US3682241A

US3682241A - Heat exchanger, particularly for cooling fresh cracked and/or synthesis gases

Info

Publication number: US3682241A
Application number: US14498A
Authority: US
Inventors: Gerhard Clauss; Helmut Herrmann
Original assignee: Schmidtsche Heissdampf GmbH
Current assignee: Schmidtsche Heissdampf GmbH
Priority date: 1969-03-05
Filing date: 1970-02-26
Publication date: 1972-08-08
Anticipated expiration: 1989-08-08
Also published as: JPS4921337B1; GB1305089A; FR2081700A7; DE1911195B2; DE1911195A1

Abstract

A heat exchanger particularly for cooling fresh cracked and/or synthesis gases produced through high pressure and high temperature having a casing with an inlet and outlet for gases. Straight casing pipes closed at their lower ends are located in the casing with centrally located immersion tubes of smaller diameter than the casing pipes for the supply of coolants in the casing pipes. A plurality of pipes forming rows of pipes spaced from one another and a plurality of rows of pipes spaced parallel next to each other are gathered into a nest of pipes. Longitudinal fins connect the casing pipes forming rows of pipes and the casing pipes standing opposite each other of adjacent rows of pipes. The casing pipes of the individual rows of pipes are of such length that their ends form parallel rows to each other aligned perpendicular to the longitudinal axis of the casing pipes. The rows going out from both outer rows toward the center of the nest of pipes gradually rise from pipe row to pipe row. The inlet and outlet side of the nest of pipes are covered with a conical gas inlet and gas outlet head and the length of the casing pipes is such, that a row of pipes in the area of said inlet and outlet heads increase gradually according to the conicity of the heads.

Description

United States Patent Clausset al.'

1541 HEAT EXCHANGER, PARTICULARLY FOR COOLING FRESH CRACKED AND/ORSYNTHESIS GASES Inventors: Gerhard vClauss; Helrnut Herrmann, both of Kassel, Germany A Assignee: Schmidtsche Heissdampf-Gmbl-I,

Kassel-Bettenhausen, Germany Filed: Feb. 26, 1970 Appl. No.: 14,498

, Foreign Application Priority March 5, 1969 Germany ..P l9 11 195.6

US. Cl ..165/ 136, 122/305, 23/277 R,"

References Cited UNITED STATES PATENTS 8/1902 Vicente ..l22/305 '6/1922 2/1967 7/1969 Palchik ..165/ 142 FOREIGN PATENTS OR APPLICATIONS 3/1950 Great Britain.....'., ..165/183 Werner ..l65/l42 f Vollhardt ..165/140 Primary Examiner-Albert W. Davis, Jr. Att0rneyWenderoth, Lind & Ponack ABSTRACT A heat exchanger particularly for cooling fresh I cracked and/or synthesis gases produced through high pressure and high temperature having a casing with an inlet and outlet for gases. Straightcasing pipes closed at their lower ends are located in the casing with centrally located immersion tubes of smaller diameter than the casing pipes for the supply of coolants in the casing pipes. A plurality of pipes forming rows of pipes spaced from one another and a plurality of rows of pipes spaced parallel next to each other are gathered into a nest of pipes. Longitudinal fins connect the casing pipes forming rows of pipes and the casing pipes standing opposite each other of adjacent rows of pipes. The casing pipes of theindividual rows of pipes are of such length that their ends form parallel rows to each other aligned perpendicular to the longitudinal axis of the casing pipes. The rows going out from both outer'rows toward the center of the nest of pipes gradually rise from pipe row to pipe row. The inlet and outlet side of the nest of pipes are covered with a conical gas inlet and gas outlet head and the length of the casing pipes is such, that a row of pipes in the area of said inlet and outlet heads increase gradually according to the conicity of the heads.

7 Clair 1s, 3 Drawing Figures 15] 3,682,241 45] Aug. 8, 1972 United States Patent Clauss et a].

PATENTEU M19 8 I972 SHEET 1 [1F 3 FIG.I

INVENTORS GERHARD CLAUSS HELMUT HERRMANN MW ZMA 4c ATTORNEYS PATENTEDAUG 8 I972 SHEET 2 OF 3 INVENTOIB GERHARD CLAUSS HELMUT HERRMANN v PATENTED AUG 8 I972 SHEET 3 OF 3 m NS ES m L C D R A H R E G HELMUT HERR MANN ZQQWZZ, ,4.d /g

1 HEAT EXCHANGER, PARTICULARLY FOR COOLING FRESH CRACKED AND/OR SYNTHESIS with centrally located immersion tubes of smaller diameter for the supply of coolants, of which a majority form rows of pipes spaced from one another and several rows of pipes spaced parallel next to one another gathered into a nest of pipes.

