EA042704B1 - METHOD FOR OBTAINING ETHYLENE AND CHEMICAL COMPLEX FOR OBTAINING ETHYLENE - Google Patents

Description

Technical field

This invention relates to a process for producing ethylene from ethane, as well as to a chemical complex suitable for such a process for producing ethylene.

State of the art

A known method for producing ethylene from ethane by steam cracking of an ethane stream under the action of heat to obtain a product stream containing ethylene and hydrogen. Before any subsequent step in which ethylene is further processed into valuable chemical intermediates, the product stream containing ethylene must be purified. In addition to ethylene and hydrogen, the product stream from the steam cracker may also contain acetylene and unreacted ethane. In addition, said product stream may contain some carbon monoxide and carbon dioxide as impurities. Carbon dioxide can be formed in the presence of oxygen (due to the introduction of a small amount of air into the steam cracker) and/or in reactions of the conversion of hydrocarbons with steam. In addition, carbon monoxide and carbon dioxide may be present as impurities in the feedstock. Moreover, said product stream may contain methane and C3+ hydrocarbons, and these impurities may be formed during the steam cracking of ethane, which is usually a non-catalytic, non-selective conversion process. The latter of these impurities may also come from the ethane feed stream. All components other than ethylene must be removed from the product stream as they may interfere with any subsequent step in the further processing of ethylene.

Typically, carbon dioxide is removed from the steam cracker product stream by passing said stream through a carbon dioxide removal unit where it can be contacted with an aqueous solution of a base such as sodium hydroxide (caustic soda wash). Hydrogen and methane can be separated from other components by cryogenic distillation. Alternatively, hydrogen and methane can be separated from any C3+ hydrocarbons in the product stream along with C2 hydrocarbons containing ethylene, any unreacted ethane and any acetylene. The C2 hydrocarbons must then be separated from the resulting stream containing hydrogen, methane and C2 hydrocarbons. Acetylene can be removed by hydrogenating it to ethylene. Finally, ethane must be separated from ethylene, which can also be done by distillation. The need to remove all of these components from the product stream of the steam cracker containing ethylene is very laborious and leads to relatively high costs for the production of ethylene. For example, a process is known for separating ethane from ethylene by means of cryogenic distillation in so-called C2 strippers. For such cryogenic distillation, relatively high pressure and relatively low (cryogenic) temperature are used to achieve the effect of separating ethane and ethylene.

The next section of the ethane steam cracker circuit, which is the next section of the processing and may contain several units for performing the above functions of removing carbon dioxide, separating components (for example, by distillation) and hydrogenating acetylene, has a certain capacity, which is determined by the unit with the smallest capacity . In general, a situation may arise in which the capacity of the steam cracker located upstream of the next section in the steam cracker circuit does not correspond to the higher productivity of the next section. In this case, the power of the next section is not fully loaded, which leads to a technically unfavorable, inefficient and less economical process for producing ethylene from ethane.

The above situation, in which the capacity of the steam cracker (comprising one or more furnaces) located upstream of the next section in the ethane steam cracker circuit does not match the higher capacity of the next section, can usually occur when there is a bottleneck in the existing steam cracker circuit or if necessary expansion of the total capacity of the steam cracking scheme. This may include a situation in which the life of the steam cracker is nearing or nearing the end of its service life. In addition, this may include a situation in which unrealized potential in the final separation section of an existing steam cracking circuit must be exploited at the expense of design margin (design reserve of distillation columns or installation of higher capacity internals) and/or at the capacity of the steam cracking furnace(s). below calculated. The latter case can also be the result of the reconstruction of the existing liquid feed steam cracking circuit into a gas (ethane) steam cracking circuit. It may also refer to situations in which 1 or more of a plurality of steam crackers need to be decommissioned (for example, for maintenance or for any other reason).

It is an object of the present invention to provide a process for producing ethylene from ethane, which may have a technical advantage, which may be an efficient and inexpensive process, and which involves the steam cracking of ethane into ethylene and hydrogen in a steam cracker that is part of a steam cracker scheme, more specifically, in such a situation, in which the capacity of the steam cracker located before the next section in the steam cracker circuit does not correspond to the higher productivity of the next section. Such a technically advantageous method would preferably result in a reduction in energy consumption and/or a reduction in capital costs.

The essence of the invention

Surprisingly, it has been found that the above object can be solved by feeding the oxidative dehydrogenation (ODH) circuit effluent to a steam cracking circuit, wherein the ethane in the ODH circuit is oxidatively dehydrogenated to ethylene and water, and the effluent from the ODH circuit is and fed to the steam cracking circuit contains unreacted ethane and ethylene.

Accordingly, this invention relates to a process for producing ethylene, comprising processing a stream containing ethane or naphtha, under steam cracking conditions in a steam cracker, which is part of a steam cracking circuit, obtaining a stream containing unreacted ethane, ethylene and hydrogen;

feeding a stream containing unreacted ethane, ethylene and hydrogen to a separation plant that is part of the steam cracking scheme, and separating said stream in said separation plant into a stream containing hydrogen and a stream containing unreacted ethane and ethylene;

feeding a stream containing unreacted ethane and ethylene to a C2 separation unit that is part of a steam cracking scheme, and separating said stream in said C2 separation unit into a stream containing ethylene and a stream containing unreacted ethane;

optional recycling of unreacted ethane from the unreacted ethane containing stream from the C2 separation unit to the steam cracker;

processing the ethane-containing stream under oxidative dehydrogenation (ODH) conditions in an ODH unit that is part of the ODH scheme to produce a stream containing unreacted ethane, ethylene and water;

feeding a stream containing unreacted ethane, ethylene and water to a water condensing unit that is part of the ODH scheme, and removing water from said stream by condensing water in the water condensing unit to obtain a stream containing unreacted ethane and ethylene;

feeding the effluent from the ODH circuit, which contains unreacted ethane and ethylene, to the steam cracking circuit;

optional recycle of unreacted ethane from the unreacted ethane containing stream from the C2 separation unit to the ODH unit.

In addition, this invention relates to a chemical complex that contains a steam cracking circuit and an oxidative dehydrogenation (ODH) circuit, in which the steam cracking circuit contains a steam cracker, a carbon dioxide removal unit, an optional dryer, a 1st separation plant, a 2- a second separation unit, an optional acetylene hydrogenation unit, and a C ₂ separation unit, each unit comprising one or more feed lines and one or more exhaust lines;

the ODH scheme comprises an ODH plant, a water condensing unit, an optional carbon dioxide removal unit, and an optional dryer unit, each unit comprising one or more supply lines and one or more exhaust lines;

the ODH circuit is integrated with the steam cracker circuit upstream of the optional acetylene hydrogenation unit and upstream of the C2 separation unit and no ODH plant feed line is integrated with the plant feed or outlet line in the steam cracker circuit, except that the steam cracker feed line and the supply line of the ODH plant may be integrated, and/or that the optional recycle line of the stream exiting the separation unit C2 and the supply line of the ODH plant may be integrated.

