DE2444333A1 - OVEN FOR CRACKING HYDROCARBONS TO MAKE OLEFINS - Google Patents

Description

24U333

Dr.-lng. E. BERKENFELD · Dipl.-Ing. H. HEPKENFtLU, patent attorneys, Cologne Attachment file number

for entry of August 21, 1974 VA / Name of d. Note STONE & WEBSTER ENGINEER

ING CORPORATION

Finen furnace for cracking hydrocarbons for the production of oils

The invention relates to a furnace for cracking hydrocarbons to produce olefins; In particular, the invention relates to a process for the thermal cracking of petroleum (petroleum) based feeds to produce olefins. The invention also relates to a method for cracking using a furnace _{β according to the invention}

For thermal cracking ovens are known which have a radiant heat zone and have a convection heating zone; such ovens are often fired by radiant heating burners of very low power. Sometimes there are more than a hundred burners for one oven with a firing capacity of 100 MM SU BTU / h.

The use of many burners is necessary for the furnace design currently in use which requires that most of the heat is transferred to the process liquid by radiation. Such ovens are known, for example, from US Pat. No. 3,487,121.

In the furnace of US Pat. No. 3,487,121, the radiation zone has a beam length of about 4.6 to about 4.9 meters, which results in rapid heat transfer. The radiant heat burners require gaseous fuels and, since they contain excess combustion

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require air, they do not have the thermal efficiency of large-flame burners that burn liquid fuels and even liquid residual fuels, and in many cases with them an almost stoichiometric amount of air can be operated.

Long flame burner fired ovens are illustrated in U.S. Patent 3,677,234. This is what happens with these ovens Fire at atmospheric pressure and the mean beam length is the same size as yellow or greater than that of radiant heating furnaces.

There are also known ovens that use combustion gas under pressure can be operated; these furnaces generally allow the combustion gas and process liquid to be at virtually the same time are at the same pressure so that the pressure differential on the reactor tubes is relieved. The increased pressure on the Combustion side of the stove also makes it easier to use Exhaust, to operate the auxiliary equipment, such as gas turbines. Such a furnace known from US Pat. No. 3,688,494 has a specific one Reaction zone and a certain convection zone, which are connected to each other for the process liquid and the exhaust gas are.

The subject of the present invention is a furnace that can be operated under pressure and a system to generate the thermal energy, those obtained from the high pressure waste gates coming out of the furnace will increase to the maximum.

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The high pressure furnace of the present invention consists of a convection zone with a predominantly convective heat transfer, a short cross-flow zone and a radiation zone with a predominantly Radiant heat transfer. For the sake of simplicity, these zones are referred to as the convection zone and the radiation zone; but this is not to be understood to mean that these zones are limited exclusively to a heat transfer that takes place according to their name are. The furnace process tubes extend immediately from the inlet of the convection zone through the cross-flow zone and through the radiation zone. Long flame burners are arranged both in the radiation zone and in the convection zone. The burner in the radiant zone is located in the center of an inner chimney which is internally designed to have a converging-diverging zone. The combustion gases from the radiant zone go through the interior of the fireplace to it Head and then to the outside of the chimney where the radiant zone process pipes are arranged. The gases then continue to flow via the tubes in the radiation section through the cross-flow zone and finally through the head of the convection zone.

The crack gas quencher * also forms part of the furnace and is preferably ring-shaped to accommodate the process pipes, which practically represent a continuation of the tubes in the radiation zone. Decooled exhaust gas is also used for cooling of the cracked gases in the quencher.

The exhaust gases are used to produce high-pressure steam, to increase the temperature of the hydrocarbon vapor to be processed

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mixed and also for operating a turbine compressor system. After exiting the quencher, some of the exhaust gases are returned to the furnace through the burners.

An embodiment of the invention is described below with reference to the drawing described in more detail; it mean

Figure 1 is an elevational view of the furnace and quencher;

FIG. 2 shows a section according to 2-2 of FIG. 1;

3 shows a section according to 3-3 of FIG. 1;

FIG. 4 shows a section along 4-4 of FIG. 1;

Fig. 5 is a schematic view of a plant for the extraction of Olefin with the furnace of Fig. 1.

FIGS. 1 to 4 show a furnace and a quench cooler for the cracked gas (cracked vapors) and FIG. 5 shows the furnace of the figures T to 4 with the associated system for carrying out the invention Procedure.

As can be seen from FIG. 1, the furnace 2 has a convection zone 4, a radiation zone 6 and a cross-flow zone 8.