In order to produce olefins, particularly ethylene, from gaseous or evaporated liquid hydrocarbons, they are subjected to a thermal cracking in a cracking furnace. The cracked gas a mixture of gases which is very reactive and has to be cooled to prevent regeneration.

This requires especially-developed heat exchangers. Such heat exchangers should not only be built to handle high pressure and high temperature, but should also be able to counteract in the heat exchanger as much as possible the regenerating tendency of the cracked gases which means that the undesired precipitation of coke and condenstaion precipitates or other cracked products, in order to avoid as much as possible the soiling of the heating surface which causes an undesirable reduction of the cooling efiect and a smaller production of the desired end product due to said regeneration. With such heat exchangers, attention has also to be given to the cracked gas which flows into the heat exchangers or the process gas obtained from the gasification of the pressure oil so that it does not waste any time entering the cooling, because the time which the gas needs from the moment it enters the heat exchanger until its impact upon the cooling surface, has been proven to be related to the amount of tion of the cracked gas.

Besides, the heat exchanger is supposed to allow a secure control of high thermal stress of the cooling surfaces and it should permit an efficient utilization of the perceptible heat resulting from the gases of the cooling medium through a boiler for the production of energy. I

A number of heat exchangers are known which generally only fulfill partially the above mentioned requirements.

Fire tube heat exchangers are composed of a casing surrounding a water space with tube plates on both ends and the fire tubes which pass through the water space. Such heat exchangers are not very suitable for the cooling of cracked gases, since the tube-plates as well as the casing, due to the cooling wall temperatures which have to be maintained, have to resist a very high pressure of .the boiling coolant of approximately 80-200 gauge pressure measured in atmospheres and therefore requires a casing with strong walls as well as strong tube plates. Therefore, these heat exchangers are very expensive from the point of view of construction and material. Besides, due particularly to a high accumulation of material, at the side of the entry of the heating gas they are very susceptible to the phenomenon of heat accumulation, caused by the high heat supply from the heating gases which leads to the burning of material, particularly of the fire tubes. Such heat exchangers require special precautions, so that the heating agent immediately after entering the gas entry side of the heat exchanger, can without delay or turbulence be grought to act upon the cooling surfaces and can be led to the fire tubes. It is an'object of the invention to avoid such disadvantages.

' There are also known heat exchangers whereby the cooling surfaces are formed by water pipes which are arranged in a casing passed through by heating gases, the casingcan also enclose water pipes provided with longitudinal fins. This kind of heat exchanger is not very suitable for cooling cracked gases, because in the entry area the feed pipes which are set more or less perpendic'ular to the direction of the flow of the heated agent thus reducing its free flow section offers resistance to the cooling agent, which prevents a turbulence free entry of the heated agent into the area of the cooling surface, which unavoidably leads to such delays at the entry side of the heat exchanger, that undesirable regeneration phenomenon takes place. As compared to this known device, the present invention has for an object a construction wherein the casing pipes forming regenerarows of pipes as well as the casing pipes standing opposite each other in adjacent rows of pipes are connected with each other through longitudinal fins and the casing pipes of the individual pipe rows are of such length, that their ends form parallel rows to each other aligned perpendicular to the longitudinal axis of the casing pipes, and these rows starting from both outer pipe rows toward the center of .the nest of pipes rise gradually from pipe row to pipe row.

A further object is to provide a heat exchanger built according to this invention which does not have at the inflow side any built-in objects which interfere with the flow and which could cause turbulence of the heating gases before they flow into the pipe alleys and thus could produce an undesired increase of waiting time, so that the' medium being supplied for cooling can flow without hindrance into the pipe alleys, whereby the waiting period in' the inflow side of the heat exchanger is reduced to a harmless minimum.

A still further object is to provide a construction wherein a harmful localization of heat due to accumulation of material cannot occur, because there do not exist such masses of material. In addition such a heat exchanger due to its special cooling surfaces which consist of so called field pipes, from the point of view of the cooling media and without having an excessive expenditure for material can resist even the highest pressures.

A further object is to achieve a particularly turbulent free inflow of the cracked gas onto the cooling area, that is to say into the pipe alleys, and in order to secure a resistance free outflow of the cracked gas after its cooling, the in and outflow ends of the pipe nest are provided correspondingly with a conical gas inlet and outlet head and the length of the casing pipes of the individual pipe rows is such, that the pipe rows in the area of the conical part of the gas inlet and/or gas outlet head rise gradually according to their conicity.

For the feeding of the cooling agent and the outlet of the mixture of steam the immersion pipes and the casing pipes of the nest of pipes are connected on their upper ends through feeding and runout lines with two distributors located at two opposite sides of the gas butlet head and with the collectors located on the remaining free sides of the gas outlet head. This allows an advantageously compact and uniform construction.

