JPH08253776A - Method of removing clogging substance from heat exchanger for apparatus for treating waste liquid from cog desulfurization - Google Patents

Abstract

PURPOSE: To remove clogging sulfur by reducing the amount of a gas flowing through a hot bypass to below the amount thereof in an ordinary operation and thus elevating the temp. of a desulfurization waste liquid in a heat exchanger to thereby melt the clogging sulfur. CONSTITUTION: A desulfurization waste liquid discharged from a lower part of an absorption tower in a COG purification process is diluted so that the total calorific value in an apparatus for treating waste liquid from COG desulfurization remains constant, and then mixed with air for oxidation fed through air feed line 22. The mixture is fed to a heat exchanger A and then fed to a lower part 23 of a reaction tower R via heat exchangers B and C. A gas discharged from the top of the tower R is introduced into the heat exchanger C and fed to the exchangers B and A via a line 26 to heat the waste liquid. When the differential pressure in the exchanger B has increased, a hot-bypass valve 30 disposed in a line 29 extending from the line 26 is regulated to reduce the amount of the gas flowing through the hot bypass to below the amount thereof in an ordinary operation to thereby increase the amount of the gas fed to the exchanger B. Thus, the temp. of the waste liquid is elevated to melt the clogging sulfur.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for removing clogging of a heat exchanger for a desulfurization waste liquid treatment apparatus discharged from a COG refining process, and more specifically, a heat exchanger connected and arranged from the waste liquid supply side. In a method for removing clogging of a heat exchanger for a desulfurization waste liquid treatment device from a COG refining process consisting of a subsequent reaction column, melting precipitated sulfur produced in the heat exchanger without performing open washing at the time of clogging The present invention relates to a method for removing the blockage due to the precipitated sulfur.

[0002]

2. Description of the Related Art Coke oven gas obtained from a coke oven, referred to herein as "CO"
"G") contains a large amount of useful components and harmful components such as tar vapor, naphthalene, ammonia, hydrogen sulfide, and cyan compounds. For this reason, the crude gas discharged from each carbonization chamber of the coke oven is subjected to a treatment / operation for separating and recovering those components and detoxifying them by a series of purification steps.
This purification step is carried out in various modes depending on the composition, the quantitative ratio of the components, various conditions, etc.
[Fig. 3] is a schematic diagram for explaining an example of those aspects.

In FIG. 1, a thick solid line (including an arrow) connecting the equipment for various treatments / operations in the upper part shows the flow of COG itself, and the remaining line shows the flow of drainage liquid, by-product, absorption liquid, etc. Is shown. In FIG. 1, COG from the coke oven is cooled from a conduit 1 by a condenser-2 (for example, indirect cooling by seawater) and a direct cooler-3 (for example, direct cooling by gas liquid) to obtain moisture and tar. Is removed,
The effluent discharged from here is separated and collected in a tar / gas liquid decanter-4, and then is thoroughly purified and discharged through, for example, an activated sludge device 6 and a drainage tertiary treatment device 7. In addition, 5 is a tar tank.

On the other hand, the COG is sent to the naphthalene scrubber 9 by the discharger 8, where the naphthalene is removed and recovered, and then introduced into the dry type electrostatic precipitator 11. In the dry type electrostatic precipitator 11, the remaining tar mist is collected. To be removed. In addition, 10 is a naphthalene absorption oil regeneration device from the scrubber-9. Subsequently, the COG is guided to the wet desulfurization unit Z, which is composed of, for example, one or more absorption towers 12 and oxidation towers 13, where the absorption liquid circulated and sprayed from above is used. COG for (desulfurization liquid)
Is introduced from below and brought into countercurrent contact to absorb and remove mainly H ₂ S and HCN in COG.