Brief description of graphic materials

In FIG. 1 shows one embodiment of the present invention in which the oxidative dehydrogenation (ODH) water condenser effluent containing unreacted ethane and ethylene is fed to a steam cracker.

In FIG. 2 shows one embodiment of the present invention in which the effluent from the carbon dioxide removal unit in the ODH circuit, containing unreacted ethane and ethylene, is fed to the steam cracker circuit.

In FIG. 3 shows one embodiment of the present invention in which the dryer effluent from the ODH circuit, containing unreacted ethane and ethylene, is fed to the steam cracker circuit.

Detailed description of the invention

The integrated process of this invention uses both a steam cracking scheme and an oxidative dehydrogenation (ODH) scheme.

The above steam cracking scheme contains:

(a) a steam cracker in which the ethane-containing stream is subjected to conditions

- 2 042704 steam cracking to obtain a stream containing unreacted ethane, ethylene and hydrogen;

(b) a separating unit in which a stream containing unreacted ethane, ethylene and hydrogen is separated into a stream containing hydrogen and a stream containing unreacted ethane and ethylene;

(c) a C2 separation unit in which a stream containing unreacted ethane and ethylene is separated into a stream containing ethylene and a stream containing unreacted ethane.

Furthermore, in accordance with the present invention, the steam cracking circuit may comprise a carbon dioxide removal unit, a dryer unit, one or more separation units other than the aforementioned C2 separation unit, an acetylene hydrogenation unit, and/or one or more compressors.

The above oxidative dehydrogenation (ODH) scheme contains:

(i) an ODH plant in which the ethane-containing stream is subjected to ODH conditions to produce a stream containing unreacted ethane, ethylene and water;

(ii) a water condensing unit in which water is removed from the stream containing unreacted ethane, ethylene and water by condensing to obtain a stream containing unreacted ethane and ethylene.

In addition, in accordance with the present invention, the ODH scheme may include a carbon dioxide removal unit and a dryer unit.

In accordance with the present invention, the integration between the aforementioned steam cracking circuit and the ODH circuit is carried out by feeding the effluent from the ODH circuit containing unreacted ethane and ethylene into the steam cracking circuit. In particular, in accordance with the present invention, the effluent from the ODH circuit, containing unreacted ethane and ethylene, is fed to the steam cracker circuit in a position after the steam cracker.

WO 2014134703 describes the incorporation of an ethane ODH process into a product recovery process that is carried out in the next section of an ethane steam cracker circuit, whereby the ODH unit becomes part of the steam cracker circuit and the ethane containing feed stream for the ODH plant comes from the steam cracker circuit only.

In FIG. 4 of WO 2014134703, a C2 stripper for separating ethylene from ethane, which is part of a steam cracking scheme, is connected to an ODH unit at the bottom of the C2 stripper. That is, in the method depicted in said FIG. 4, ethane from the bottom of the C2 stripper is fed to an ODH unit downstream of the C2 stripper. In the method shown in FIG. 6 of WO 2014134703, ethane and ethylene are fed from the middle part of the C2 stripper to an ODH unit downstream of the C2 stripper. In the method shown in FIG. 8 of WO 2014134703, ethane and ethylene from the hydrogenation units that are part of the steam cracking scheme are fed to the ODH unit, which is located downstream of said hydrogenation units. In all of these methods depicted in FIG. 4, 6 and 8 of WO 014134703, none of the effluents from the ODH unit are fed into the steam cracker at any position.

In addition, in FIG. 7 of WO 2014134703, ethane and ethylene from the steam cracker are fed to the ODH unit, the effluent from which is sent to a C2 stripper to separate ethylene from ethane, and said stripper is part of the steam cracker circuit. That is, in the method shown in said FIG. 7, ethane and ethylene from the steam cracker are fed to the ODH unit upstream of the C2 stripper. In the method shown in FIG. 7 of WO 2014134703, the ODH unit is part of a steam cracking scheme. There is no separate ODH scheme. Since the inlet to the ODH unit originates from the steam cracker and the effluent from the ODH unit is fed to the C2 stripper, both the steam cracker and the C2 stripper are part of the steam cracker circuit.

In all of the aforementioned methods depicted in FIG. 4, 6, 7 and 8 of WO 2014134703, an ODH plant incorporated into a steam cracker circuit cannot be a means to ensure that the production capacity of the next section in the steam cracker circuit can be fully utilized, in a situation in which the capacity of the steam cracker located upstream specified next section does not correspond to the higher performance of the next section. Because the streams that enter the ODH installations in these FIGS. 4, 6, 7 and 8 come directly or indirectly from the steam cracker effluent. As stated in WO 2014134703 (see page 46), the invention described in WO 2014134703 is based on the conversion of (not yet reacted) ethane from a cracker product stream to ethylene in an ODH co-plant, in order to reduce the ethane load on the system separation facilities. This differs from the present invention, in which more effluent, i.e., both the effluent from the steam cracker and the effluent from the ODH unit, can be fed to the next section of the steam cracker circuit, compared to other cases in which the amount of effluent which can be fed to said downstream section of the steam cracker circuit can only be determined by the effluent coming from the steam cracker. Examples of these

- 3 042704 other cases are (i) cases in which no ODH setting is used at all; or (ii) the cases described above, illustrated in the ways depicted in FIG. 4, 6, 7 and 8 in WO 2014134703, in which the ethane ODH process is integrated into the product recovery process carried out in the next section of the ethane steam cracker circuit, where the ODH unit becomes part of the steam cracker circuit and the ethane-containing feed stream for the ODH plant comes only from the scheme of steam cracking.

Thus, the present invention provides a process for producing ethylene from ethane, including steam cracking of ethane to ethylene and hydrogen, and said process may be technically more advantageous, more efficient, and more economical than the other cases described above. Such a technically advantageous method may advantageously provide a reduction in energy consumption and/or a reduction in capital costs.