A further object in order to prevent heat losses of the heat exchanger through radiation, to the outside arid in" order to guarantee a free expansion of the pipe nest,

' the distributors and accumulators connected with the pipe nest through feeding and outlet lines are set firmly inla header lined refractorymaterial, which is set on a casing piece lined with thermal insulation which surrounds the center. section of the pipe nest leaving a clearance in between, said casing piece being connected in turn with a foot piece equally lined with thermal insulation where the head-of the gas entrance is located intowhich the lower ends of the casing pipes project.

Since due to the localization of the upper ends of the casing pipes they can expand freely into the gas entrance head according to the thermal stress, the lower 'endsof the casing pipes of the nest of tubes are therefore not connected firmly and tightly with the gas en- Y edge, said plate lying at a distance abovethe footpiece and parallel to the upper foot piece surface, its greatest diameter being smaller than the inside diameter of the lining of the casing and its free edge being sunk into a corresponding recess in the foot piece surface which 2 serves as a sand seal.

A different advantageous construction of the sealing between the free edge of said plate consists in setting into the recess of the foot surface area flexible sealings, onto which the free edge of the side wall of the plate rests.

' heat exchange elements 5 in the so called field pipe 4, It is advantageous if theplate together with the lower pipes with flow favoring casing heads made of a heatresisting material.

With the above and other objects in view which will manner. The cooling agent is fed through the feed pipes 6 which discharge into the upper end of the immersion pipes 3. The steam mixture fonned in theannulus 4 through heating of easing pipes l is led off through the outlet pipe 7 connected onto'the upper end of easing pipe 1. 3

A multiplicity'of casing pipes 1, that 'is to say heat exchange elements 5,standin'g spaced from each other arecombined into a pipe row-,8. Several of these rows of pipes'8 are arranged spaced from each other and parallel to one another,and thus form the nest of pipes 2. Casing pipes l which form rows of pipes 8, that is to space between casing pipes 1. This creates a uniform, cooling'surface impermeable to gases with alleys 10 between the heat exchange elements 5 for the circulation of the thermal agent.

It is understood that the longitudinal fins 9 within the nest of pipes 2 do not need to be welded to each other, they only serve to space and brace the casing pipes among each other. In this case no tight alleys 10 against each other are formed, which actually is not necessary either. These alleys 10, the same as the tight alleys, can be easily cleaned with high pressure jet devices.

At the lower entrance and upper exit end of the nest of pipes 2 there is a conical gas entrance head 11, and/or a gas entrance head 12.-'Ihe casing pipes 1 of the individual row of pipes 8 which project with their ends into the conical part of the gas entrance and/or gas outlet head 11 and 12, are of such length that their ends perpendicular to the longitudinal axis of the casing-pipes l are aligned so that they form parallel rows to each other, and these rows of the nest of pipes 2 increase gradually from one row of pipes 8 to the next row of pipes8. The length of the casing pipes l of the individual row of pipes 8 is chosen in such a manner, that the row of pipes 8 in the conicalarea of the gas entrance and/or gas outlet head 11 and 12 increase gradually corresponding to such conicity.

become apparent from the detailed description below,

. a preferred form of the invention is shown in the drawings in which:

. FIG. 1 shows the heat exchanger in a longitudinalcenter section on the line l--l of FIG. 2,

- FIG. 2 shows the heat exchanger in a cross section on the line 2-2 of FIG. .1, and

FIG. 3 shows the heat exchanger in a longitudinal.

. pipes 1 and immersion pipes 3 are gathered to form The immersion pipes 3 of the heat exchange elements 5 are connected through the feed pipes 6 with are set horizontally next to the gas outlet head 12 on its free side. The steam mixture flowing to accumulators 14 out of the heat exchange elements 5 is led to a steam drum (not shown) for evaporation, from which the steam is taken to supply steam consumers.

In order to avoid heat losses through radiation to the outside and allow a free expansion of the nest of pipes 2, the in and

outflow conduits

6 and 7 together with the distributors 13 and accumulators 14 connected with the nestof pipes 2 are set firmly into a head piece lined with refractory material, said headpiece being set on the central part of the nest of pipes 2 in a casing 16 sursegment of the nest of pipes 2 in casing 16 and the footpart 17 can be sealed gastight, there is set on the lower end of the nest of pipes and connected in a gastight manner with the latter a plate 21 at a certain distance above foot part 17 and parallel to the upper foot plane 19, said plate 21 has around its lateral edge a side wall 20 and its largest diameter is smaller than the inside diameter of the casings lining 16. The free edge 22 of side wall 20 immerses into a recess 23 extending all around the foot plane 19 of the foot part 17 filled with sand to form a sand seal. In order to improve the seal a flexible seal 24 can be set into recesses 23 onto which rests the free edge 22 of side wall 20. In order to obtain, particularly in the lower area of the nest of pipes 2 a good thermal insulation a casing 25 of thermal insulating material is set onto plate 21, which encloses the nest of pipes 2.

