JPH05223495A - Adhered substance removing method of ammonia water heat exchanger - Google Patents

Abstract

PURPOSE:To provide the method of removing adhered substances in a short period of time without dismantling the ammonia water heat exchanger in the refining system of coke furnace gas. CONSTITUTION:A T-tube 52 at the inlet side of ammonia water for an ammonia water heat exchanger 40 is connected to a tank 59 receiving benzole absorbing oil by a rubber hose 57 through a circulating pump 56. One end of another rubber hose 58 is connected to another T-tube 55 at the outlet side of the ammonia water and the other end of the hose 58 is inserted into the tank 59. The circulating pump 56 is started to circulate the benzole absorbing oil through the ammonia water flow passage of the ammonia water heat exchanger. When the circulation of the benzole absorbing oil is continued for three days, adhered substances (oil content, pitch and naphthalene) can be removed cleanly. According to this method, the adhered substance can be removed within a short period of time without dismantling the ammonia water heat exchanger whereby the recovering rate of NH3 can be improved.

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 deposits on a heat exchanger used for cooling ammonium water used for absorbing and removing ammonia in a coke oven gas refining system.

[0002]

2. Description of the Related Art Coke oven gas (generally called C gas) generated from a coke oven is used for recovering and removing NH ₃ and naphthalene in C gas in a gas refining process. FIG. 9 is a diagram showing a purification process of C gas. Gas 1 generated from the furnace is sprayed with ammonium hydroxide 3 in an ascending pipe 2 and cooled to about 800 ° C to about 80 ° C. The tar and the noble water 3 are discharged to the decanter 5 before the primary cooler 4, where the tar is separated and removed from the noble water, and the noble water 2 is used again for gas cooling.

The gas (about 34 ° C.) cooled by the primary cooler 4 is pressure-fed to the final cooler 7 by the blower 6 and is again cooled by water spraying. The cooled gas passes through the detarer 8 (which removes tar remaining in the gas) and enters the ammonia scrubber 9. In addition, the gas may be directly sent from the final cooler 7 to the ammonia scrubber 9 without providing the detara 8. In the ammonia scrubber 9, the cheap water is sprinkled, and NH _{3 in} the gas is
90% is absorbed and removed by annoying water. The remaining NH ₃ is completely absorbed and removed in the next saturator 10 by spraying a sulfuric acid solution.

The low temperature of the ammonium hydroxide used in the ammonia scrubber 9 has a higher NH ₃ absorption efficiency. on the other hand,
The cheap water sent to the ammonia scrubber 9 is 70
Since it is a high temperature of ~ 75 ℃, 3 in the heat exchanger 40 before watering.
The absorption efficiency of NH ₃ is increased by cooling to 0 to 34 ° C.

The heat exchanger for cooling the noble water is shown in FIGS.
A plate heat exchanger as shown in is used. The plate heat exchanger 40 has a plurality of heat transfer plates 41 formed in a corrugated shape as shown in FIGS. It is formed on the front and back of the heat transfer plate 41 to allow countercurrent heat exchange. Ansui enters from the inlet pipe 44 formed in the inlet header and the outlet pipe 4 formed in the outlet header.
5, the cooling water enters through the inlet pipe 46 formed in the outlet header and is discharged through the outlet pipe 47 formed in the inlet header.

When the plate heat exchanger is used for a long period of time, deposits adhere to and increase on the low water flow passage side and the cooling water flow passage side of the heat transfer plate 41, and the overall heat transfer coefficient (U value and U value) of the heat transfer plate 41 increases. (Abbreviated) decreases, the temperature of the low water supplied to the ammonia scrubber rises, and the NH ₃ absorption efficiency largely decreases. The deposits on the heat transfer plate are
Pitch and naphthalene, cooling water side is scale and sludge. In order to prevent the rise of the temperature of the cold water supplied to the ammonia scrubber, after about 9 months of use, the equipment is shut down, the plate heat exchanger is dismantled, and high-pressure water jet injection is used for cleaning and removal.

The following patent documents have been published as methods for removing deposits on boilers and heat exchangers. (1) A method in which a high-pressure jet spray with clean water for cleaning and a spray of a specific cleaning liquid are used together to remove deposits (JP-A-52-92003). (2) A method in which a jet stream of a water lance moving by a jet stream moving device is pulsed by a jet stream interrupting device to remove adhering substances by the pulse jet stream (Japanese Patent Laid-Open No. 58-117999).

[0008]

The method of disassembling the plate heat exchanger and jet-washing it with high-pressure water has a problem that it takes 6 days to wash and the cost is high.
The method disclosed in Japanese Patent Application Laid-Open No. 52-92003 also has to be carried out by disassembling the plate heat exchanger, and has the same problems as described above.