The convection zone 4 has a downstream zone 10 and an upstream zone 12 with regard to the exhaust gas flow. The electricity

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downward zone has an inlet 14 for the process liquid, an inlet part 16, a plurality of tubes 18 for the process liquid, a hot gas side 20 and an outlet 22 for the from the Hot gas side 20 outflowing gases. In the downstream zone 10, the tubes 18 for the process liquid are arranged in parallel, and the outer shell 24 is cylindrical to conform to the parallel arrangement of the tubes 18 stand. In practice, the tubes 18 are close to one another in the downstream zone, at a distance from their centers from no more than 16.51 cm and no less than 6.98 cm. The tubes 18 are in the outer concentric circle of the tube assembly no more than 16.51 cm and no less than 6.98 cm from the inner one Surface 26 of the jacket 24 is arranged for pipes with a diameter of 6.35 cm.

The jacket 24 of the upstream zone 12 of the convection zone 4 is angled outwards at an angle of less than 10 ° from the end 28 of the downstream zone 10 to an intermediate point 30, whereupon the jacket is again cylindrical. The downstream zone 10 can optionally be expanded continuously to the cross-flow zone 8 to the outside. The tubes 18 are at an angle of less than 10 ° from the end 28 of the downstream zone 10 to the Cross-flow zone 8 arranged. Practice teaches that tubes of 5fO8 up to 15.24 cm for the convection zone tubes 18 are particularly suitable. For certain applications it may not be desirable the tubes 18, but rather an annular passage in the upstream zone 12 to widen outwards.

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The convection zone 4 also has an additional burner 32 through which fuel, combustion air and in the circuit guided exhaust gas are fed to the convection zone 4. The combustion air has a pressure of 5 to 15 atmospheres, preferably of 10 atmospheres; the exhaust gas has a pressure of 5 to 15 atmospheres, practically 10 atmospheres and a temperature of about 650 ° C. at the outlet 70 of the quencher 62. The mixture of combustion air and exhaust gas is selected so that a pressure of 5 to 15 atmospheres prevail on the combustion side of the furnace 2. Two burners with an output of 50 MM BTU / h are over especially suitable for use as burners 32 and 44.

The cross-flow zone 8 serves to facilitate the flow of the exhaust gas from the jet zone 6 to the convection zone 4 and to the arrangement of the process pipes 18 for the flow of the process liquid from the convection zone 4 to the radiation zone 6. The tubes 18 are in the cross-flow zone 8 by the usual brackets held.

The radiation part 6 has an essentially cylindrical · £ §} Ie 38, an inner chimney 42, a flame burner 44 and a fire-proof roof 46 on top. The chimney 42 has a -eiek-converging outer cylindrical. Surface 48 and forms with the inner wall 50 of the shell 38 an annular passage 52 with changing Cross-sectional area such that the widest annular passage near the upper refractory roof and the narrowest annular opening near the burner 44 is located. The inner surface of the chimney 42 is made up of a downwardly converging part

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54 and an upwardly diverging part 56, the two parts having a central passage 58 for the exhaust gas form; the roof 56 is designed so that the gases are conducted from the central exhaust passage 58 to the passage 52. The converging-diverging design of the chimney 42 promotes gas circulation by pulling the exhaust gas upwards through the inner passage 58 and down through the annular Passage 52 is exercised.

The process tubes 36 extend from the cross-flow zone 8 concentrically through the annular gap 52 and up through the refractory roof 46 which is designed to avoid a pressure drop decrease in circulation. The flame burner 44 is centered in the radiation zone 6 at a height above the inlet 45 of the Chimneys 42, but arranged below the beginning of the diverging part 56. Residual oil, such as bunker or heavy heating oil, Combustion air and circulating exhaust gas are fed through the flame burner 44 into the radiation part 6. The combustion air has a pressure of 45 to 15 atmospheres and the circulated exhaust gas has a pressure of 5 to 15 atmospheres and a temperature of 649 ° C. The mixture of these ingredients is chosen so that the hot side of the furnace has a pressure of 5 to 15 atmospheres.

The quencher 62 is directly above the radiation part 6 arranged. The quencher 62 consists of an outer jacket 64, one Inner wall 66, an inlet 68 and an outlet 70 for the cold side. The inner surface "72 of the outer jacket 64 and the inner

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wall 66 form the cold-side chamber 74 of the quencher 62. The tubes 36 of the radiation zone extend upward through the cold-side chamber 74 to the head portion 60, which is above the quencher 62 is arranged. The preferred coolant for the quencher 62 is recirculated exhaust gas used. After passing through, the exhaust gas passes through the hot side of the various hot systems

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and deiT) additional gas compressor with a temperature of about 260 ° C into the quencher.