Next, COG is an ammonia scrubber-1.
Guided to 4. Here, deammonification is performed with sulfuric acid solution.
This ammonia is converted to ammonium sulfate by the ammonium sulfate separation device 15.
The COG itself is collected by the final cooler-1.
Ammonium sulfate, acid mist, etc. that have been cooled and dehydrated in 6
After removing the residual hydrogen, the residual desulfurization is performed in the dry desulfurization tower 17. ₂
S, followed by benzo-rubber scrubber-18
The nozzles are removed and collected. Exit this scrubber-18
COG will be used or required as fuel after that.
It is supplied as a raw material for city gas, etc.
Or convert methane and other hydrocarbons in it into hydrogen,
It is supplied and used as a hydrogen source for the chemical industry. In the figure
19 is a benzene solvent recovery device from the scrubber-18.
Is.

[0006] Of the various refining steps outlined above, the operation of absorbing and removing H ₂ S and HCN in the wet desulfurization unit Z is usually carried out using an alkaline absorbing solution, which is excellent as the absorbing solution. From the catalytic properties, preferably 1,4-
An alkaline absorbing liquid containing ammonium naphthoquinone-2-sulfonate (ammonium naphthoquinone sulfonate) is used. In this case, in the wet desulfurization unit Z, the reactions represented by the following formulas (1) to (6) proceed to take in ammonia in COG, absorb H ₂ S and HCN, and at the same time produce CO ₂ The absorption reaction also progresses.

<Absorption reaction> NH ₃ + H ₂ O → NH ₄ OH (1) NH ₄ OH + H ₂ S → NH ₄ HS + H ₂ O (2) NH ₄ OH + HCN → NH ₄ CN + H ₂ O (3) NH ₄ OH + CO ₂ → (NH ₄ ) HCO ₃ (4) << Oxidation reaction of ammonium hydrosulfide >>

[Chemical 1] <Catalyst oxidation reaction>

[Chemical 2]

Here, by the reaction of the above reaction formula (5), S
(Sulfur) is generated, and this sulfur and NH ₄ HS react with ammonia as shown in the following formula (7) to produce (NH ₄ ) ₂ S _{X + 1.}
Further, this (NH ₄ ) ₂ S _{X + 1} reacts with NH ₄ CN as shown in the following formula (8) to NH ₄ SCN (ammonium rhodanide), which is further produced by this rhodanation reaction (NH ₄ ) ₂ S _X is (NH ₄ ) by the reaction of the following formula (9).
₂ S _{X + 1} is generated. "Polysulfide _{reaction" NH 3 + NH 4 HS +} S X → (NH 4) 2 S X + 1 (7) " rhodanide _{reaction" (NH 4) 2 S X} + 1 + NH 4 CN → (NH 4) ₂ S _X + NH ₄ SCN (8) << Polysulfide regeneration reaction >> (NH ₄ ) ₂ S _X + S → (NH ₄ ) ₂ S _{X + 1} (9)

The desulfurization liquid which has absorbed H ₂ S and HCN in COG and has undergone the reactions (1) to (9) is sent from the bottom of the absorption tower 12 to the oxidation tower 13 where the air for oxidation regeneration is introduced. Where the naphthoquinone sulfonate ammonium catalyst and oxygen in the introduced air further react (NH
₄ ) ₂ SO ₄ , (NH ₄ ) ₂ S ₂ O ₃ , S _X, etc. are generated and sequentially circulated to the upper part of the absorption tower 12, but a part of the desulfurization liquid is discharged from the lower part of the absorption tower 12 (oxidation). Sequential withdrawal (at the front of tower 13). Further, the CO ₂ absorbed in the reaction of (4) is removed by contact with air in the oxidation tower 13 by the reaction of the following formula (10). 2 (NH ₄ ) HCO ₃ → (NH ₄ ) ₂ CO ₃ + H ₂ O + CO ₂ (10)

In the above desulfurization liquid (in the present specification, this desulfurization liquid is appropriately referred to as "waste liquid", "desulfurization waste liquid", "COG desulfurization waste liquid"), NH ₄ SC which is a product of the above-mentioned reactions.
N, (NH ₄ ) ₂ SO ₄ , (NH ₄ ) ₂ SO ₃ , (NH ₄ ) ₂ S
₂ O ₃ , (NH ₄ ) ₂ CO ₃ and sulfur are included. After the desulfurization, the desulfurization liquid is treated by wet oxidation in the desulfurization liquid treatment device 20 to be sulfuric acid and ammonium sulfate, and finally sent to the ammonium sulfate recovery facility 15 to be recovered as ammonium sulfate.