In particular, by integrating the ODH circuit with the steam cracking circuit, by feeding the effluent from the ODH circuit containing unreacted ethane and ethylene into the steam cracking circuit, in particular into the downstream section of the steam cracking circuit, by feeding said effluent into a steam cracker circuit at a position after a steam cracker, the present invention is useful for overcoming a bottleneck in an existing steam cracker circuit or for expanding the overall capacity of a steam cracker circuit. Thus, the relatively high capacity of the next section in the ethane steam cracker circuit can be advantageously fully utilized compared to the capacity of the steam cracker (comprising one or more furnaces) located upstream of said next section. This may include a situation in which the life of the steam cracker is nearing or nearing the end of its service life. In addition, this would include a situation in which unrealized potential in the final separation section of an existing steam cracking circuit needs to be exploited at a design margin (design reserve of distillation columns or installation of higher capacity internals) and/or at a capacity of the steam cracking furnace(s) below calculated. The latter case can also be the result of the reconstruction of the existing liquid feed steam cracking circuit into a gas (ethane) steam cracking circuit. It may also refer to situations in which 1 or more of a plurality of steam crackers need to be decommissioned (for example, for maintenance or for any other reason). The above examples demonstrate that the implementation of this invention can be advantageously applied in many practical situations to achieve a technically advantageous, efficient and economical integrated process for the production of ethylene from ethane, including both steam cracking of ethane to ethylene and hydrogen, and oxidative dehydrogenation of ethane to ethylene and water.

In addition to allowing full use of the relatively high power of the next section in the ethane steam cracking circuit as described above, the present invention also has the following additional advantages. The ethane ODH scheme, comprising an ODH plant (eg ODH reactor) and a water condensing plant, has a small footprint (less footprint required), low capital intensity, low energy consumption and hence low overall CO ₂ emissions. The ethane ODH process requires less energy for the compressors and distillation columns because the ODH off-gas has a higher molecular weight (ODH effluent is substantially free of light components such as hydrogen and methane compared to, for example, ethane steam cracking) , the ODH process can be carried out at high pressure (eg 2-10 bar) and finally it is an exothermic chemical process which produces high pressure clean steam which can also advantageously be used in the chemical complex of this invention. With respect to the latter, the steam produced in the ODH process can advantageously be used in the steam cracking circuit of the proposed chemical complex. Conversely, steam produced from the steam cracking process can advantageously be used in the ODH scheme of the proposed chemical complex. In addition, the ODH process typically produces a much narrower product range (i.e. no or fewer by-products such as methane and C3+ hydrocarbons from ethane steam cracking), but the ODH effluents are still chemically compatible. with ethane steam cracker effluents, greatly simplifying layout and separation requirements and reducing capital and energy costs.

These and other advantages of the present invention will also become apparent from the following detailed description.

In the context of this description, the following terms have the following meanings.

C3+ hydrocarbons include hydrocarbons containing 3 or more carbon atoms. C3+ hydrocarbons may include propane and/or propylene.

C2+ hydrocarbons include hydrocarbons containing 2 or more carbon atoms. The C2+ hydrocarbons may include ethane, ethylene, acetylene, propane and/or propylene.

C2 hydrocarbons include hydrocarbons containing 2 carbon atoms. The C2 hydrocarbons may include ethane, ethylene and/or acetylene.

- 4 042704

With respect to the process of the present invention, a steam cracker means a plant in which ethane is converted to ethylene and hydrogen under steam cracking conditions. With respect to the complex of this invention, a steam cracker means a plant that is capable of converting ethane under steam cracking conditions into ethylene and hydrogen. The steam cracker may include a furnace.

With respect to the process of the present invention, an oxidative dehydrogenation plant means a plant in which ethane is converted under oxidative dehydrogenation (ODH) conditions into ethylene and water. With respect to the complex of this invention, an oxidative dehydrogenation plant means a plant that is suitable for converting ethane under ODH conditions to ethylene and water. The ODH unit may comprise a reactor, which may be a catalytic reactor, which is a reactor containing a catalyst.

With respect to the process of the present invention, a carbon dioxide removal plant means a plant in which carbon dioxide is removed from a stream containing ethylene, hydrogen and carbon dioxide. With respect to the complex of this invention, a carbon dioxide removal plant means a plant that is suitable for removing carbon dioxide from a stream containing ethylene, hydrogen and carbon dioxide. The carbon dioxide removal agent fed into the carbon dioxide removal unit may be an aqueous solution of a base such as sodium hydroxide or an amine.

With respect to the process of the present invention, a dryer means a plant in which water is removed from a stream containing ethylene, hydrogen and water. With respect to the complex of this invention, a dryer means a plant that is suitable for removing water from a stream containing ethylene, hydrogen and water.

With respect to the process according to the invention, an acetylene hydrogenation plant means a plant in which acetylene is converted into ethylene under hydrogenation conditions. With respect to the complex of the present invention, an acetylene hydrogenation plant means a plant which is suitable for converting acetylene under hydrogenation conditions to ethylene. The acetylene hydrogenation unit may comprise a reactor, which may be a catalytic reactor, which is a reactor containing a catalyst.

With respect to the process according to the invention, a C2 separation plant means a plant in which ethylene is separated from ethane. With respect to the complex of this invention, a C2 separation plant means a plant which is suitable for separating ethylene from ethane. Ethylene can be separated from ethane by any means, such as distillation, absorption or adsorption.

In addition, while the process and chemistry as well as the circuits of this invention and the stream or streams used in said process are described in terms of comprising, comprising, or comprising one or more of the various steps or units described, or components, they may also consist essentially of or consist of said one or more of the various stages or installations or components described.

In the context of this invention, if the stream contains two or more components, these components should be selected in a total amount not exceeding 100 vol.% or 100 wt.%.

The proposed method is a method for producing ethylene from ethane, including processing a stream containing ethane, under steam cracking conditions in a steam cracker, which is part of a steam cracking scheme, to obtain a stream containing unreacted ethane, ethylene and hydrogen;

feeding a stream containing unreacted ethane, ethylene and hydrogen to a separation plant that is part of the steam cracking scheme, and separating said stream in said separation plant into a stream containing hydrogen and a stream containing unreacted ethane and ethylene;

feeding a stream containing unreacted ethane and ethylene to a C2 separation unit that is part of a steam cracking scheme, and separating said stream in said C2 separation unit into a stream containing ethylene and a stream containing unreacted ethane;

optional recycling of unreacted ethane from the unreacted ethane containing stream from the C2 separation unit to the steam cracker;

processing the ethane-containing stream under oxidative dehydrogenation (ODH) conditions in an ODH unit that is part of the ODH scheme to produce a stream containing unreacted ethane, ethylene and water;

feeding a stream containing unreacted ethane, ethylene and water to a water condensing unit that is part of the ODH scheme, and removing water from said stream by condensing water in the water condensing unit to obtain a stream containing unreacted ethane and ethylene;

supplying an effluent coming from the ODH circuit that contains unreacted

- 5 042704 ethane and ethylene, to the steam cracking scheme;

optional recycle of unreacted ethane from the unreacted ethane containing stream from the C2 separation unit to the ODH unit.