The exhaust gas leaves the quencher at temperatures of 593 to 704 ⁰ C; a portion will eventually be returned by the burners 44 and 32 in the furnace "The Rapidquencher 62 causes a Gegenstromkonvektionsaustausch within the annular chamber 74 _a The narrow passage and the high-pressure combustion gas result in a con-

• effective heat transfer coefficient greater than 100 BTU / h / ft F ⁰ . The quenching in the quencher 62 is therefore carried out in less than 50 milliseconds, "preferably in less than 25 milliseconds ₉ "

The composite system of the present invention shown in FIG. 5 has an air compression system 76, a hydrocarbon preheater 78 j, a high pressure ^ steam generating plant 80 and a plant 82 for steam dilution on »

The Lüftkompressionsanlage consists of a turbine 84, an air compressor 86 (first stage) ₉ Luftkompress an EOR 88 (second stage) j a compressor 90 for the cracked gas Lind a combustor 92 _β fuel ;, preferably heavy residual oil is

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passed through line 94 to combustor 92 to drive the gas to win for the turbine 84. The turbine 84 drives the compressors 86, 88 and 90. Atmospheric air is passed through the line 96 is fed to the compressor 86, by which the pressure of the air to 5 to 15 atmospheres, preferably to 10 atmospheres, is increased. The compressed air passes from the compressor 86 through line 98 to the combustor 92 like that Compressor 88. The compressed air is used by the burner 92 to burn the fuel, to drive the turbine and to drive the turbine Compressed air conducted to the compressor 88 can be here to a pressure of 5 to 15 atmospheres, preferably of 10 atmospheres, further compressed and fed through the line 100 ″ to the furnace burners 32 and 40. The exhaust gas from the turbine 84 passes through line 102 into chimney 104,

The plant 80 for the production of high pressure steam consists essentially from an indirect heat exchange pressure vessel 106 and a sump 108 for the high pressure steam, exhaust gas from the furnace is through line 110 of the hot side of the pressure vessel 106 is fed to a temperature of approximately 649 ° C Avoid temperature pressure.

The plant 78 for heating the hydrocarbon feed exists essentially consisting of a preheater 108 and a heat exchanger 111 «The hydrocarbon feed, which initially is heated by the exhaust gas of the turbine 84 in the chimney 104 and steam passes through the line 116 to the cold side of the heater 108, exhaust gas from the steam generating system 80 is through the line

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device 110 passed to the hot side of the heater 108. The temperature of the exhaust gas entering the heater 108 is in the range of a temperature of 538 ° C., specifically at a pressure of about 5 to 15, preferably 10, atmospheres. The feed of hydrocarbon vapor leaves the heater 108 at a temperature of about 393 ° C. and a pressure of 2.67 to 5.06 kg / cm ² absolute 122 receives cracked gas from furnace 2, with the pyrolysis gas from the furnace flowing through the hot side and the hydrocarbon feed and steam flowing through the cold side , 16 to 1.76 kg / cm absolute. The hydrocarbon feed is brought to a temperature of about 538 ° C and passed into furnace 2 through line 116.

The system for generating diluted steam consists of an indirect heat exchanger 124 and an oil heater 126. The indirect Heat exchanger 124 is cracked gas through the Line 128 supplies which the high pressure steam generating vessel 111 at a temperature in the range of 6560 ° C and one Absolute leaves pressure of 1.55 to 2.95 kg / cm. Dowtherm, oil or any other suitable heat transfer fluid is closed through the cold side of the heat exchanger 124 Circuit 130 sent. The heat transfer fluid flows through the hot side of vessel 126 in the heat exchanger with water to form dilution vapor which passes through the conduit 132 of the hydrocarbon feed in line 116

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to be led. The cracked gas leaves the heat exchanger with a temperature of about 232 ° C and a pressure of 1.41 "to 2.81 kg / cm absolute. Through line 122, the cracked gas fed to a quench stream 136 in which the cracked gas quenched and then fed through line 122 to compressor 90 for further processing.