FIG. 2 shows an embodiment of the desulfurization waste liquid treatment apparatus 20. In the case of the embodiment shown in FIG. 2, the desulfurization waste liquid treatment device 20 is composed of a heat exchanger A, a heat exchanger B, a heat exchanger C and a reaction tower R following the heat exchanger A, which are arranged in series from the waste liquid supply side. Although there are three exchangers A to C, the number of heat exchangers is not limited to three as in the embodiment of FIG.
One or two, or four or more can be used, and they can be arranged in parallel instead of in series as shown. Further, the number of the reaction towers R is not limited to one as described above, and may be two or more.

The desulfurization waste liquid extracted from the lower part of the absorption tower 12 is diluted and adjusted so that the total calorific value in the desulfurization waste liquid treatment device 20 becomes constant, and then supplied to the heat exchanger A by the supply conduit 21. However, the oxidizing air is mixed from the air supply conduit 22 on the way. After that, the desulfurization waste liquid is transferred to the heat exchanger A.
Then, it is sequentially supplied to the lower portion 23 of the reaction tower R via the heat exchanger B and the heat exchanger C. On the other hand, the oxidizing gas from the top of the reaction tower R (also referred to as "exhaust gas" in the present specification)
Is introduced into the heat exchanger C (that is, the heat exchanger closest to the reaction tower side) in the direction opposite to the direction of the desulfurization waste liquid by the conduit 25, and then from the conduit 26 to the heat exchanger B and from the conduit 27. It is supplied to the vessel A and the desulfurization waste liquid is heated by the indirect heat exchange in each of the heat exchangers C, B and A.

As mentioned above, NH ₄ SC is contained in the desulfurization waste liquid.
N, (NH ₄ ) ₂ SO ₄ , (NH ₄ ) ₂ SO ₃ , (NH ₄ ) ₂ S
_{In addition to 2} O ₃ , (NH ₄ ) ₂ CO _3, sulfur, and the like, they also contain organic substances suspended in the liquid phase. These components are expressed by the following formulas (11) to ( 14)
Is converted to (NH ₄ ) ₂ SO ₄ and H ₂ SO ₄ . Note that (NH ₄ ) ₂ SO ₄ remains as it is, while organic substances are oxidized. (NH ₄ ) ₂ S ₂ O ₃ + 2O ₂ + H ₂ O → (NH ₄ ) ₂ SO ₄ + H ₂ SO ₄ (11) NH ₄ SCN + 2O ₂ + 2H ₂ O → (NH ₄ ) ₂ SO ₄ + CO ₂ (12) ( NH ₄ ) ₂ CO ₃ + H ₂ SO ₄ → (NH ₄ ) ₂ SO ₄ + H ₂ O + CO ₂ (13) S + 3 / 2O ₂ + H ₂ O → H ₂ SO ₄ (14)

The reactions of the above formulas (11) to (14) are all exothermic reactions, and they are heated to accelerate the reaction. For this heating, the above formulas in the heat exchangers B, C and the reaction tower R are mainly used. The heat generated by the reactions of (11) to (14) is used. For example, in one operation example of this apparatus, the reaction of the formula (11), that is, the oxidation reaction of (NH ₄ ) ₂ S ₂ O ₃ proceeds in the heat exchangers B and C (this oxidation reaction also occurs in the heat exchanger A). The reaction of the formula (12), that is, the oxidation reaction of NH ₄ SCN proceeds in the heat exchanger C and the reaction column R (see FIG. 5A, which will be described later).

Therefore, the heating for promoting the reaction at each of these points utilizes the heat generated by the reaction in the heat exchangers B and C itself and the heat generated by the reaction in the reaction tower R. However, in order to utilize the heat from the reaction in these
Already heated by the heat generated in the reaction tower R by that amount and heated up), the exhaust gas generated in the reaction tower R is supplied from the top to the heat exchanger C through the conduit 25, and thereafter sequentially. Supply to B and A.

