DE2224899A1 - Heat-exchanger - for steam raising in pipes surrounding hot gas pipes fed from an inlet chamber - Google Patents

Abstract

The outer water jackets of the coaxial exchanger elements are fed from a rectangular grid, or circular concentric assembly, of manifold pipes and the hot gas pipes pass through their centres, the hot gas feed to the heat exchange section proper being through extensions of the inner pipes into the inlet chamber. These extensions are either collinear with the inner pipes or converge towards the central axis of the assembly; they are surrounded by a mass of thermal insulation material and may be either channels within that material or be lined with metal tubing jointed to the main inner tubes at one end and to a drilled metal cladding over the insulation at the other. The insulation material is contained within a metal shell flange jointed to the body of the exchanger and carrying the hot gas inlet union. Increased thermal efficiency is achieved due to reduction of heat losses.

Description

Heat exchanger In the usual cracking process, in which naphtha, Gas oil or other hydrocarbon streams at high temperatures in the presence are split by steam to form lower boiling components, it is im generally required to dissipate the heat directly from the process stream, as soon as it leaves the cracking furnace. If the heat is not dissipated immediately, the cracking reaction continues, producing coke and the desired yield Products is reduced. In order to achieve this heat dissipation, one has so far two fundamentally different measures taken. The first method is one direct deterrence with a circulating blood stream. The C) l will be there introduced into the transition line between the oven and the first fractionation column, to dissipate the heat as quickly as possible. In order to recover heat in the process to improve was the quenching technique through an indirect Replaces heat dissipation. Remove the heat exchangers provided in the transition line the heat from the cracked gases by making them high pressure steam for use on others Create a place in the process.

The so-called transition "transition line" heat exchangers are subject coking and often have to be decoked, causing production downtime entry. Failure of the heat exchanger can damage other equipment as well as lead to a loss of production. Their structural design is because of the The high temperatures and pressures that occur here are extremely problematic. A special one The difficult design problem is with the inlet chamber of such a heat exchanger tied together. A heat exchanger with many tubes necessarily has an inlet chamber, which is wider than the transition pipe from the furnace. The inlet chamber creates one sufficient residence time to cause coke formation which clogs the pipes can. Frequent cleaning may be required and premature failure of the pipes due to local overheating can occur. In addition, there occurs the inlet chamber is wider than the transition line, a swirl and a backmixing in some areas of the inlet chamber, which further extends the residence time will. The cracking reaction continues past the optimal point, and you leads to a reduced yield of the desired product. An other species Coking occurs when the cracked gases pass the relatively colder ones Water chambers condense, which leads to the formation of liquid coke. The listed Problems are the reason why the construction of the inlet chamber and the pipe design the transition line heat exchanger is extremely critical. As a failure of everyone the transition line heat exchanger with the steam cracking furnace connected makes an interruption mandatory, a considerable one goes Amount of production lost. It is important to have the longest possible operating time to achieve without failure.

Various prior art American patents, dealing with the problem of the design of transition line heat exchangers, have been granted. U.S. Patents 3,416,598 and 3,414,632 describe the introduction of steam into the inlet chambers to remove the hot reaction gases to displace from the areas in which a backmixing and a swirl occurs. American patent 3,414,632 discloses the introduction of the Steam in a tangential direction, creating a vortex movement along the walls is effected, while the American patent specification 3,416,598 introduces the Steam through two separate circumferential connections at the inlet and at the furthest point the inlet chamber reveals to the areas in which a swirl occurs to be filled in and thus to reduce the residence time, thereby reducing coking and the Loss of yield can be reduced. However, the use of steam causes additional problems Process costs and reduces the heat recovered from the fission gases American patents 3,414,632 and 3,392,211 describe constructions where the heat exchange pipes and water connections are facing downwards extend onto the inlet of the exchanger, thereby reducing the volume of the inlet chamber will. This arrangement has the disadvantage that the water connections are difficult to blow out or to clean accordingly are as a collection point for solids is formed and an early failure occurs due to local overheating can. American Patent 3,392,211 also describes the advantage an increased mass velocity of the fission gases in order to reduce the effects of a to reduce increased dwell time.

A suitable construction of a transfer line heat exchanger Should have the following desirable properties: First, there should be none Steam cleaning may be required, which causes unnecessary hassle and which Operating costs increased. The. Water connections should be arranged so that the Formation of a collecting point for solids is avoided.

In addition, the pipes should be specially protected at the inlet end, so that there is no premature failure due to overheating. aside from that condensation of the fission gases on the water inclusions should be prevented, which leads to an additional coking. Finally, the volume of the inlet chamber should be can be reduced to the smallest possible volume to solve the twofold problems avoid causing the formation of coke and reducing the yield of the desired Product lead.

The invention discloses a construction and arrangement for the Inlet chamber of a transition line heat exchanger, which has the disadvantages of the stand technology, while overcoming the desirable features listed above having.

According to the invention, the residence time of the fission gases in the inlet chamber diminished by putting at the ends of the heat exchanger tubes Extension pieces are arranged. These extension pieces form guide lines with little Volumes extending from the hot gas inlet to the heat exchanger tubes.