As described above, in accordance with the present invention, the integration between the steam cracker circuit and the ODH circuit is carried out by feeding the effluent from the ODH circuit containing unreacted ethane and ethylene into the steam cracker circuit, in particular at the position after the steam cracker. In addition, in particular, unreacted ethane from the effluent from the steam cracker circuit is not fed to the ODH unit in the ODH circuit, except for the optional recycle of unreacted ethane from the effluent from the C2 separation unit in the steam cracker circuit to the unit ODH in the ODH scheme. Moreover, in particular, the ODH unit is supplied with ethane that is obtained from one or more sources selected from the group consisting of: a) a fresh ethane source that is used to feed ethane to the steam cracker; b) another source of fresh ethane other than the specified first source referred to in paragraph a); and c) unreacted ethane from the effluent from the C2 separation unit. In the context of this description, fresh ethane is understood to mean ethane that does not contain unreacted ethane. In the context of this description, unreacted ethane is understood to mean ethane that has been subjected to either steam cracking conditions or oxidative dehydrogenation conditions in the process of this invention, but has not reacted. With respect to the sources of fresh ethane mentioned in a) and b) above, the fresh ethane that is subjected to the steam cracking and/or oxidative dehydrogenation conditions in the process of this invention may be obtained from a plant producing a stream containing ethane, either as a main stream or as a side stream, such as a gas production plant, a gas processing plant, a plant for the recovery and fractionation of a wide fraction of light hydrocarbons (NGLs), a plant for the production of liquefied natural gas (LNG), etc., and these plants may also be referred to generically as hydrocarbon transport and storage plants. Thus, the proposed method can be integrated with any of these hydrocarbon transportation and storage plants. However, according to the invention, the origin of the fresh ethane is not critical.

In general, in accordance with this invention, the raw material for the ODH plant may include: 1) unreacted ethane and no fresh ethane; or 2) unreacted ethane and fresh ethane; or 3) fresh ethane and no unreacted ethane. In the same way, in general, in accordance with this invention, the feed for the steam cracker may include: 1) unreacted ethane and no fresh ethane; or 2) unreacted ethane and fresh ethane; or 3) fresh ethane and no unreacted ethane. In particular, fresh ethane can be fed into the ODH unit. In addition, in particular, fresh ethane can be fed into the steam cracker. Also, in particular, fresh ethane can be fed to both the ODH unit and the steam cracker. As described above, feeding fresh ethane means feeding ethane that has not been subjected to either steam cracking conditions or oxidative dehydrogenation (ODH) conditions. The fresh ethane fed to the ODH unit and the fresh ethane fed to the steam cracker may come from the same source or from different sources.

In accordance with the proposed method, the effluent stream from the ODH circuit containing unreacted ethane and ethylene, which is fed to the steam cracker circuit, may be a stream containing unconverted ethane and ethylene from the water condenser in the ODH circuit. Preferably, unreacted ethane and ethylene from the stream containing unreacted ethane and ethylene coming from the water condensation unit in the ODH scheme is fed to the C2 separation unit in the steam cracking scheme.

In accordance with the proposed method, the stream coming from the steam cracker in the steam cracker circuit may contain unreacted ethane, ethylene, hydrogen, methane, carbon monoxide, carbon dioxide and C3+ hydrocarbons; and the stream coming from the ODH plant in the ODH scheme may contain unreacted ethane, ethylene, water, carbon monoxide and carbon dioxide. In such a case, the method for producing ethylene according to this invention may include the following steps:

treating the ethane-containing stream under steam cracking conditions in a steam cracker that is part of the steam cracking circuit to produce a stream containing unreacted ethane, ethylene, hydrogen, methane, carbon monoxide, carbon dioxide, and C3+ hydrocarbons;

feeding a stream containing unreacted ethane, ethylene, hydrogen, methane, carbon monoxide, carbon dioxide, and C3+ hydrocarbons to a carbon dioxide removal unit that is part of the steam cracking circuit, and removing carbon dioxide from said stream in said carbon dioxide removal unit to obtain a stream containing unreacted ethane, ethylene, hydrogen, methane, carbon monoxide and C3+ hydrocarbons;

feeding a stream containing unreacted ethane, ethylene, hydrogen, methane, carbon monoxide and C3+ hydrocarbons to a separation unit that is part of the steam cracking scheme,

- 6 042704 and separation of the specified stream in the specified separation unit into a stream containing hydrogen, methane and carbon monoxide, and a stream containing C3 + hydrocarbons;

feeding unreacted ethane and ethylene from a stream containing unreacted ethane, ethylene, hydrogen, methane, carbon monoxide and C3+ hydrocarbons to a C2 separation unit, which is part of a steam cracking scheme, and separating said stream in said C2 separation unit into a stream containing ethylene, and a stream containing unreacted ethane;

optional recycling of unreacted ethane from the unreacted ethane containing stream from the C2 separation unit to the steam cracker;

processing the ethane-containing stream under oxidative dehydrogenation (ODH) conditions in an ODH unit that is part of the ODH scheme to produce a stream containing unreacted ethane, ethylene, water, carbon monoxide, and carbon dioxide;

feeding a stream containing unreacted ethane, ethylene, water, carbon monoxide and carbon dioxide to a water condensing unit that is part of the ODH scheme, and removing water from said stream by condensing water in the water condensing unit to obtain a stream containing unreacted ethane, ethylene , carbon monoxide and carbon dioxide;

feeding the effluent from the ODH circuit, which contains unreacted ethane and ethylene, to the steam cracking circuit;

optional recycle of unreacted ethane from the unreacted ethane containing stream from the C2 separation unit to the ODH unit.

In addition, the stream coming from the ODH plant in the ODH scheme may also contain unreacted oxygen (used as an oxidizing agent in the ODH process). Preferably, said unreacted oxygen is removed before the ODH circuit effluent containing unconverted ethane and ethylene is fed to the steam cracker circuit, for safety reasons and taking into account the presence of hydrogen in the steam cracker effluents.

In the carbon dioxide removal step of the process described above, a stream containing unreacted ethane, ethylene, hydrogen, methane, carbon monoxide, carbon dioxide and C3+ hydrocarbons is fed to a carbon dioxide removal unit in a steam cracking circuit. The latter stream may be a stream coming from a steam cracker. Optionally, if the stream containing unreacted ethane, ethylene, hydrogen, methane, carbon monoxide, and C3+ hydrocarbons from the carbon dioxide removal step contains water, then said stream is fed to a dryer, which is part of the steam cracking circuit, to remove water.