In this case, a part of the exhaust gas from the heat exchanger C is bypassed (hot bypass) by the conduit 29 branched from the conduit 26. This hot bypass is for adjusting the reaction temperature in the reaction tower R mainly by adjusting the degree of heating in the heat exchanger B by the exhaust gas, and the adjustment / control is performed by the hot bypass valve 30. Be seen. As shown in the figure, the hot-bypassed exhaust gas is combined with the exhaust gas (conduit 28) from the heat exchanger A.

Further, the hot bypass can be performed on the exhaust gas from the reactor R or the heat exchanger B instead of performing the exhaust gas from the heat exchanger C as described above. Further, in the embodiment of FIG. 2, the heat exchangers A to C are used.
However, when using one heat exchanger, for example, the exhaust gas from the top of the reaction tower is also introduced into the heat exchanger through the conduit in the direction opposite to the direction of the desulfurization waste liquid. However, the hot bypass in this case can be performed by a conduit branched from the conduit.

When the desulfurization waste liquid treatment apparatus 20 is operated as described above, the main control point in the operation is to dilute and adjust the total calorific value of the desulfurization waste liquid treatment apparatus 20 to be constant. (This is directly related to the heat generation amount in the heat exchanger and the reaction tower), the air / waste liquid ratio, that is, the control of the reaction O ₂ ratio to the desulfurization waste liquid, and the hot bypass amount control. The adjustment is performed by adjusting the concentration of the waste liquid.

However, a problem in the operation of this device is that the heat exchanger is clogged by the deposited sulfur during its operation. As shown in the following formula (15), S ₂ O ₃ ^2-
In the above oxidation reaction, sulfur is produced as an intermediate product, and this sulfur is deposited as a solid in the heat exchanger (for example, in the case of the embodiment of FIG. 2, depending on the operating conditions, the heat exchanger A, heat It deposits in both exchanger B and heat exchanger C). 2S ₂ O ₃ ^2- + 1 / 2O ₂ → SO ₄ ^2- + SO ₃ ^2- + 2S (15)

In order to avoid the precipitation of sulfur, it is necessary to operate in the heat exchanger so that the sulfur-producing reaction itself according to the above formula (15) does not occur as much as possible. O ₂ to the desulfurization waste liquid by squeezing the amount
By decreasing the concentration of [for example, by reducing the ratio of air to waste liquid (the ratio to the theoretical amount of air required to oxidize the components in the waste liquid)], thereby increasing the reaction initiation temperature,
For example, control is performed so as to suppress the oxidation reaction of S ₂ O ₃ ^{2− in} the heat exchanger.

FIG. 3 is a schematic diagram for explaining the mode of suppression and control described above. In the figure, the horizontal axis indicates the reaction position from the left, that is, the heat exchanger to the right, that is, from the reactor [. In the case of the embodiment of FIG. 2, this shows the reaction position from the heat exchanger A (left side of the horizontal axis) to the reactor R (right side of the horizontal axis).

As shown in FIG. 3, when the O ₂ concentration is high, the reaction initiation temperature is low, and the generation and precipitation of sulfur start earlier, but this sulfur precipitation is on the left side of the horizontal axis (for example, heat exchanger A
And / or B), and the amount of precipitation increases with the passage of time. Therefore, at this time, if the amount of air from the conduit 22 (in the case of the embodiment of FIG. 2) is reduced, the reaction start temperature rises, but this rising reaction start temperature is the melting temperature of sulfur (119
(C)) to suppress the precipitation of sulfur by eliminating the sulfur production reaction itself on the left side of the horizontal axis (for example, heat exchangers A and B) by reducing the supply air amount so that the temperature exceeds Is.

However, according to the present inventor, the waste liquid treatment apparatus of the above-mentioned mode is actually operated according to the above-mentioned operation mode, and while the control as described above is continued, the differential pressure ( Regarding the supply waste liquid flow, the pressure difference between the inlet and the outlet of the heat exchanger.In the case of Fig. 2, it is observed that the pressure difference between the inlet and the outlet of the heat exchanger B) rises abnormally, and the cause is It was revealed that it was due to the passage blockage due to the sulfur deposited in the heat exchanger.