The © exhaust gas from the furnace 2 is in a closed circuit guided through the system. After leaving the furnace 2 through the line 110, the exhaust gas flows through the hot side of the high-pressure steam container 106 and then through the hot side of the hydrocarbon heater 108 to the compressor 140, where it is on a Pressure of about 5 to 15, preferably 10 atmospheres. That the compressor 140 with a temperature of about 260 ° C Exiting exhaust gas then reaches the cold side of the quench cooler 62, where its temperature is reduced to about 649 ° C and the pressure to about 5 to 15, preferably 10 atmospheres, whereupon it passes through the line 142 to the furnace burners 44 and 32. The exhaust pipe 142 is connected to the fuel pipe 94 connected to form the same lines 150 that are in direct communication with the burners 44 and 32.

The interconnected system and burner 2 work as follows:

The hydrocarbon feed at a temperature of first 37.8 ° C and a pressure of 2.81 to 5.27 kg / cm absolute is heated in the chimney 104 to about 316 ° G «dilution steam is at a temperature of about 149 C in the hydrogen

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Cooling line 116 is introduced through which the resulting mixture is fed to the feed heater 108 at a temperature of 288 ° C under a pressure of 2j81 to 5 seconds 27 kg / cm absolute. The temperature of the mixture is increased to 393 ° C. and the pressure to 2.67 to 5.06 kg / cm absolute and fed to the heat exchanger 111, in which the temperature is further increased to 38 ° C. and the pressure to 2.46 to 4 , 92 kg / cm ^{2 is} absolutely hoped for. The mixture of the hydrocarbon feed and the steam is then fed to the convection zone 4 of the furnace 2 at a temperature of 538 ° C. and a pressure of 2.46 to 4 _f 92 kg / cm. The resulting gas leaves the radiation zone 6 of the furnace 2 at a temperature of more than 816 ° C and it is in the quench KIKLeF 62 to a temperature of about 704 ° C and a pressure of 3.16 Ms 1 _S 76 kg / cm absolutely deterred.

The exhaust gas flowing out of the furnace 2 has a temperature of about 649 ° C. and a pressure of 5 to 15 »preferably 10 atmospheres» After air passage through the high-pressure steam vessel 106, the feed preheater 108 and the compressor 140, the exhaust gas has a temperature of 260 ° C and a bridge of 5 to 15 * preferably 10 atmospheres. The exhaust gas is fed to the quench mixer 62 at this brackish and this temperature and flows out of it at a temperature of 649 ° C. and a pressure of 5 to 10, preferably 10 atmospheres. That is the temperature and the crack * at which this Exhaust gas finally reaches the furnace burners 32 iiiici 44 ziarrückge

In the furnace 2, the hydrocarbon vapor mixture passes through

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Furnace pipes to the quench cooler in about 0 * 25 seconds. The combustion gases are in the furnace at a pressure of 10 atmospheres held, and pour through the furnace. The drop in temperature of the combustion gas in the furnace is in the range from 1149 ° C at the burners to 649 ° C at the outlet,

The cracked gas enters the quench heater 62 at a temperature of about 871 ° C. and a pressure of 1.76 to 3 * 16 kg / cm and leaves it after 25 milliseconds at a temperature of 704 ° C. and a pressure of 1 , 76 to 3.16 kg / cm ² absolute. The access

Furnace

composition of the radiation zone 6 of the 2 leaving cracked gas is typical and similar to that disclosed in U.S. Patent 3,487,121.

Claims;

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Claims (17)