The gas velocity is increased, and so is the effective residence time in the inlet chamber is decreased. The extension pieces become complete surrounded by an insulation material that fills the space between the pipes, so that a stagnant area in which coke formation can occur is avoided will. To protect the insulation and keep it in place, as well as to A cover made of a metal alloy prevents the insulation from flowing past attached to the insulation that cuts off with the ends of the extension pieces. Various embodiments of this construction are shown in the drawings and explained in more detail in the subsequent detailed description.

The insulation material fills a large part of the inlet chamber, thereby reducing the residence time and the resulting formation of coke. In addition, the insulation prevents condensation of the fission gases on the water ducts and thus coke formation there. The condensation coke can crumble and the Clog the heat exchanger pipes so that immediate decommissioning is required will.

The pipe extensions decrease the residence time, and it isn't required to arrange the water ducts deep in the inlet chamber. You can be raised so that the guides are blown out through the external water supplies can be, thereby avoiding a build-up of solids leading to a premature failure due to local overheating.

The invention is described below with reference to the accompanying drawings The following shows: FIG. 1 the top view of an embodiment of the invention, in which the Wasserführuxigen in a single plane perpendicular arranged to the axis of the heat exchanger and the pipe extensions are straight Fig. 2 is a vertical section taken substantially along section line 2-2 1, 3 show a second embodiment of the invention, in which the tubes are arranged in a single plane as in Figures 1 and 2, while however the pipe extensions are angled, Fig. 4 shows a third embodiment of the invention, in which the pipes are connected with ring connections, each Guide is arranged at a distance vertically above the next guide, and FIG. 5 shows a cross section along the section line 5-5 of FIG.

The drawings, which are described in more detail here, show two possible ones Embodiments of the inlet chamber of the bypass line heat exchanger, the subject of the present invention. There are also two arrangements of steam generating pipes and the connections are shown.

In Fig. 1 is a plan view of a transfer line heat exchanger shown, the pipe connections are arranged in a plane which is essentially perpendicular to the axis of the heat exchanger. In this illustration, the heat exchanger cut near the inlet to the details of the arrangement of the floor connections to show. In Fig. 1, the water inlet manifolds are 12 with the steam pipe connections 16 connected. The water inlet manifolds 12 are each connected to the blow-out pipes 15, which lead to a blow-out system, not shown to lead. The flange 11, which the bottom cap of the exchanger 26 (Fig. 2) on Main body holds, lies below the level of the manifold. The steam generating pipes 18 extend perpendicularly from the steam pipe connections 16 upwards. The inner tubes 22 conduct the hot fission gases through the exchanger.

This arrangement can be seen more clearly in FIG. The structure of the Inlet chamber of the heat exchanger closes an inlet nozzle 24 with a central one Opening connected to the transition line (not shown) from the inlet of the Dsmpfcrackofens can be connected. The nozzle 24 is attached to the end cover z, on which a flange 10 is located, which is suitably attached to the corresponding Flange 11 is attached to the main exchanger. The inlet chamber is with a Inner lining 30 is provided which forms an intermediate space with the cover plate 26, which is filled with insulation material 28, whereby the volume of the inlet of the The exchanger is reduced and the head is protected from the hot fission gases that enter the rauscher are introduced, is protected. The steam generating pipes are designed as pipe-in-pipe exchangers formed, wherein the steam is generated in the water space from the outer Tube 18 and the inner tube 22 is formed. The inner tube 22 carries the fission gases and is located in the middle of the outer tube 18. The gas flows upwards through the pipe 22 and gives off heat to the water from the manifold 12 through the pipe connections 18 is supplied and thereupon through the annular space 20 between to the Outer pipe 18 and the inner pipe 22 flows upward.

While the heat is transferred via the inner tube 22, the steam is generated the fission gases are effectively quenched within a minimal residence time, thereby interrupting the cracking reaction and any coking reaction that may occur could be limited. Also, the heat transferred to the water is called steam recovered and reinstated in the process. The necessary deterrent the fission gases are thus used to the advantage of the method and thus reduced the cost of the final products. The gas tube 22 extends through the bottom of the connector 16 down to the vicinity of the inner liner 30, thereby reducing the distance which the fission gases between the inlet flange 24 and the tubes 22 must pass through to have. Such pipe extension pieces are in the American patent 3,416,598, it being noted that such a construction to this extent is useless as the hot reaction gases create a dead space between the tubes run through, so that coke is deposited, the deformations and failure of the pipes caused. The patent also states that in the case of heat exchangers with tube sheets, which are the subject of the patent, the extension; pieces of thermal expansion problems can cause in the pipe sheets. However, the present invention fixes the disadvantages pointed out in the prior art patent. To reduce the space between the pipes and avoid overheating, insulation material 28 is placed between the gas pipes 22, creating a conical A protrusion is created which extends downward in the direction of the gas inlet nozzle 24. Close the insulation in order to avoid any gas penetration between the tubes protect and also a hold To create isolation when the end cap 26 is removed, a cover 32 surrounds the insulation 28 and the gas pipes 22, the cover '32 having openings which mate with the ends of the gas pipes 22 cover. The cover 32 is between the inner surfaces the flanges 10 and 11 attached.