Therefore, when the cause of the above-mentioned increase of the differential pressure and the production of sulfur in the heat exchanger was further investigated and investigated, the composition ratio itself in the desulfurization waste liquor was changed and was the main component of the desulfurization waste liquor. (NH ₄ ) ₂ S ₂ O ₃ and N
It was found that the ratio of H ₄ SCN was changing. The fluctuation of the composition ratio is due to some factor in the desulfurization unit Z, the process before that, and the operation (the cause of the ratio increase is
Probably due to changes in the properties of the raw coal)
I have to understand that, but it is necessary to take some effective measures anyway.

As a countermeasure, the most primitive method is to stop the entire apparatus each time to open the heat exchanger and wash the deposited sulfur which is the cause of the blockage. After dismantling, cleaning and repairing, not only complicated work such as reassembling is required, but also a new starting operation is required until steady operation, and the thermal efficiency is significantly reduced.

[0026]

Therefore, in the present invention, C
Rise of the above-mentioned differential pressure in the heat exchanger of the OG waste liquid treatment device,
Regarding such a problem due to the precipitation of sulfur, as a method for solving such a defect due to the generation and precipitation of sulfur in this heat exchanger, without stopping the entire system of the apparatus at the time when the differential pressure occurs, By devising the operation itself, the deposited sulfur can be effectively eliminated.

That is, according to the present invention, in removing the blockage of the desulfurization waste liquid from the COG refining process due to the precipitated sulfur in the heat exchanger for the treatment apparatus, the apparatus can be operated from the reaction tower or the final heat exchanger without stopping the entire apparatus. Sulfur blockage by reducing the opening degree of the exhaust gas hot bypass valve beyond the purpose of operating the hot bypass valve in normal operation (= adjusting the reaction temperature in the reaction tower R) (= reducing the hot bypass amount) By dissolving the substance, it is possible to avoid the above-mentioned troublesome washing operation itself, and it is possible to maintain the operation efficiency and the heat efficiency. The blockage removal of the heat exchanger for the waste liquid treatment device from the COG purification step. The purpose is to provide a method.

[0028]

The present invention is directed to supplying desulfurization waste liquor from a COG refining process to one or more heat exchangers and subsequent reaction towers, while the exhaust gas of the reaction towers is sent to the heat exchangers. In the method for removing blockage of a heat exchanger in a COG desulfurization waste liquid treatment apparatus, which is configured to perform hot bypass of a part of exhaust gas from a reaction tower or a heat exchanger while supplying countercurrent, a differential pressure increase in the heat exchanger. At this time, the hot bypass amount of the exhaust gas is made smaller than the hot bypass amount in the normal operation, thereby increasing the temperature of the desulfurization waste liquid in the heat exchanger, thereby melting the sulfur clogging material. Provided is a method for removing clogging of a heat exchanger for a desulfurization waste liquid treatment device.

Although the differential pressure increase in the heat exchanger usually progresses little by little over a long period of time, the "during differential pressure increase" means that the differential pressure increase is detected and then the operation is continued due to the differential pressure increase. It means an appropriate point in time until it becomes impossible, and in this specification, "at the time of increasing the differential pressure" is used in this meaning. Further, the above-mentioned "to make the hot bypass amount of the exhaust gas smaller than the hot bypass amount in the normal operation" means that the hot bypass amount is the original operation purpose, that is, the reaction tower (R in FIG. 2). To reduce the reaction temperature of the heat exchanger, which is usually used for controlling the reaction temperature, and more specifically, for example, by gradually operating the valve in the closing direction (= operating to reduce the opening), It means that the temperature of the waste liquid is operated to exceed the melting point of sulfur (this throttling operation includes fully closing the valve, that is, closing operation).