Diving. E. BERKENFELD · ■ Dipping. Η «BSRXENFELD. Patent attorney ·, Cologne Attachment file number zur Einsah «from August 21, 1974 VA / Kam. d. Arnn. STOM & IEBSTER ESßHJEER- IHB CORPORATION PATBHTANSPR O _C_H JB H. Furnace for thermal cracking of hydrocarbons, characterized by:
a) a convection zone (4) for a / superatmospheric Pressure,
to) a radiation zone (6) for a / superatmospheric -Be- c) one with the convection zone (4) and the radiation zone (6) opening cross-flow zone d) pipes (18) which go from the inlet (14/16) at one end of the convection zone (4) through the convection zone (4) _f the cross-flow zone (S) and the radiation zone (6), e) at least one long- flame burner (44), f) a chimney (42) arranged in the radiation zone, the Outer wall (48) with the inner wall (50) of the radiation zone an annulus (52) for the passage of those in the distressing zone lying pipes (36), the inner wall (54/56) of the rabbit (42) having a central ivy duct (58) for the combustion gas and this central passage is designed so that it absorbs the combustion gases Mer performs, and g) Means to the de® zeatrisefeen passage (58) of the chimney Incoming fuel gas must be fed into the ling room (52). 509820/0682 ren, from which it flows into the cross-flow zone and the convection zone. 2. Burner according to claim 1, characterized in that it has at least has a burner (32) in the convection zone (4). 3. Burner according to Claims 1 and 2, characterized in that that an annular quench cooler (62) is arranged above the radiation zone at its outlet end, in the annular quench cooler (62) tubes (36) are arranged, the continuations of the tubes (36) lying in the radiation zone, and means for supplying a coolant to the cold side of the quench cooler respectively. 4. Burner according to Claims 1 to 3, characterized in that that the tubes (18) in the convection zone and the tubes (36) in the radiation zone have an inner diameter of 6.35 cm to have, 5. Burner according to Claims 1 to 3, characterized in that that the coolant in the quench cooler is exhaust gas from the furnace (2). 6. Burner according to claim 5 »characterized in that the as Coolant in the quench cooler (52), exhaust gas used a combustion gas with an original temperature of about 1149 ° C and a pressure of about 10 atmospheres in the furnace and leaves the convection zone of the furnace foei a pressure of 10 atmospheres and a temperature of about 649 ° C and E09820 / 0682 ~ ¹⁶ - 244A333 further cooled and compressed again to a temperature of approximately 260 ° C and a pressure of 10 atmospheres before entering the quench. 7 »Furnace according to claim 1, characterized in that the tubes (18) are arranged in the convection zone parallel to a center point and then diverge by an I '/ Inkel of less than about 10 °. 8. Oven according to claims 1 to 7 _9, characterized in that the outer wall (48) of the chimney (42) converges towards one end, so that the annular space (52) has a changing cross section, 9 »Process for the thermal cracking of hydrocarbons for Production of olefins, characterized by the following process steps; a) a hydrocarbon-vapor mixture is fed to the pipes in the convection zone of a furnace ₃ b) the combustion gases in the convection zone are kept at a pressure of about 10 atmospheres, c) the temperature of the hydrocarbon · = · vapor mixture is increased in the convection zone to about 760 ° C and fed to the radiation zone at this temperature ₉ d) Combustion gases with a temperature of about 1149 ° C intended for the radiation zone of the furnace, e) the pressure in the radiation zone is increased to about 10 atmospheres? reu held ,, and K fi θι ο O A / Π f »ο ο f) the hydrocarbon-vapor mixture is heated to about 871 ° C in the radiant zone. 10. The method according to claim 9, characterized by the further Process step that g) the cracked gases by indirect heat exchange with im Circulated exhaust gas cooled to a temperature of about 260 ° C can be quenched. 11. The method according to claim 10, characterized in that the exhaust gases to a temperature of about · 3 & θ 260 ° C by the following Process steps are cooled: h) the exhaust gases are from the convection zone of the furnace in indirect Heat exchange with water leads to the production of high pressure steam, and i) the cooled exhaust gas leaving a high pressure steam generator is in indirect heat exchange with the hydrocarbon-vapor mixture before the entry of the hydrocarbon-vapor mixture fed into the convection zone of the oven. 12. The method according to claim 11, characterized by the further process step that j) the exhaust gas leaving the quench cooler to the furnace burners at a pressure of about 10 atmospheres to enter the Oven is guided. 13. The method «according to claim 9, characterized by the further Process step that the combustion gases in the convection 509820/0682 zone can be initiated by a long flame burner. 14. ' Method according to Claim 11, characterized by the further Process step that the cracked gas in induced heat exchange is performed with the hydrocarbon-vapor mixture to bring the temperature of the hydrocarbon-vapor mixture to about 538 ° C and the hydrocarbon-vapor mixture before its entry into the convection zone of the furnace in one indirect heat exchange has been performed. 15. The method according to claim 14, characterized by the further Process step that for generating steam for the hydrocarbon steam feed the cracked gas in an indirect heat exchange with a heat carrier and then the heat carrier be conducted in indirect heat exchange with water. 16. The method according to claim 12, characterized by the following procedural steps S encryption ί Exhaust gas is fed from a high pressure furnace to a burner, fuel and compressed air are supplied to a burner, a turbine is operated with the gases from the combustor and air compressors are operated by the turbine to be compressed To get air for the kiln burners and the incinerator, and a cracked gas compressor is operated by the turbine, to compress the quenched cracked gas. 509820/0682 24AA333 17. The method according to claim 16, characterized by the further process step that the exhaust gases from the turbine in heat exchange with the hydrocarbon feed. 509820/0682 e e r e i t e