In addition, in the process described above, a stream containing unreacted ethane, ethylene, hydrogen, methane, carbon monoxide and C3+ hydrocarbons is fed to the separation unit of the steam cracking circuit. The latter stream may be a stream coming from the aforementioned carbon dioxide removal plant or an optional dryer. In the last separation plant, the last stream is separated into a stream containing hydrogen, methane and carbon monoxide and a stream containing C3+ hydrocarbons. In the 1st embodiment of the invention, said stream containing unreacted ethane, ethylene, hydrogen, methane, carbon monoxide and C3+ hydrocarbons is separated into a stream containing hydrogen, methane and carbon monoxide, and a stream containing C2+ hydrocarbons, and said C2+ hydrocarbons contain unreacted ethane, ethylene and C3+ hydrocarbons. In the 2nd embodiment of the invention, the specified stream containing unreacted ethane, ethylene, hydrogen, methane, carbon monoxide and C3+ hydrocarbons is divided into a stream containing hydrogen, methane, carbon monoxide and C2 hydrocarbons, with C2 hydrocarbons containing unreacted ethane and ethylene, and a stream containing C3+ hydrocarbons. In said 1st embodiment, the separated stream containing C2+ hydrocarbons can be fed to a further separation plant, where said stream is separated into a stream containing C2 hydrocarbons and a stream containing C3+ hydrocarbons. In said 2nd embodiment, the separated stream containing hydrogen, methane, carbon monoxide and C2 hydrocarbons can be fed to the next separation plant, where said stream is separated into a stream containing hydrogen, methane and carbon monoxide and a stream containing C2 hydrocarbons. In both of these embodiments, the separated stream containing C2 hydrocarbons coming from said next separation unit may be fed to the above C2 separation unit in a steam cracking scheme, where the latter stream is separated into a stream containing ethylene and a stream containing unreacted ethane.

In addition, in the above process, the stream containing unreacted ethane, ethylene, carbon monoxide and carbon dioxide, which comes from the water condensation unit in the ODH scheme, can be fed to the carbon dioxide removal unit, which is part of the ODH scheme, where carbon dioxide is removed from the specified stream to obtain a stream containing unreacted ethane, ethylene and carbon monoxide. Optionally, if the stream containing unreacted ethane, ethylene and carbon monoxide from the carbon dioxide removal step contains water, then said stream may be fed to a dryer, which is part of the ODH scheme, to remove water.

- 7 042704

In addition, in the above process, the effluent from the OD circuit containing unreacted ethane and ethylene is fed to the steam cracker circuit. In particular, said outflow coming from the ODH scheme is an outflow coming directly or indirectly from the ODH installation.

In the above process, the above effluent from the ODH circuit containing unreacted ethane and ethylene, which is fed to the steam cracking circuit, may be a stream containing unconverted ethane, ethylene, carbon monoxide and carbon dioxide coming from the water condenser in the ODH circuit. . Preferably, the last stream containing unreacted ethane, ethylene, carbon monoxide and carbon dioxide coming from the water condensation unit in the ODH scheme is fed to the carbon dioxide removal unit in the steam cracking scheme. This is shown in FIG. 1 (line 35).

Further, in the process described above, the aforementioned effluent from the ODH circuit containing unreacted ethane and ethylene that is fed to the steam cracking circuit may be a stream containing unreacted ethane, ethylene and carbon monoxide from an optional carbon dioxide removal unit in ODH scheme. Preferably, the last stream containing unreacted ethane, ethylene and carbon monoxide coming from the optional carbon dioxide removal unit in the ODH scheme is fed to the separation unit of the steam cracking scheme, where the stream containing unreacted ethane, ethylene, hydrogen, methane, carbon monoxide and C3+ hydrocarbons , is separated into a stream containing hydrogen, methane and carbon monoxide, and a potto containing C3+ hydrocarbons. If the streams from the carbon dioxide removal steps contain water as described above, then the stream from the carbon dioxide removal unit in the ODH scheme may be fed to the aforementioned dryer in the steam cracking scheme. This is shown in FIG. 2 (line 40). In addition, if the streams from the carbon dioxide removal steps contain water and the ODH scheme contains a dryer as described above, then the stream coming from the dryer in the ODH scheme containing unreacted ethane, ethylene and carbon monoxide , can be fed to said separation unit in a steam cracking scheme in which a stream containing unreacted ethane, ethylene, hydrogen, methane, carbon monoxide and C3+ hydrocarbons is separated into a stream containing hydrogen, methane and carbon monoxide and a stream containing C2+ hydrocarbons (the above-described 1st embodiment of the invention). This is shown in FIG. 3 (line 45). In addition, if the streams from the carbon dioxide removal steps contain water and the ODH scheme contains a dryer as described above, then the stream coming from the dryer in the ODH scheme containing unreacted ethane, ethylene and carbon monoxide , can be fed to said separation unit in a steam cracking scheme in which a stream containing hydrogen, methane, carbon monoxide and C2 hydrocarbons is separated into a stream containing hydrogen, methane and carbon monoxide and a stream containing C2 hydrocarbons (the above-described 2nd embodiment of the invention). This is also shown in FIG. 3 (line 46).

In the proposed method, the stream coming from the steam cracker of the steam cracker circuit may additionally contain acetylene; and the stream coming from the ODH unit of the ODH scheme may additionally contain acetylene. In such a case, the ethylene production process of this invention may include an acetylene hydrogenation step in which, in an acetylene hydrogenation unit, a stream containing unreacted ethane, ethylene and acetylene is subjected to hydrogenation conditions to convert acetylene to ethylene.

Preferably, the acetylene hydrogenation unit is part of a steam cracking scheme. In the latter case, a stream containing unreacted ethane, ethylene and acetylene may be fed to an acetylene hydrogenation unit in a steam cracking circuit to produce a stream containing unreacted ethane and ethylene, and said latter stream may be fed to the aforementioned C2 separation unit. In such a case, the hydrogen containing stream may be fed to an acetylene hydrogenation unit in a steam cracking circuit. Hydrogen is a hydrogenating agent that can hydrogenate acetylene to ethylene and can be obtained from a steam cracking scheme.