As an example of the COG desulfurization waste liquid treatment apparatus of the embodiment shown in FIG. 2, the present invention is provided in a hot bypass conduit 29 branched from the conduit 26 when the differential pressure in the heat exchanger B rises. Throttle operation according to the present invention to the hot bypass valve 30 (including: closing operation, the same applies hereinafter)
The hot bypass valve 30 is throttled to increase the amount of exhaust gas supplied to the heat exchanger B, thereby increasing the temperature in the heat exchanger B, thereby increasing the amount of blockage. Certain solid sulfur (precipitated sulfur)
To melt. That is, the hot bypass valve 3
When 0 is reduced, the amount of exhaust gas passing through the heat exchanger B is increased accordingly. By increasing the temperature in the heat exchanger B by this increased exhaust gas and thereby melting the solid sulfur in the heat exchanger B, the blockage due to the solid sulfur can be eliminated.

[0031]

EXAMPLES Examples of the present invention will be described below, but it goes without saying that the present invention is not limited to these examples. FIG.
2 is an example of one actual operation in the apparatus of the embodiment shown in FIG. 2, and Table 1 shows each of the operation examples during normal operation (before temperature raising operation) and during differential pressure increase (when temperature raising operation). It shows a change in temperature balance of a part.

In FIG. 4, the horizontal axis represents time (h), and the vertical axis represents the O ₂ concentration (mol%) in the oxidizing gas, the differential pressure (kg / cm ² ) in the heat exchanger B, and the heat from the bottom. Exchanger A,
The outlet temperatures (temperature of the waste liquid) in B and C are shown. As shown in FIG. 4, when the differential pressure in the heat exchanger B rises (at the time indicated by X in the figure), the hot bypass conduit 2
When the valve 30 provided in No. 9 is throttled beyond the throttling degree in the case of normal operation, the temperature of the heat exchanger B rises (although there is a degree difference, the same applies to the heat exchanger A). The differential pressure of the heat exchanger B temporarily increased, but then dropped sharply and recovered to the normal differential pressure.

[0033]

[Table 1]

At approximately the same time as the decrease in the differential pressure, the O ₂ concentration in the oxidizing gas decreased. This was because the solid sulfur that had been clogged in the heat exchanger melted and began to flow, resulting in a heat exchanger tug. -The flow in the tube improves and the differential pressure decreases, and at the same time, the molten sulfur comes into contact with the air flowing in the heat exchanger tube, and the oxidative decomposition of accumulated sulfur is carried out. This is because a reaction has occurred. At this point, the deposited sulfur, which was involved in the tube blockage in the heat exchanger B, was melted and the blockage was eliminated.

After that, at the time of Y in FIG. 4, the throttle operation of the hot bypass valve 30 according to the present invention was stopped and returned to the original state, and thereafter the state before the temperature raising operation, that is, the normal operation was continued.
In this way, the precipitated sulfur, which is the cause of the blockage of the pipeline, can be dissolved by the squeezing operation of the hot bypass, and the blockage of the sulfur can be extremely effectively removed. Further, as described above, after applying the present invention when the differential pressure increases, the heat exchanger B is opened and inspected in the regular repair of the present device, and as a result, the heat exchanger B is free from any damage such as corrosion and thinning. I was not able to admit.

Further, FIG. 5 shows the heat exchangers A in the case of normal operation and in the case of performing the closing operation of the hot bypass valve 30 as in this embodiment, which is clarified by the heat balance analysis. The relationship between the heat exchange amount and the heat generation amount in B and C and the reaction tower R is shown. Of these, Fig. 5 (a)
Shows a case of normal operation, and FIG. 5 (b) shows a case where the throttle operation of the hot bypass valve according to the present invention is performed (corresponding to one specific operation example of FIG. 4). In addition,
In the figure, "S ₂ O ₃ calorific value" corresponds to the calorific value due to the reaction shown in formula (11), and "SCN calorific value" corresponds to the calorific value due to the reaction shown in formula (12).

As shown in FIG. 5A, during normal operation, the oxidation reaction of (NH ₄ ) ₂ S ₂ O ₃ represented by the above formula (15) proceeds in the heat exchangers B and C (partially It also occurs in exchanger A, but this is small). On the other hand, for example, when the hot bypass valve 30 according to the present invention is throttled when the differential pressure is increased in the heat exchanger B, the oxidation reaction of (NH ₄ ) ₂ S ₂ O ₃ is performed as shown in FIG. 5B. Shifts significantly to heat exchanger A and heat exchanger B.