The method disclosed in Japanese Patent Laid-Open No. 58-117999 can be applied to a heat transfer tube of a boiler having a relatively simple flow path with a heat transfer tube having an inner diameter into which a water lance can be inserted, for example, a plate heat exchanger. It cannot be applied to small and complicated flow passages such as.

It is an object of the present invention to provide a method for removing deposits in a short period of time without disassembling the low water heat exchanger.

[0011]

DISCLOSURE OF THE INVENTION The present invention is intended to achieve the above-mentioned object, and one of them is to use the heat used for cooling the noble water of the gas purification system of the coke oven gas. In the method for removing deposits on an exchanger, the deposits on the flow path of the anhydrous water are washed and removed by circulating benzene absorption oil.

The other one is a method of removing deposits of a heat exchanger used for cooling the cheap water of a gas purification system for coke oven gas, in which a benzol absorption oil is circulated in the flow path of the poor water. A method for removing deposits of an anhydrous heat exchanger, characterized in that an acid solution is circulated in the coolant channel to wash and remove deposits in the channel.

[0013]

[Function] Since the oil, pitch and naphthalene which are the deposits on the water transfer side of the heat transfer plate are soluble in the benzol absorption oil, the deposits are dissolved and removed by circulating the benzol absorption oil in the water transfer passage. be able to.

Since the scale and sludge which are the deposits on the cooling water channel side are dissolved in an acid solution (for example, hydrochloric acid solution), the deposits can be dissolved and removed by circulating the acid solution in the cooling water channel. .. Therefore, it is not necessary to dismantle the plate heat exchanger since it is sufficient to circulate the benzol absorption oil in the low water channel and the hydrochloric acid solution in the cooling water channel.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 8 is a system explanatory view of an ammonia scrubber provided with a plate heat exchanger according to the present invention. In the figure, the cheap water stored in the cheap water tank 10 (70 to 75 ° C)
Is sent to the plate heat exchanger 40 through the pipes 12 and 13 by the cheap water pump 11 and exchanges heat with the cooling water for 30
Cool to ~ 34 ° C. After that, the cheap water reaches the branch pipe 15 through the pipe 14, and is branched into the pipe 16 on the ammonia scrubber 9a side and the pipe 17 on the ammonia scrubber 9b side.

Hereinafter, since the flow path of the cheap water is the same in the ammonia scrubbers 9a and 9b, only the ammonia scrubber 9a will be described. The branched off water is sprayed through the pipe 16 to the gas rising from the upper spray 18 to the lower chamber 21 to the upper chamber 19. Also, the lower chamber 21
Low water is sprayed from the lower spray 20 to the incoming gas. That is, the gas that has entered the ammonia scrubber 9a, after being absorbed NH ₃ by ammonia liquor to be sprayed in the lower chamber 21, it is absorbed NH ₃ again by ammonia liquor to be sprayed in the upper chamber 19.

A part of the ammonium hydroxide in the upper chamber 19 and the lower chamber, which has absorbed NH ₃ in the gas, is sent to the lower spray 20 through the pipes 22 and 23 by the circulation pump 24 and the pipe 25 to be sprayed. The increased amount of ammonium water accumulated at the bottoms of the ammonia scrubbers 9a and 9b overflows into the ammonium-containing water tank 27 through the pipe 26, and then is fed and processed by an ammonia stripper charging pump 28 to an ammonia stripper (not shown).

Water is sent to the plate heat exchanger 40,
The cooling water that has exchanged heat with the cheap water is passed through the pipe 29 to the cooling tower 3
Water is sent to 0. The cooling water cooled in the cooling tower 30 is pressure-fed by the cooling water pump 31 to the plate heat exchanger 40 through the pipe 32, and is used again for cooling the cheap water.

A method of removing the deposits on the heat transfer plate of the plate heat exchanger used as described above will be described below.
The deposits on the side of the low-water channel are removed as shown in FIG.
In the figure, a T-shaped pipe 52 having a valve 51 connected thereto is attached to the low-water inlet side pipe 50 of the plate heat exchanger 40, and a T-shaped pipe 55 having a valve 54 connected to the low-water outlet side pipe 53 is attached. A rubber hose connects the T-shaped pipe 52 on the side of the low water inlet and the discharge pipe of the circulation pump 56. On the other hand, one end of a rubber hose 58 is connected to the T-shaped tube 55 on the side of the low water outlet, and the other end is inserted into a tank 59 containing benzol absorbing oil.