More specifically, in the proposed method, in the presence of acetylene as described above, in the aforementioned 1st embodiment of the invention, the stream containing unreacted ethane, ethylene, acetylene, hydrogen, methane, carbon monoxide and C3+ hydrocarbons is separated into a stream containing hydrogen, methane and carbon monoxide; and a stream containing C2+ hydrocarbons, wherein the C2+ hydrocarbons include unreacted ethane, ethylene, acetylene, and C3+ hydrocarbons. In addition, in the above 2nd embodiment of the invention, the stream containing unreacted ethane, ethylene, acetylene, hydrogen, methane, carbon monoxide and C3+ hydrocarbons is separated into a stream containing hydrogen, methane, carbon monoxide and C2 hydrocarbons, and C2 hydrocarbons contain unreacted ethane, ethylene and acetylene, and a stream containing C3+ hydrocarbons. In said 1st embodiment, the separated stream containing C2+ hydrocarbons can be fed to a further separation plant, where said stream is separated into a stream containing C2 hydrocarbons and a stream containing C3+ hydrocarbons. In said 2nd embodiment, the separated stream containing hydrogen, methane, carbon monoxide and C2 hydrocarbons can be fed to the next separation plant, where said stream is separated into a stream containing hydrogen, methane and carbon monoxide, and a stream containing hydrogen, methane and carbon monoxide, and a stream containing hydrocarbons C2. In both of these embodiments, the separated stream containing C2 hydrocarbons coming from said next separation unit can be fed to the acetylene hydrogenation unit, which is part of the steam cracking circuit, where acetylene is converted to ethylene to obtain a stream containing unreacted ethane and ethylene, and said last stream may then be fed to the aforementioned C2 separation unit in a steam cracking circuit, where said last stream is separated into a stream containing ethylene and a stream containing unreacted ethane.

In the process of this invention, a stream containing ethane is subjected to steam cracking conditions in a steam cracker that is part of a steam cracker circuit to produce a stream containing unreacted ethane, ethylene and hydrogen. Suitable steam cracking conditions for this steam cracking step are described below.

In particular, in the aforementioned steam cracking step, no oxygen-containing stream is fed into the steam cracker since it is not necessary to use oxygen as an oxidizing agent. However, carbon dioxide can still form as an impurity in the presence of oxygen (due to small amounts of air being introduced into the steam cracker) and/or in hydrocarbon steam reforming reactions. In addition, carbon monoxide and carbon dioxide may enter the steam cracking process as impurities in the feedstock.

In addition, in particular, no catalyst is used in the above-mentioned steam cracking step. Preferably, said steam cracking step is carried out at an elevated temperature, more preferably in the range of 650 to 1000°C, most preferably 750 to 950°C. Methods for the steam cracking of hydrocarbons are well known. For example, see Kniel et al., Ethylene, Keystone to the petrochemical industry, Marcel Dekker, Inc, New York, 1980, in particular chapters 6 and 7.

In the process of this invention, an ethane-containing stream is subjected to oxidative dehydrogenation (ODH) conditions in an ODH unit, which is part of an ODH scheme, to produce a stream containing unreacted ethane, ethylene, and water. Suitable ODH conditions for this ODH step are described below.

In the above ODH step, processing the ethane-containing stream under ODH conditions may include contacting the ethane-containing stream with oxygen (O ₂ ). Said oxygen is the oxidizing agent in this ODH reaction. In the ODH stage, oxygen (O ₂ ) and an ethane-containing stream may be fed to the ODH unit. The ODH unit may comprise a reactor which may contain an ODH catalyst, in particular a mixed metal oxide catalyst containing molybdenum, vanadium, niobium and optionally tellurium. Oxygen and ethane are then brought into contact with said catalysts in an ODH reactor, resulting in the oxidative dehydrogenation of ethane.

In the ODH step of the process of this invention, oxygen and ethane can be fed into the reactor together or separately. That is, one or more feed streams, in particular gaseous streams containing one or more of these 2 components, can be fed into the reactor. For example, a single feed stream containing oxygen and ethane can be fed to the reactor. Alternatively, two or more feed streams, in particular gaseous streams, may be fed into the reactor, and said feed streams may form a combined stream within the reactor. For example, one feed stream containing oxygen and another feed stream containing ethane can be separately fed to the reactor.

In addition, in the ODH step of the process according to the invention, in particular when oxygen and ethane are brought into contact with an ODH catalyst, the temperature is between 300 and 500°C. More preferably, said temperature is 310 to 450°C, more preferably 320 to 420°C, most preferably 330 to 420°C.

Moreover, in the aforementioned ODH step, in particular when bringing oxygen and ethane into contact with an ODH catalyst, a typical pressure is 0.1-30 or 0.1-20 bar abs. (i.e. bar absolute pressure). In addition, said pressure is preferably 0.1 to 15 bar abs., more preferably 1 to 8 bar abs., most preferably 3 to 8 bar abs.

The product of the above ODH step contains the dehydrated analogue of ethane, i.e. ethylene. In this step, ethylene is initially produced. However, in the same said step, ethylene can be further oxidized under the same conditions to the corresponding carboxylic acid, ie to acetic acid.

In addition to oxygen and ethane, an inert gas can also be fed into the ODH reactor. Said inert gas may be selected from the group consisting of noble gases and nitrogen (N2). Preferably the inert gas is nitrogen or argon, more preferably nitrogen. The specified oxygen is an oxidizing agent that provides oxidative dehydrogenation of ethane. The specified oxygen can be obtained from any source, such as, for example, air. Suitable molar ratios of oxygen to ethane range from 0.01 to 1, more specifically from 0.05 to 0.5. The ratio of oxygen to ethane given is the ratio before bringing oxygen and ethane into contact

- 9 042704 with catalyst. In other words, the specified ratio of oxygen to ethane is the ratio of oxygen as a raw material to ethane as a raw material. Obviously, after bringing into contact with the catalyst, at least part of the oxygen and ethane is consumed.

Preferably, in the ODH step of the process of this invention, the ODH catalyst is a heterogeneous catalyst. In addition, the ODH catalyst is preferably a mixed metal oxide catalyst containing molybdenum, vanadium, niobium, and optionally tellurium as metals, and said catalyst may have the following formula:

M _O1 V _a Te _b Nb _c 0 _n where a, b, c and n are the ratio of the molar amount of the element in question to the molar amount of molybdenum (Mo);

a (for V) is 0.01 to 1, preferably 0.05 to 0.60, more preferably 0.10 to 0.40, more preferably 0.20 to 0.35, most preferably 0, 25 to 0.30;

b (for Te) is 0 or >0 to 1, preferably 0.01 to 0.40, more preferably 0.05 to 0.30, more preferably 0.05 to 0.20, most preferably 0.05 to 0.20 0.09 to 0.15;

c (for Nb) is >0 to 1, preferably 0.01 to 0.40, more preferably 0.05 to 0.30, more preferably 0.10 to 0.25, most preferably 0.14 up to 0.20 and n (for O) is a value that is determined by the valency and the number of elements other than oxygen.

