EP1318187A1 - Apparatus for cracking a hydrocarbon feed having a high saturates content - Google Patents

Abstract

A steam cracker system, for processing of saturated hydrocarbons, comprises a heat exchanger/reactor ,in which the cracking product is used as heat transfer medium for the transformation reaction of 4-8C (preferably 4-5C) unsaturated hydrocarbons. An apparatus for the cleavage of saturated hydrocarbons comprises a thermal cleavage reactor (especially a cracking oven (2)), feed ports for hydrocarbons and steam, a reaction mixture take-off line leading to a cooler (especially a quench-cooler (5)) and a separator for the mixture. The system also has a feed (12, 30) for mainly unsaturated 4-8C (preferably 4-5C) hydrocarbons leading into a heat exchanger (28) in the low temperature part (preferably 500-750[deg]C) of the oven (2) and/or into a heat exchanger (7, 21), a line (6) leading to this heat exchanger from (5) for the reaction mixture from saturated hydrocarbons to be used as heat transfer medium, another line (6, 6a) for the reaction mixture (optionally from the cooler (5)) to another cooler (preferably a quench cooler (8)) and optionally a line (29) leading to another reactor (20) with catalyst, for the heated, unsaturated hydrocarbons.

Description

The invention has a device for splitting predominantly saturated hydrocarbons with one reactor, especially cracking furnace.

In the chemical industry, especially the plastics industry, are the unsaturated hydrocarbons, in particular with two and three carbon atoms, of particular importance. So-called are used to produce unsaturated hydrocarbons Ethylene plants known. Here, saturated or also unsaturated hydrocarbons common to a cracking furnace supplied with water vapor. The gap temperatures are between 750 ° C and 900 ° C. The ratio of the resulting propylene to ethylene can only be varied within narrow limits. Around To avoid after reactions that lead to losses of ethylene and Lead propylene, the cracked gas is immediately after leaving of the furnace quickly in a so-called quench cooler cooled, which freezes the balance. The cooling takes place at approx. 350 ° C to 650 ° C. At the same time there is waste heat won, for example, for the production of high pressure steam can be used. After the qench cooler there is a further cooling of the cracked gas, which is indirect but also direct by spraying the cracked gas with a heat transfer oil can be. The cracked gas cooled in this way is then fed to a separation plant. One falls into the separation plant heavy residue product by means of pumps for recovery of heat or the temperature control explained above is used as a heat transfer oil.

A method has also become known in which Unsaturated carbons evaporate and together with Steam can be fed to an oven in which the mixture 500 ° C is heated, then with a slightly above atmospheric pressure lie pressure, z. B. 2 bar, a reactor with a catalyst, u. between a zeolite catalyst. Approximately 45% by weight of the unsaturated hydrocarbons are in propylene converted, balance ethylene, propane and ethane. Such System is particularly complex in terms of equipment and also has additional features a particularly large space requirement.

The present invention aims to provide a To create a device that allows using an insert unsaturated hydrocarbons with four to eight carbon atoms to get a high yield of propylene and one has little equipment, and it allows with the direct and / or indirect waste heat from a cracking plant for primarily saturated hydrocarbons to the energy requirement cover.

The inventive device for splitting predominantly saturated hydrocarbons with one reactor, especially cracking furnace, for heating and splitting with a Supply line for the hydrocarbons and steam as well as a discharge line for a reaction mixture in a cooler, in particular Quench cooler, flows and a separation system for that Reaction mixture consists essentially in that a feed line for predominantly unsaturated hydrocarbons with four up to eight carbon atoms, in particular four to five carbon atoms, into a heat exchanger in the low temperature section, in particular with 550 ° C to 750 ° C, the cracking furnace and / or one Heat exchanger opens in which a line for the reaction mixture after the predominantly saturated hydrocarbons flows out of the cooler as a heat transfer medium and for that Reaction mixture after the predominantly saturated hydrocarbons another line, possibly from the cooler, in another cooler, in particular quench cooler, opens and if necessary, a line for the heated, predominantly unsaturated, Hydrocarbons in another reactor Catalyst opens and a separation system for a reaction mixture after the predominantly unsaturated hydrocarbons is provided.

It was quite surprising that the outlet temperature of the cracked gas from the quench cooler is kept so high can be that the waste heat from the same to Heating further use from unsaturated hydrocarbons can be used. After the heat exchanger it will Fission gas cooled again and then fed to a separation plant.

It was also quite surprising that in the low temperature range a cracking furnace has sufficient capacity, up to the use of unsaturated hydrocarbons to be able to heat at a temperature at which they high yield of polypropylene can be implemented. at a system that should have a particularly high capacity, there is also the possibility that the heat cycle of the unsaturated Hydrocarbons are guided so that the waste heat first is taken out of the cooler and the so heated The product then goes further into the low temperature part of the cracking furnace and then fed to the reactor.