So as to protect the lower ends of casing pipes 1 from burning or scaling and in order to achieve an effective distribution of the inflowing gas jet, there are set onto the lower ends of the casing pipes 1 casing hats 26 formed favorably to the flow and made of heat-resisting material.

We claim:

1. Heat exchanger particularly for cooling fresh cracked and/or synthesis gases produced through high pressure and high temperature comprising a casing having an inlet and outlet for gases, straight casing pipes closed at their lower ends in said casing, immersion tubes of smaller diameter than said casing pipes for a supply of coolants centrally located in said casing pipes, a plurality of said pipes forming rows of pipes spaced from one another, said rows of said pipes being parallel and forming a nest of pipes, longitudinal fins (9) connecting said casing pipes (l) forming rows of pipes (8), said casing pipes (1) standing opposite each other in adjacent rows of said pipes, said casing pipes (l) of the individual rows of pipes (8) being of such length that their ends form parallel rows to each other aligned perpendicular to the longitudinal axes of said casing pipes, and said rows extending from both outer rows (8) toward the center of said nest of pipes (2) rising stepwise from pipe row to pipe row said nest of pipes 2 has an inlet and outlet side covered with a conicalgas inlet and gas outlet head (11 and 12) and the length of said casing pipes (l) forming a row of pipes (8) in the area of said inlet and outlet heads increase stepwise according to the conicity ofsaid heads.

2. Heat exchanger according to claim 1 wherein said immersion tubes and said casing pipes are connected at their upper ends by feeding and outlet lines with two distributors located at two opposite sides-of said gas outlethead and with accumulators 14 located on th remaining sides of said gas outlet head.

3. Heat exchanger according to claim 2 wherein said distributors and said accumulators are connected with said nest of pipes through said feeding and outlet lines set firmly in head li ed casing piece lined wr ti'it erm ins atron on w lch sar header is mounted, said casing piece surrounding the center section of said nest of pipes and being spaced therefrom, a foot piece having a recess is lined with thermal insulation to which said casing piece is connected where the inlet of said easing into which the lower ends of said casing pipes project, is located.

4. Heat exchanger according to claim 2, wherein a plate is connected on the lower end of said nest of pipes in a gas tight manner having a side wall on the periphery thereof, said plate lying at a distance above said foot piece parallel to the upper foot piece surface having its greatest diameter smaller than the inside diameter of said casing and said side wall having its free edge immersed into said recess which serves as a sand seal.

5. Heat exchanger according to claim 4, wherein flexible sealings are set into said recess on which the free edge of said side wall (20) rests.

6. Heat exchanger according to claim 5 wherein a casing of thermalinsulating material is installed on said plate surrounding the lower part of said nest of pipes.

7. Heat exchanger according to claim 4 wherein the free lower ends of said casing pipes are provided with flow favoring casing heads made of heat resisting material.

'th re ractory m terial,

Claims

1. Heat exchanger particularly for cooling fresh cracked and/or synthesis gases produced through high pressure and high temperature comprising a casing having an inlet and outlet for gases, straight casing pipes closed at their lower ends in said casing, immersion tubes of smaller diameter than said casing pipes for a supply of coolants centrally located in said casing pipes, a plurality of said pipes forming rows of pipes spaced from one another, said rows of said pipes being parallel and forming a nest of pipes, longitudinal fins (9) connecting said casing pipes (1) forming rows of pipes (8), said casing pipes (1) standing opposite each other in adjacent rows of said pipes, said casing pipes (1) of the individual rows of pipes (8) being of such length that their ends form parallel rows to each other aligned perpendicular to the longitudinal axes of said casing pipes, and said rows extending from both outer rows (8) toward the center of said nest of pipes (2) rising stepwise from pipe row to pipe row said nest of pipes 2 has an inlet and outlet side covered with a conical gas inlet and gas outlet head (11 and 12) and the length of said casing pipes (1) forming a row of pipes (8) in the area of said inlet and outlet heads increase stepwise according to the conicity of said heads.

2. Heat exchanger according to claim 1 wherein said immersion tubes and said casing pipes are connected at their upper ends by feeding and outlet lines with two distributors located at two opposite sides of said gas outlet head and with accumulators 14 located on the remaining sides of said gas outlet head.

3. Heat exchanger according to claim 2 wherein said distributors and said accumulators are connected with said nest of pipes through said feeding and outlet lines set firmly in a header lined with refractory material, a casing piece lined with thermal insulation on which said header is mounted, said casing piece surrounding the center section of said nest of pipes and being spaced therefrom, a foot piece having a recess is lined with thermal insulation to which said casing piece is connected where the inlet of said casing into which the lower ends of said casing pipes project, is located.

6. Heat exchanger according to claim 5 wherein a casing of thermal insulating material is installed on said plate surrounding the lower part of sAid nest of pipes.