed in the constant temperature bath 61 and heated to a predetermined temperature. (3) Blow nitrogen gas for purging into the constant temperature bath 61,
The inside of the constant temperature bath 61 was made a nitrogen atmosphere. (4) After the molten salt reached a predetermined temperature, the line through which the gas passed (the line from the pipe 72 to the pipe 73) was replaced with nitrogen gas. (5) H ₂ S gas was supplied into the sample container 62 at a predetermined flow rate. (6) The gas generated by supplying the H ₂ S gas was collected in a so-called Tedlar bag 66 for a predetermined time.

The test results are shown in Table 2.

[0042]

[Table 2]

As shown in Table 2, in Test 6 (for molten salt charging) performed for comparison, no gas other than H ₂ S gas was detected. On the other hand, in tests 3 to 5, N
Gases such as ₂ O, CO ₂ , H ₂ O, NO ₂ , NO and SO ₂ were detected. Especially, since a large amount of nitrogen oxide gas (N ₂ O gas, NO ₂ gas and NO gas) was generated,
It was found that the gas is a detection target gas effective for leak detection in a process including a molten salt containing aNO ₂ and a process fluid containing H ₂ S.

Reference Example 3 This is an evaluation of the gas generated when a molten salt containing NaNO ₂ and a leaked process fluid containing methyl mercaptan gas are mixed.

FIG. 6 shows a schematic view of the entire test apparatus. Figure 6
As shown in FIG. 4, a glass sample container 62 for evaluating the risk of mixing molten salt and methyl mercaptan gas in a constant temperature bath 61, and a thermocouple 63 for measuring a temperature change due to heat generated during mixing. And a supply pipe 64 for supplying the methyl mercaptan gas into the sample container 62. The sample container 62 has a collection tube 65 for collecting the gas generated by the mixing. The generated gas is collected by the Tedlar bag 66 through the collecting pipe 65.

The methyl mercaptan gas is stored in a container 74 containing a methyl mercaptan aqueous solution in a constant temperature circulation tank 7.
It was generated by heating with temperature controlled silicone oil in 5. A container 68 for draining, a valve 69 for adjusting the gas flow rate, and a gas flow meter 70 are arranged between the container 74 and the supply pipe 64. A thermocouple 71 for measuring methyl mercaptan gas temperature is attached to the container 68.

Using the test apparatus as described above, a test was conducted in the following procedure. (1) Molten salt (NaNO ₂ : 40% by weight, NaNO ₃ : 7)
% By weight, KNO ₃ : 53% by weight) and crushed into a sample container 6
A predetermined amount was put in the 2. (2) The sample container 62 was placed in the constant temperature bath 61 and heated to a predetermined temperature. (3) Blow nitrogen gas for purging into the constant temperature bath 61,
The inside of the constant temperature bath 61 was made a nitrogen atmosphere. (4) After the molten salt reached a predetermined temperature, the line through which the gas passed (the line from the pipe 72 to the pipe 73) was replaced with nitrogen gas. (5) Sample container 6 with a predetermined flow rate of methyl mercaptan gas
It was supplied within 2. (6) The gas generated by the methyl mercaptan gas supply was collected in the Tedlar bag 66 for a predetermined time.

The test results are shown in Table 3.

[0049]

[Table 3]

As shown in Table 3, in the test 9 (without molten salt charging) performed for comparison, dimethyl disulfide,
_{CO 2, H 2 S, H} 2 0, methanol, CS ₂ addition of gas was not detected. On the other hand, in Tests 7 and 8, dimethyl disulfide, CO ₂ , N ₂ O, CS ₂ , dimethyl sulfide, CH ₄ , H ₂ S, ethylene, carbonyl sulfide, dimethyl trisulfide, SO ₂ , ethane, H ₂ 0,
Gases such as propylene, isobutene, 1,2-propadiene, methanol, acetonitrile and NO ₂ were detected. Of these evolved gases, dimethyl disulfide and nitrogen oxides (NO
₂ , N ₂ O), CS ₂ , CH ₄ and H ₂ S are effective detection target gases for leak detection in a process consisting of a molten salt containing NaNO ₂ and a process fluid containing methyl mercaptan. .