If the heat exchanger has a catalyst to split and / or disproportionation and / or dehydrogenation of the hydrocarbons the predominantly unsaturated hydrocarbons on, a particularly simple configuration is given, since none additional reactor is required. Such a heat exchanger can be, for example, a tubular heat exchanger which the catalyst is not in the tubes, but around the same is arranged.

Is the heat exchanger, which is free of catalysts is, via a line for the predominantly unsaturated hydrocarbons connected to another reactor with catalyst, so the regeneration of the catalyst can be done at intervals of a few months due to coke deposition is carried out particularly quickly and effectively, the device of the cracking furnace can also be used.

The supply line for the predominantly unsaturated occurs Hydrocarbons in the heat exchanger and / or others Reactor from another heat exchanger, which is a feeder Derivation for a reaction mixture according to the predominantly has unsaturated hydrocarbons, can also Waste heat recovery after the endothermic conversion of the unsaturated Hydrocarbons.

Is the further heat exchanger with an additional one Heat exchanger via a line for the predominantly unsaturated Connected hydrocarbons, which in turn with a Heat transfer line for a heat transfer medium from the downstream Separation system from the further cooler is connected, so can also the low waste heat from the heat transfer medium for a first one Heating of further use can be used.

If a pipe for steam opens, together if necessary, with the predominantly unsaturated hydrocarbons in the further heat exchanger, so a particularly simple one Waste heat recovery can be realized.

Is for the reaction mixture after the mainly unsaturated Hydrocarbons provided an additional separation plant, so can be particularly advantageous in the dimensions Be taken into account.

In the following the invention with reference to the drawings explained in more detail.

Fig. 1

und 2 zeigen in schematischer Darstellung isotherme Reaktoren,

Fig. 3

in schematischer Darstellung einen adiabatischen Reaktor,

Fig. 4

eine Ausführungsform mit Vielzahl von Kühlern,

Fig. 5

eine Vorrichtung mit einem zusätzlichen Wärme-tauscher im Spaltofen und

Fig. 6

eine weitere Ausführungsform mit einer zweifachen Erhitzung.

Show it:

Fig. 1

and FIG. 2 show a schematic illustration of isothermal reactors,

Fig. 3

a schematic representation of an adiabatic reactor,

Fig. 4

an embodiment with a plurality of coolers,

Fig. 5

a device with an additional heat exchanger in the cracking furnace and

Fig. 6

a further embodiment with a double heating.

The devices were replicated in a laboratory system 1 to 3 and FIGS. 5 and 6, the im The following example results could be achieved.

In Fig. 1, schematically shown device, an insert with 65 wt .-% paraffins, 25 wt .-%, naphthenes and 10.0 wt .-% aromatics comes through the feed line 1 at a temperature of 60 ° C and a pressure of 6 bar in the reactor 2, which is designed as a cracking furnace. In the cracking furnace 2, the mixture is heated up to 760 ° C to 900 ° C. In addition, steam is introduced into the reactor 2 via its own feed line 3 at a temperature of 210 ° C. and a pressure of 5 bar. The weight ratio of insert to steam is 2: 1. The reaction mixture emerging from the reactor 2 reaches the cooler 5 via the discharge line 4 at a temperature of 830 ° and a pressure of 1.8 bar, and is there at 350 ° C. to 620 ° C cooled. The reaction mixture, that is to say the cracked gas, reaches the heat exchanger 7 via the line 6 and serves there as a heat transfer fluid. The reaction mixture then passes via line 6a into further cooler 8 and is cooled there to 220 ° C. and then passes via line 9 into the separation system (not shown) and has the following composition in% by weight: 1 Wt .-% hydrogen 15 Wt .-% methane 25 Wt .-% ethylene 17 Wt .-% butenes 0.5 Wt .-% acetylene 3 Wt .-% butane

Balance olefinic and diolefinic hydrocarbons

The further cooler 8 is a direct cooler and the oil for direct cooling is circulated through the separation system, not shown, and is used to preheat the further use of predominantly unsaturated hydrocarbons supplied via line 22 into the indirectly acting heat exchanger 10, in which the oil is passed through the Line 8a is supplied, u. with the following composition: 70 Wt .-% butenes 30 Wt .-% C ₄ paraffins 100% by weight of the further use are passed together with 100% by weight to 200% by weight of steam via line 23 to the further heat exchanger 11, in which the product mixture from the further use after the reactor 7 transfers the heat to the others Submits. In the heat exchanger 7, the predominantly unsaturated hydrocarbon mixture is reacted in an endothermic reaction and fed to the further heat exchanger 11 via the discharge line 26 and then cooled. The reaction mixture with the following composition: 32 Wt .-% propylene 7 Wt .-% ethylene 31 Wt .-% butenes 30 Wt .-% C ₄ paraffins had a temperature of 250 ° C and the own separation system for separation was supplied via line 24. For the sake of simplicity, it is advisable to install a separation plant that condenses most of the vapor from the mixture from the reactor and then separates the hydrocarbons into a stream that separates the hydrocarbons with three or fewer hydrocarbon atoms from the heavier rest. The light hydrocarbons are fed to another separation plant at a suitable point. The heavy remainder is fed to the cracking furnace.