The thermal expansion of the extension pieces is compensated by Firstly, you give them a free expansion opportunity on the cover, secondly they are welded to the cover and a change of direction to accommodate the expansion provides or thirdly welds end rings to the cover, which, however, are free can move within the tube 22. On the other hand, the pipe extension pieces also be simple passages that are poured into the insulation material, thus reducing the need for thermal expansion compensation of the pipe extensions unnecessary.

FIG. 3 shows another embodiment of that shown in FIG Arrangement shown in which the water supply lines 16 are again in a single end the horizontal level at the lower end of the heat exchanger. The connector and the arrangement of the tubes is essentially the same as in Fig. 2, wherein Here, however, the cover 26 is considerably reduced and the open area between cover 32 and liner 30 has been minimized. The gas pipes 22 extend through the bottom of the water connections 16, as before described, but instead of straight down, as in Fig. 2, at an angle are arranged so that they are directed towards the central axis of the heat exchanger extend. These pipes were seen - if they were lengthened at one point, which is very close to the inlet flange 24, overlap. At this Arrangement will have a minimum residence time for the fission gases at the inlet of the heat exchanger reached, and the change in direction would help reduce thermal expansion of the Compensate for extension pieces.

In the embodiment shown in Fig. 4, the gas inlet arrangement is essentially the same as that of Fig. 2, so that they are not in detail needs to be described in more detail. Here, however, the manifolds are in place a straight arrangement in a horizontal plane as concentric ring connections 34 formed of different diameters, which with decreasing size in upward Direction are arranged to allow access to each individual port. The advantage of this arrangement is that there are no low points within the water system are formed on darnsich solids can collect. The pipes can be used at this Arrangement can be blown out more effectively than if the formation of the manifold is such that a catchment point is formed.

In Fig. 4, two water manifolds 12 are shown, although more can be used as two. The pipe rejectors 12 feed each of the ring connections 34, which in turn feed the water through the pipes 18 in a manner similar to that described above Way to dispense. No special exhaust manifold is required and everyone the water pipe bend 12 has a blow-out connection 15. The ring connections 34 are through the connecting pipes 36 between the water pipe elbows 12 2 and the Ring closures 34 charged. The mode of operation of the heat exchanger is essentially the same as was described above in connection with FIG. The water flows downwards through the water pipe elbow inwards through the connecting pipes 36 and enters the ring terminals 34. Then it gets up through the space 20 out, in which steam is generated, while the fission gases generated by the Pipes 22 flow to be quenched. Fig. 5 shows a view of a part of Fig. 4 substantially along the section line 5-5 to the arrangement of the ring connections better to illustrate. Here is the connection of the water pipe elbow with the Ring connections 34 can be seen more clearly with the aid of the connecting pipes 36. With 18 designated tubes are distributed around the circumference and extend vertically from the ring connections 34 upwards.

The measures explained on the basis of the described embodiments, namely, reducing the volume of the inlet chamber of the transition line heat exchanger and the arrangement of the manifolds for the steam generating pipes in such a way that that catchment points can of course also be avoided by certain constructive measures Modification of the described embodiments can be achieved without thereby leaves the scope of the invention.

Claims (8)

Patent claims C heat exchangers with hot gas lines by steam generating lines are surrounded, which has a hot gas inlet chamber through which the hot gases can be fed to the hot gas lines, characterized by a) extensions of the Hot gas lines (22), which are used to reduce the distance between the hot gas lines (22) and the inlet nozzle (24) through the hot gas inlet chamber to the vicinity of the Hot gas inlet and b) an insulation (28) extending the Hot gas lines (22) for reducing the volume of the hot gas inlet chamber and the residence time of the hot gases within the hot gas inlet chamber. 2. Heat exchanger according to claim 1, characterized in that the Insulation (28) is bordered by a metal cover (32) which has recesses, which coincide with the ends of the extensions of the hot gas lines (22). 3. Heat exchanger according to claim 1, characterized in that the Extensions of the hot gas lines (22) consist of metal pipes that are attached at the ends the hot gas lines (22) are attached. 4. Heat exchanger according to claim 1, characterized in that the Extensions consist of passages within the insulation (28). 5. Heat exchanger according to claim 1, characterized in that the axis the extensions of the hot gas lines (22) in the axis of the respective hot gas lines (22) and the extensions are just continuations of these additions (2. 6. Heat exchanger according to claim 1, characterized in that the Axes of the extensions of the hot gas lines (22) with the axes of the respective Hot gas lines (22) form an angle and in the direction of the central axis of the heat exchanger are inclined. 7. Heat exchanger according to claim 1, characterized in that the Water can be fed to the heat exchanger pipes (18, 22) from straight pipe connections (16) is, which is substantially in a perpendicular to the axis of the heat exchanger tubes (18, 22) Lie level. 8. Heat exchanger according to claim 1, characterized in that the Water can be fed to the heat exchanger tubes (18, 22) via concentric ring connections (34) is, each in a horizontal plane and in an upward direction with each of decreasing size are arranged one above the other.