JPH0552487A - Decomposed gas quick cooling heat exchanging device - Google Patents

Abstract

PURPOSE:To permit on-line decoking operation within a short period of time by a method wherein a plurality of heat exchanging units are connected directly to the lower part of one set of steam drum so as to be drooped from the lower part of the same to reduce the number of measuring instruments and respective pipelines around the steam drum and obtain a compact constitution as a whole. CONSTITUTION:A plurality of or 10 sets, for example, of heat exchanging units 11 are connected directly to one set of steam drum 1 so as to be drooped from the lower part of the same. A heat transfer tube 6 and a downcomer tube 5, which constitute the heat exchanging unit 11, are fixed to the lower part of the steam drum 1 at only the upper part of the heat exchanging unit 11 while the lower parts of the heat exchanging units are left in free state. According to this constitution, on-line decoking of steam and air is permitted in the heat exchanging units 11. The piping and the control of the pipelines of boiler feed water system are simplified and the number of various measuring instruments and apparatuses around the steam drum can be reduced whereby the system can be simplified. Only one set of steam drum is equipped whereby the whole of the device can be formed compactly, the installation of the title device is facilitated and the cost of installation at site can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cracked gas quenching heat exchanger for quenching cracked gas in a cracking furnace such as petroleum.

[0002]

2. Description of the Related Art In recent years, as a technical trend of cracking furnaces, there is a tendency to shorten the residence time of cracked gas in the reaction tube of the cracking furnace in order to improve the yield of ethylene. As a result, the number of passes in the reaction tube increases. Therefore, it is necessary to simplify the transfer line connecting the cracking coil and the quenching heat exchanger and shorten the cracked gas retention time. As a result,
The number of quenching heat exchangers per cracking furnace will increase.

For such a cracking furnace, a heat exchanger for cracking gas as disclosed in Japanese Patent Publication No. 62-8714 has been proposed. In this proposal, several fins are attached in the radial direction of the heat transfer tube so as to act as a spacer between each adjacent tube and the inner surface of the tube body, and the arrangement of these fins has a rectifying effect on gas. It has a heat transfer effect. Further, these fins narrow the cross-sectional area of the gas passage in the tube body to a required value to increase the gas flow velocity. As a result, coking that adheres and deposits on the heat transfer surface of the coke of the cracked gas is suppressed.

On the other hand, in the conventional heat exchanger for decomposed gas, one steam water drum and one heat exchange unit are integrated, and such a heat exchanger is replaced by a large number of quench heat exchangers. If it is used in a required cracking furnace, the number of steam / water drums will increase, the overall size of the equipment will be reduced, the feed control of the boiler feed water system will be complicated, and the level gauges will be installed in each steam / water drum. There is a problem that the number of instruments and instrumentation such as level control including the above increases, and the number of pipes required around each of these water-water drums increases, which complicates the entire apparatus. there were.

Further, if the coke component in the cracked gas adheres to the heat transfer surface as described above, it impedes heat transfer and increases the pressure loss on the cracked gas side, so it is called decoking at regular intervals. The method requires an operation to remove this deposit, and efficient operation is required to increase the annual operating rate of the ethylene plant or the like and increase the production. However, since such a decoking operation has been conventionally performed by stopping the decomposition furnace and performing water jet cleaning, the operation rate of motion of the plant is reduced.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to directly connect a plurality of heat exchange parts to the lower part of one steam drum so that the number of instruments, instrumentation and pipes around the steam drum is increased. It is an object of the present invention to provide a cracked gas quenching heat exchanger which can be simplified in number, can be formed into a compact structure as a whole, and can be decoking on-line in a short time.

[0007]

That is, the cracked gas quenching heat exchange apparatus of the present invention is constructed by hanging a plurality of horizontally long steam drums and directly connecting a plurality of heat exchange sections, By connecting one steam drum to a plurality of heat exchange parts, the structure around the steam drum can be structurally simplified and a compact structure can be obtained.

Further, by fixing the heat transfer pipe and the downcomer pipe constituting each of the above-mentioned heat exchange parts to the steam drum side at the upper part and making the lower part free, the online decoking becomes possible. This is a preferable configuration for improving the operating rate.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. The cracked gas quenching heat exchanger of the present invention transfers the cracked gas G discharged from the cracking furnace 13 shown in FIG.
In this apparatus, as shown in FIG. 1, a plurality of, for example, 10 as in this embodiment, are hung down to the bottom of one steam drum 1.
The base heat exchange parts 11 are directly connected to each other.