In the present invention (for example, one operation example of the processing apparatus shown in FIG. 2), as shown in FIG. 4, at an appropriate time after the time when the differential pressure increase occurs in the heat exchangers A to C. Although the throttle operation of the hot bypass valve 30 is performed,
At this time, as shown in FIG. 5B, the oxidation reaction of (NH ₄ ) ₂ S ₂ O ₃ proceeds. However, this oxidation reaction is accompanied by the precipitation of sulfur as shown in the formula (15) and causes the blockage.
Although the hot bypass cannot always be operated in the throttling direction, according to the present invention, when the differential pressure of the heat exchanger rises, the hot bypass throttling operation can be performed to eliminate the blockage due to the precipitated sulfur. It is possible.

[0039]

As described above, according to the blockage removing method of the present invention, when the differential pressure increases due to the deposited sulfur in the heat exchanger for the desulfurization waste liquid treatment apparatus, the apparatus is stopped and the open cleaning is performed. The occlusion can be removed very effectively without performing. Further, the method of the present invention, when the differential pressure of the heat exchanger is increased, by applying each time, it is possible to eliminate the increase of the differential pressure, and further, in the heat exchanger, damage such as corrosion and wall thinning. An excellent effect such as no occurrence is obtained.

[Brief description of drawings]

FIG. 1 is a schematic diagram for explaining an example of a COG purification step.

FIG. 2 is a diagram showing an embodiment of a desulfurization waste liquid treatment apparatus to which the present invention is applied.

FIG. 3 is a schematic diagram for explaining an aspect of removing deposited sulfur in a heat exchanger and a reaction tower subsequent to the heat exchanger.

FIG. 4 is a diagram showing a specific operation example according to the present invention.

FIG. 5 is a diagram showing a relationship between a heat exchange amount and a heat generation amount in each heat exchanger and a reaction tower during normal operation and when a hot bypass valve is closed.

[Explanation of symbols]

 1 COG conduit 2 Condenser 3 Direct cooler 4 Tar gas liquid decanter 9 Naphthalene scrubber 10 Naphthalene absorption oil regenerator 11 Dry electrostatic precipitator Z Wet desulfurization device 12 Absorption tower 13 Oxidation tower 14 Ammonia scrubber 15 Ammonium Sulfate Separator 17 Dry Desulfurization Tower 18 Benzo-L-Scruber 20 Desulfurization Waste Liquid Treatment Device 21 COG Supply Pipeline 22 Air Supply Pipeline 23 Lower part of Reaction Tower R 24-27 Pipeline 29 Hot Bypass 30 Hot Bypass Valve A to C Heat Exchanger R Reaction tower

Claims (2)

[Claims] 1. A desulfurization waste liquor from a COG refining process is supplied to one or more heat exchangers and a reaction tower subsequent thereto, while the exhaust gas of the reaction tower is countercurrently supplied to the heat exchanger and the reaction tower is also supplied. Alternatively, in the method for removing clogging of a heat exchanger in a COG desulfurization waste liquid treatment apparatus which hot-bypasses part of the exhaust gas from the heat exchanger, the hot bypass amount of the exhaust gas when the differential pressure in the heat exchanger rises. Is smaller than the hot bypass amount in the normal operation, and thereby the temperature of the desulfurization waste liquid in the heat exchanger is raised to melt the sulfur blockage, thereby heat exchanger for desulfurization waste liquid treatment device of COG. Blockage removal method. 2. The COG desulfurization waste liquid treatment apparatus comprises three heat exchangers arranged in series and a reaction tower following the heat exchanger, and a part of exhaust gas from the heat exchanger in the immediate vicinity of the reactor side. The method for removing clogging of a heat exchanger for a COG desulfurization waste liquid treatment device according to claim 1, wherein the COG desulfurization waste liquid treatment device is a hot bypass device.