The amount of catalyst in the above ODH step is not critical. Preferably, a catalytically effective amount of catalyst is used, ie an amount sufficient to promote the oxidative dehydrogenation of ethane.

The ODH reactor that can be used in the above ODH step may be any reactor, including fixed bed reactors and fluidized bed reactors. In particular, the reactor is a fixed bed reactor.

Examples of oxidative dehydrogenation processes, including catalysts and process conditions, are described, for example, in the aforementioned US Pat.

During the ODH reaction of ethane, which takes place in the ODH step of the proposed process, water is formed. In the process of the present invention, the stream containing unreacted ethane, ethylene and water, in particular the stream containing unreacted ethane, ethylene and water obtained from said ODH stage, is fed to a water condensing unit which is part of the ODH scheme and the water is removed from said stream by condensing in a water condensing unit to obtain a stream containing unreacted ethane and ethylene. In said water condensation step, water can easily be condensed in the stream containing unreacted ethane, ethylene, and water by cooling the latter stream to a lower temperature, such as room temperature, after which the condensed water can be removed from the stream containing unreacted ethane, ethylene, and water.

According to the present invention, carbon dioxide can be removed from carbon dioxide containing streams by any of the commonly known methods. As mentioned above, a suitable carbon dioxide removal agent that can be fed into the carbon dioxide removal unit may be an aqueous solution of a base such as sodium hydroxide or an amine. After such removal of carbon dioxide, said stream must be dried in a dryer to remove residual water from the stream. Contacting an aqueous amine solution with a stream containing carbon dioxide is preferred if the carbon dioxide content is relatively high, such as in the case of an ethane ODH plant effluent. Contacting an aqueous sodium hydroxide solution with a stream containing carbon dioxide is preferred if the carbon dioxide content is relatively low, for example 1) in the case of an ethane steam cracker effluent or 2) in the case of an ethane ODH plant effluent, which has been treated with an aqueous amine solution and still contains a small amount of residual carbon dioxide. In accordance with the present invention, a carbon dioxide removal plant as part of a steam cracking scheme may comprise a block where carbon dioxide is removed with an aqueous amine solution, and a further block where carbon dioxide is removed with an aqueous sodium hydroxide solution. In the latter case, it may be preferable that the carbon dioxide-containing effluent from the water condenser in the ODH scheme is fed to the first unit, where the carbon dioxide is removed with an aqueous amine solution. In addition, a carbon dioxide removal unit as part of a steam cracking scheme may only comprise a unit in which carbon dioxide is removed with an aqueous sodium hydroxide solution. In the latter case, it may be preferable that the carbon dioxide-containing effluent from the water condenser in the ODH scheme is first fed to the carbon dioxide removal unit, which is part of the ODH scheme, where the carbon dioxide is removed with an aqueous amine solution, and then fed to a carbon dioxide removal unit in a steam cracking circuit where the carbon dioxide is removed with an aqueous sodium hydroxide solution.

In addition, this invention relates to a chemical complex suitable for carrying out the above-described process for producing ethylene according to this invention, more specifically to a chemical complex that contains a steam cracking circuit and an oxidative dehydrogenation (ODH) circuit, where the steam cracking circuit comprises a steam cracker, a carbon dioxide removal, an optional dryer, a 1st separation plant, a 2nd separation plant, an optional acetylene hydrogenation unit, and a _C2 separation unit, each unit comprising one or more feed lines and one or more exhaust lines;

the ODH scheme comprises an ODH unit, a water condensing unit, an optional carbon dioxide removal unit, and an optional dryer unit, each unit comprising one or more feed lines and one or more exhaust lines;

the ODH circuit is integrated with the steam cracker circuit upstream of the optional acetylene hydrogenation unit and upstream of the C2 separation unit and no ODH plant feed line is integrated with the plant feed or outlet line in the steam cracker circuit, except that the steam cracker feed line and the supply line of the ODH plant may be integrated, and/or that the optional recycle line of the stream exiting the separation unit C2 and the supply line of the ODH plant may be integrated.

In particular, in the above chemical complex, the steam cracker circuit contains the following units, arranged in the following order, from the previous to the next: steam cracker, carbon dioxide removal unit, optional dryer, 1st separation plant, 2nd separation plant, optional an acetylene hydrogenation unit; and a _C2 separation unit. Additionally, a steam cracking circuit may comprise a cooling unit (cooler tower) and/or 1 or more compression units (compressors).

In addition, in particular, in the above-described chemical complex, the ODH scheme contains the following units, arranged in the following order, from the previous to the next: the ODH plant, the water condensation plant, the optional carbon dioxide removal plant, and the optional dryer plant. In addition, the ODH scheme may contain an oxygen removal unit and/or 1 or more compression units (compressors).

In the first embodiment of the above chemical complex, the 1st separation unit is a separation unit suitable for separating a stream containing C3+ hydrocarbons, C2 hydrocarbons, hydrogen, optionally carbon monoxide and optionally methane into a stream containing hydrogen, optionally carbon monoxide and optionally methane, and a stream containing C2+ hydrocarbons; and the 2nd separation unit is a separation unit suitable for separating a stream containing C2+ hydrocarbons into a stream containing C2 hydrocarbons and a stream containing C3+ hydrocarbons.

In the second embodiment of the above chemical complex, the 1st separation unit is a separation unit suitable for separating a stream containing C3+ hydrocarbons, C2 hydrocarbons, hydrogen, optionally carbon monoxide and optionally methane, into a stream containing C2 hydrocarbons, hydrogen, optionally monoxide carbon and optionally methane, and a stream containing C3+ hydrocarbons; and the 2nd separation unit is a separation unit suitable for separating a stream containing C2 hydrocarbons, hydrogen, optionally carbon monoxide and optionally methane into a stream containing hydrogen, optionally carbon monoxide and optionally methane, and a stream containing C2 hydrocarbons.

All features and embodiments of the invention described above with respect to the steam cracking circuit and the ODH circuit, including their installations used in the process of this invention, also apply to the corresponding circuits and installations in the chemical complex of this invention.

In particular, in the chemical complex of this invention, the effluent from the plant in the ODH circuit may be integrated with the feed line or effluent from the plant in the steam cracking circuit. In the context of this description, the integration of a line from the ODH scheme with a line from the steam cracking scheme in the chemical complex of this invention means that the two lines in question are connected.