Next, the details of each heat exchange section 11 will be described. As shown in FIG. 3, the heat transfer tube 6 hangs from the lower portion of the steam drum 1 into the tube body section 14. Reference numeral 5 in the figure is a downcomer that hangs down in the heat transfer tube 6, and the cooling water W
Flows down into this and is heated by the high-temperature decomposition gas G to become steam, which rises outside and flows into the steam drum 1.

This steam is separated from the water in the steam drum 1, and the steam is recovered as high-dry steam from the steam outlet nozzle 8 at the upper part of the steam drum 1, while the water descends again in the downcomer pipe 5. , It is naturally circulating.
A boiler feed water feed nozzle is shown at 10 in FIG. Next, the hot decomposed gas G enters through the inlet 4 at the lower end of the tube body 14, rises while applying heat to the heat transfer tube 6, and is discharged through the gas outlet 2 at the upper end of the tube body 14.

A fin (not shown) is attached to the lower half of each heat transfer tube 6 in the lengthwise direction of the tube to form a spacer between the adjacent tube and the inner surface of the tube body 14. Although it can play a role, it is not essential in the present invention to provide these fins. As described in Japanese Patent Publication No. 62-8714, such a fin arrangement has a rectifying effect on the cracked gas G, resulting in an increase in heat transfer effect. Furthermore, the fin naturally transfers heat. By increasing the surface area and appropriately selecting the thickness, the gas passage cross-sectional area in the tube body portion 14 is narrowed to a required value, which serves to increase the gas flow velocity, and as a result, the presence of fins in that portion. The increase of the heat transfer area and the increase of the gas flow velocity bring about a quenching effect on the gas.

In this embodiment, in addition to the gas outlet 2 of the tube body 14, a second gas outlet 3 is provided, which serves as an outlet for heavy oil cracked gas, and the gas outlet 2 is used for light oil cracked gas. It is used as an exit. As described above, the cracked gas quenching heat exchange device of this embodiment is composed of one steam drum 1 and ten heat exchange parts 11 hung and connected to the lower part of the steam drum 1. Each heat exchanging portion 11 is fixed with bolts, and lip seal welding is adopted for the seal portion.

On the other hand, the heat exchange section 11 which is hung and connected to the lower portion of the steam drum 1 moves as the steam drum 1 moves due to thermal expansion during the operation of the apparatus. Heat transfer pipe 6 and downfall pipe 5
Is fixed to the lower part of the steam drum 1 only at the upper part, and is free to the lower part. Therefore, even if any thermal expansion occurs, the heat transfer pipe 6 and the downfall pipe 5
And can absorb thermal expansion without problems.

By having such a structure,
In this heat exchange section 11, online decoking of steam and air is possible. In this case, online decoking is to remove coke by burning mixed gas of steam and air heated to about 650 ° C. You can, but at this time, steam drum 1
The high-pressure water inside is completely blown, the steam drum 1 is filled with steam, and the wall temperature of the heat transfer tube 6 is raised. Therefore, the combustion effect of coke is enhanced, and coke can be completely removed in a short time. ..

Such a system based on online decoking enables complete automation of the plant and can increase the operating rate of the plant.

[0017]

As described above, according to the cracked gas quenching heat exchange device of the present invention, the piping of the boiler water supply system and its control are simplified, and various instruments and instruments around the steam drum and those are provided. Since the number of pipes etc. is reduced and it is simplified and only one steam drum is provided, the whole device can be made compact, and as a result, installation is easy and installation cost can be reduced locally. It has many effects.

Further, since the heat exchange section applied to the apparatus of the present invention is capable of on-line decoking, it is possible to improve the operating rate of the plant and reduce the worker cost, and to promote the automation of the plant. There is also an advantage that it can be measured.

[Brief description of drawings]

FIG. 1 is a side view of a cracked gas quenching heat exchange device according to the present invention.

FIG. 2 is a front view showing a state in which the apparatus of FIG. 1 is assembled in a decomposition furnace.

FIG. 3 is an enlarged front cross-sectional view of a heat exchange section constituting the device of FIG. 1 Steam Drum 5 Precipitation Tube 6 Heat Transfer Tube 11 Heat Exchange Section 14 Tube Body G Decomposition Gas

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yu Kitayama, 3 Chikusaigan, Ichihara, Chiba Mitsui Oil Chemicals Co., Ltd. Incorporated (72) Inventor Masahiko Yoshida 3 Chikusaigan, Ichihara-shi, Chiba Mitsui Petrochemical Industry Co., Ltd.

Claims (2)

[Claims] 1. A cracked gas quenching heat exchange device having a plurality of heat exchange portions directly connected to a lower portion of one steam drum. 2. A heat transfer tube and a downcomer tube of each heat exchange section that hang down from the bottom of one steam drum are fixed to the steam drum side at the upper part, and the lower part is free.
The decomposed gas quenching heat exchanger described.