1 is in the heat exchanger 7, since it also serves as a reactor, a catalyst is arranged, which is built on a zeolitic basis and by the Süd-Chemie company AG Munich can be obtained.

Since both the reactor 2 and the heat exchanger 7 coke after a few months, as in FIGS. 1, 2, 3, 5 and 6 shown, lines 13 for nitrogen, 14 for air and a Electric heater 15 provided. When the system is at a standstill superheated nitrogen and superheated air via valve 16 in the reactors 7, 20 or 21 are introduced, the oxidation products via the valve 16a, the line 18 and corresponding Filters can be released to the environment. about line 17 can the oxidation products from the cracking furnace 2 are derived. The supply lines for the hot air / water vapor mixture to the cracking furnace are for the sake of clarity not shown.

The system shown schematically in Fig. 2 with isothermal reactor essentially corresponds to that of FIG. 1, a Liebig heat exchanger 21 being used instead of the heat exchanger 7 is shown, the greater flow resistance for the Has fission gas and therefore via an ejector 19 with steam is operated, must be suctioned off. The vapor / reaction product mixture then passes through line 25 and line 9 into the separation plant.

The system shown schematically in Fig. 3 with The adiabatic reactor essentially corresponds to the plant 1, but a separate further reactor 20 is provided, in which the catalyst is arranged. The other Reactor 20 is downstream of heat exchanger 7 connected in series via line 29. A regeneration of the Catalyst can be used with such a system, since a small Resistance to interference is easier to carry out. about line 23 becomes steam and line 22 becomes unsaturated Hydrocarbons fed to the further heat exchanger 11.

4 shows a further cracking furnace, wherein a plurality of derivatives 4 in a plurality of coolers 5 flow into a large number of Liebig heat exchangers Empty 21, in which via the supply line 12 for unsaturated Hydrocarbons are heated the same. Via line 27 the cracked gas becomes after the saturated hydrocarbons Separation plant headed.

In the system shown in Fig. 5 is instead of Heat exchanger 7, a heat exchanger 28, u. between in the low temperature zone, of the cracking furnace 2 arranged. In the low temperature zone there is a maximum temperature of 600 ° C, with what temperature the mixture of predominantly unsaturated Hydrocarbons via line 29 in the further reactor 20 arrives.

In the system shown in Fig. 6, the mixture from predominantly unsaturated hydrocarbons via the Line 12 is fed to the heat exchanger 7 and then enters the heat exchanger 28, which is in the lower temperature zone of the Slit furnace is arranged and is then via line 29 with a temperature of 500 ° C introduced into the further reactor 20.

Claims (7)

Device for splitting predominantly saturated hydrocarbons with a reactor, in particular cracking furnace (2), for heating and splitting with a feed line (1, 3) for the hydrocarbons and steam and a discharge line (4) for a reaction mixture, which are in a cooler, in particular Quench cooler (5) opens and a separation system for the reaction mixture, characterized in that a feed line (12, 30) for predominantly unsaturated hydrocarbons with four to eight carbon atoms, in particular four to five carbon atoms, in a heat exchanger (28) in the low-temperature part, in particular with 500 ° C to 750 ° C, the cracking furnace (2) and / or a heat exchanger (7, 21) opens, in which a line (6) for the reaction mixture opens after the predominantly saturated hydrocarbons as a heat carrier from the cooler (5) and for the reaction mixture after the predominantly saturated hydrocarbons, a further line (6, 6a), optionally from the cooler (5) opens into a further cooler, in particular a quench cooler (8), and optionally a line (29) for the heated, predominantly unsaturated, hydrocarbons opens into a further reactor (20) with a catalyst and a separation system for a reaction mixture the predominantly unsaturated hydrocarbons is provided. Device according to claim 1, characterized in that the heat exchanger (7) has a catalyst for splitting and / or disproportionation and / or dehydrogenation of the hydrocarbons of the predominantly unsaturated hydrocarbons. Apparatus according to claim 1, characterized in that the heat exchanger (7) is free of catalysts and is connected to a further reactor (20) with catalyst via a feed line (29) for the predominantly unsaturated hydrocarbons. Apparatus according to claim 1, 2 or 3, characterized in that the feed line (12) for the predominantly unsaturated hydrocarbons in the heat exchanger (7, 21) emerges from a further heat exchanger (11) which feeds and discharges a reaction mixture according to the predominantly has unsaturated hydrocarbons. Device according to one of claims 1 to 4, characterized in that the further heat exchanger (11) is connected to an additional heat exchanger (10) via a line (22) for the predominantly unsaturated hydrocarbons, which in turn is connected to a heat transfer line from the further cooler ( 8) is connected. Device according to one of claims 1 to 5, characterized in that a line (22) for water vapor, optionally together with the predominantly unsaturated hydrocarbons, opens into the further heat exchanger (11). Device according to one of claims 1 to 5, characterized in that an additional separation system is provided for the reaction mixture after the predominantly unsaturated hydrocarbons.

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