Example A multitubular catalyst-filled reactor was used as the heat exchanger shown in FIG. 1, and the process gas (process fluid) in the multitubular catalyst-filled reactor was processed in the same manner as in the method shown in FIG. The heat of reaction was removed. The process gas (HCl gas: 1
50 kg / hr, O ₂ gas: 44 kg / hr) was supplied to carry out the oxidation reaction of hydrochloric acid. The heat medium tank 4 holds a heat medium of 340 ° C. (NaNO ₂ : 50% by weight, KNO ₃ : 50% by weight), and the vapor phase part 7 has a potentiostatic electrolysis type NOx.
A detector 5 (manufactured by New Cosmos) is installed. The heat medium in an amount necessary for removing the heat of reaction (exothermic reaction) is sent to the cooler 9 by the pump 8, cooled to 250 ° C. by the cooler 9, and then introduced into the shell side of the reactor 1. Then, the heat of reaction was removed. The process temperature in the reactor 1 was 350 ° C., and the temperature of the heat medium discharged from the shell outlet of the reactor 1 to the pipe 3 was 340 ° C. The process gas at the outlet of the reactor 1 is HCl gas: 23 kg / hour, Cl ₂ gas: 1
24 kg / hour, O ₂ gas: 16 kg / hour, H ₂ O gas: 3
It was 1 kg / hour. In this heat exchange process, if the process gas leaks to the shell side, NaNO ₂ and HC
NOx is generated by the reaction with 1 and / or Cl _2, and this is detected by the NOx detector 5, so that the abnormality can be detected quickly and easily.

[0052]

According to the abnormality detection method of the heat exchange process of the present invention, the gas generated by the contact between the heat medium and the leaked process fluid in the heat exchange process for exchanging heat between the heat medium and the process fluid. By detecting the components, leaks of the process fluid can be detected quickly and easily.

[Brief description of drawings]

FIG. 1 is a schematic view showing an abnormality detection method of a heat exchange process of the present invention.

FIG. 2 is a schematic diagram of a test apparatus used in Reference Example 1 of the present invention.

FIG. 3 is a graph showing the results of calorimetric measurements performed using a constant temperature wall calorimeter in Reference Example 1 of the present invention.

FIG. 4 is a graph showing the results of other calorimetric measurements performed using a constant temperature wall calorimeter in Reference Example 1 of the present invention.

FIG. 5 is a schematic diagram of a test apparatus used in Reference Example 2 of the present invention.

FIG. 6 is a schematic diagram of a test apparatus used in Reference Example 3 of the present invention.

[Explanation of symbols]

1 heat exchanger 2 piping 3 piping 4 Heat medium tank 5 Gas detector 6 Liquid phase part 7 Gas phase 8 pumps 9 cooler 10 piping

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Eisaburo Miyata             Sumitomo Chemical 5-1, Soukai-cho, Niihama-shi, Ehime             Industry Co., Ltd. F term (reference) 2G067 AA34 CC01 DD18 EE08

Claims (5)

[Claims] 1. In a heat exchange process for exchanging heat between a heat medium and a process fluid, a gas component generated by contact between the heat medium and a leaked process fluid is detected in a gas phase portion in a heat medium flow path. A method for detecting an abnormality in a heat exchange process. 2. A gas generated by the heat medium being a molten salt containing sodium nitrite, and the process fluid containing at least one compound selected from the group consisting of chlorine, hydrochloric acid, hydrogen sulfide and methyl mercaptan. The method according to claim 1, wherein the component is nitrogen oxide or a combustible gas. 3. The molten salt contains sodium nitrite in an amount of 20 to
The method according to claim 2, comprising 90% by weight and having a melting point of 100 ° C to 200 ° C. 4. The method according to claim 1, wherein the gas component generated is nitrogen oxide, and this is detected by using a potentiostatic electrolysis NOx meter. 5. A device for detecting an abnormality in a heat exchange process for exchanging heat between a heat medium and a process fluid, the heat exchanger performing heat exchange of the process fluid, a tank storing the heat medium, and heating the heat medium. Or a heat exchanger for cooling, a pump and piping for circulating the heat medium between the devices, and a gas phase portion formed in the flow path of the heat medium, generated by contact between the heat medium and the leaked process fluid A device that detects anomalies in the heat exchange process that consists of a gas detector that detects the gas that is discharged.