Next, the facility is shut down, and the low water inlet side pipe 50 is installed.
The valve 60 and the valve 61 of the low water outlet side pipe 53 are closed.
The valves 51 and 54 are opened, and the circulation pump 56 is activated to circulate the benzole absorbing oil through the low water flow path of the plate heat exchanger 40. Circulation with this benzol absorbing oil,
If the washing is continued for 3 days, the deposits (oil, pitch and naphthalene) on the low-water channel are removed cleanly. In addition,
As the benzol absorbing oil used for removing the deposits, the one obtained in the C gas benzole recovery system is used.

To remove the adherence on the cooling water flow path side, after stopping the equipment, as shown in FIG. 2, a hydrochloric acid solution (hydrochloric acid concentration 10%)
An acid resistant hose 72 is provided between the tank 70 containing the water and the cooling water inlet pipe 46 of the plate heat exchanger 40 via a circulation pump 71.
Connect with. On the other hand, one end of the acid resistant hose 73 is connected to the cooling water outlet pipe 47 of the plate heat exchanger 40, and the other end is connected to the tank 70.
Insert it in. The circulation pump 71 is activated to circulate the hydrochloric acid solution through the cooling water passage of the plate heat exchanger 40. If the circulation and washing with the hydrochloric acid solution are continued for about 8 hours, the deposits (scale and sludge) on the cooling water passage can be removed cleanly.

In FIG. 10, cleaning of the low water channel with benzol absorbent oil was performed once / February, and cleaning of the cooling water channel with acid solution and cleaning of the low water channel with benzol absorbent oil were performed once / year. It is a graph which showed transition of overall heat transfer coefficient (U) Kcal / m ² h of a heat transfer plate at this time. With this cleaning method, the overall heat transfer coefficient of the heat transfer plate is 400 Kcal.
It was possible to maintain the temperature above / m ² h ℃.

Table 1 shows the specifications when the method of the present invention is carried out and when the conventional method is carried out at the above proportions. By carrying out the method of the present invention, the NH ₃ recovery rate of the ammonia scrubber is improved by 6%, the sulfuric acid usage of the saturator can be reduced by 3.2 t / d, and the crude gas oil recovery is 0.75 t. / D increased.

[0024]

[Table 1]

Although the above embodiments have been described with respect to the plate heat exchanger, the method of the present invention can be applied to the removal of deposits on a multi-tube heat exchanger.

[0026]

Since the present invention is constructed as described above, the following effects can be obtained. (1) Adhesion can be removed without disassembling the heat exchanger. (2) The deposit can be removed in a shorter period of time than the conventional method, and the removal cost can be significantly reduced. (3) By improving the NH ₃ recovery rate, the amount of sulfuric acid used in the downstream process can be reduced, and the amount of crude light oil recovered can be increased.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a method for removing deposits from a low-water channel according to the present invention.

FIG. 2 is an explanatory diagram of a method for removing deposits on a cooling water channel according to the present invention.

FIG. 3 is a plan view of a plate heat exchanger.

FIG. 4 is a front view of a plate heat exchanger.

FIG. 5 is a diagram showing a state of attachment of deposits on a heat transfer plate.

FIG. 6 is a front view of a heat transfer plate.

FIG. 7 is a view showing a corrugated cross section of a heat transfer plate.

FIG. 8 is an explanatory diagram of a system of an ammonia scrubber provided with a plate heat exchanger.

FIG. 9 is a process diagram for purifying C gas.

FIG. 10 is a transition graph of the overall heat transfer coefficient of the heat transfer plate when the method of the present invention is carried out.

[Explanation of symbols]

 40 plate type heat exchanger 46 cooling water inlet pipe 47 cooling water outlet pipe 52 T pipe 55 T pipe 56 circulation pump 57 rubber hose 58 rubber hose 59 tank 70 tank 71 circulation pump 72 acid resistant hose 73 acid resistant hose

Front Page Continuation (72) Inventor Hiroshi Nagano Marunouchi 1-2-2 Marunouchi, Chiyoda-ku, Tokyo Nihon Kogyo Co., Ltd. (72) Inventor Kenji Inada Marunouchi 1-2-2 Marunouchi, Chiyoda-ku, Tokyo In the company

Claims (2)

[Claims] 1. A method for removing deposits of a heat exchanger used for cooling of deposits of coke oven gas, such as cooling of deposits, wherein a deposit of benzole is circulated through deposits in the passage of deposits of deposits. A method for removing deposits from an anhydrous heat exchanger, which comprises cleaning and removing. 2. A method for removing deposits of a heat exchanger used for cooling cold water in a gas purification system for coke oven gas, wherein benzene absorption oil is circulated in a flow path of cold water to cool water. A method for removing deposits of an ammonium hydroxide heat exchanger, which comprises washing and removing deposits in the flow channel by circulating an acid solution in the flow channel.