In the chemical complex of this invention, the effluent from an ODH plant, which may be integrated with a feed line or effluent from a steam cracker, may be one or more of the following: a) a unit effluent water condensation; b) an effluent line from an optional carbon dioxide removal plant; and c) an effluent line from an optional dryer.

In the chemical plant of this invention, the effluent from the water condenser in the ODH circuit may be integrated with the feed line to the carbon dioxide removal plant in the steam cracker.

In the chemical complex of this invention, the effluent from the optional carbon dioxide removal plant in the ODH circuit may be integrated with the feed line of the optional dryer in the steam cracker circuit.

In the aforementioned first embodiment of the chemical complex of this invention, the effluent from the optional dryer in the ODH circuit may be integrated with the feed line of the 1st separation plant in the steam cracker circuit.

In the aforementioned second embodiment of the chemical complex of this invention, the effluent from the optional dryer in the ODH circuit may be integrated with the feed line of the 2nd separation plant in the steam cracker circuit.

The method and chemical complex of this invention is further illustrated in FIG. 1-3.

In FIG. 1 is a diagram of steam cracking. Said steam cracking circuit comprises a steam cracker 2, a carbon dioxide removal unit 4, a dryer 8, separating units 11, 15, 19 and 24, and an acetylene hydrogenation unit 22. All of these separation plants 11, 15, 19 and 24 are distillation columns. In addition, in FIG. 1 also shows an oxidative dehydrogenation (ODH) circuit integrated with said steam cracking circuit. Said ODH scheme comprises an ODH unit 31 and a water condensing unit 33 .

In FIG. 1 stream 1 containing ethane is fed to a steam cracker 2 operating under steam cracking conditions. The product stream 3 coming from the steam cracker 2 contains C3+ hydrocarbons, ethane, ethylene, acetylene, methane, hydrogen, carbon monoxide and carbon dioxide. Said stream 3 is fed to the carbon dioxide removal unit 4. The carbon dioxide removal agent is fed into the carbon dioxide removal unit 4 via stream 5. Said carbon dioxide removal agent may be an aqueous solution of a base such as sodium hydroxide or an amine. The carbon dioxide removal unit 4 may include a block in which carbon dioxide is removed with an aqueous amine solution and a further block in which carbon dioxide is removed with an aqueous sodium hydroxide solution. The carbon dioxide is removed with the water stream 6. The stream 7 coming from the carbon dioxide removal unit 4, which contains C3+ hydrocarbons, ethane, ethylene, acetylene, methane, hydrogen, carbon monoxide and water, is fed to the dryer 8. In the dryer 8, the water with stream 9. The stream 10 coming from the dryer 8, which contains C3+ hydrocarbons, ethane, ethylene, acetylene, methane, hydrogen and carbon monoxide, is fed into the separation plant 11.

In the 1st embodiment of the invention in the separation unit 11, stream 10 containing C3+ hydrocarbons, ethane, ethylene, acetylene, methane, hydrogen and carbon monoxide is separated into an upper stream 12 containing methane, hydrogen and carbon monoxide, and a lower stream 13, containing C3+ hydrocarbons, ethane, ethylene and acetylene. In said 1st embodiment, stream 13 is fed as stream 14 to separation plant 15. In separation plant 15, stream 14 is separated into an overhead stream 17 containing ethane, ethylene and acetylene and a bottom stream 16 containing C3+ hydrocarbons.

In the 2nd embodiment of the invention in the separation unit 11, stream 10 containing C3+ hydrocarbons, ethane, ethylene, acetylene, methane, hydrogen and carbon monoxide is separated into an upper stream 12 containing ethane, ethylene, acetylene, methane, hydrogen and carbon monoxide , and bottom stream 13 containing C3+ hydrocarbons. In said 2nd embodiment, stream 12 is fed as stream 18 to separation plant 19. In separation plant 19, stream 12 is separated into an overhead stream 20 containing methane, hydrogen and carbon monoxide and a bottom stream 21 containing ethane, ethylene and acetylene. .

The stream 17 containing ethane, ethylene and acetylene (the aforementioned 1st embodiment) or the stream 21 containing ethane, ethylene and acetylene (the aforementioned 2nd embodiment) is fed to the acetylene hydrogenation unit 22. In the acetylene hydrogenation unit 22, acetylene is hydrogenated with hydrogen stream 22a to ethylene to form stream 23 containing ethane and ethylene. Said stream 23 is fed to a separation unit 24 (separation unit C2), where stream 23 is separated into an overhead stream 25 containing ethylene and a bottom stream 26 containing ethane.

In addition, in FIG. 1 stream 28 containing ethane and stream 30 containing an oxidizing agent are fed to a unit 31 containing an ODH catalyst and operating under ODH conditions. The source of ethane fed to steam cracker 2 and ODH unit 31 may be the same or may be different sources. In the case of the same source, ethane from stream 1 can be fed through stream 29 and stream 28 to the ODH installation 31. The product stream 32 coming from the ODH plant 28 contains water, ethane, ethylene, acetylene, carbon monoxide, carbon dioxide and acetic acid. The specified stream 32 is served in the installation 33 of the water condensation. In the water condenser unit 33, water and acetic acid are removed by condensation with stream 34. In FIG. 1 stream 35 coming from the water condenser 33, which contains ethane, ethylene, acetylene, carbon monoxide and carbon dioxide, is fed to the carbon dioxide removal unit 4, which is part of the steam cracking scheme. In addition, prior to passing stream 35 to carbon dioxide removal unit 4, stream 35 may first be fed to another carbon dioxide removal unit (not shown in Fig.

- 12 042704 fig. 1), which is not part of the steam cracking scheme, and which can remove a relatively higher amount of carbon dioxide than in the carbon dioxide removal unit 4, for example, using an aqueous amine solution as a carbon dioxide removal agent. Typically, the effluent from an ODH unit has a relatively higher carbon dioxide content than the effluent from a steam cracker. In the latter case, the carbon dioxide removal plant 4 may only comprise a unit in which carbon dioxide is removed with an aqueous sodium hydroxide solution.

In addition, in FIG. 1 ethane from stream 26 may be recycled as stream 27. Stream 27a coming from stream 27 containing ethane may be fed to steam cracker 2. Stream 27b coming from the stream 27 and containing ethane, you can serve in the installation 31 ODH.

In FIG. 2 shows a steam cracking circuit and an oxidative dehydrogenation (ODH) circuit integrated with said steam cracking circuit. Said steam cracking scheme is identical to that shown in FIG. 1. In FIG. 2, the ODH scheme comprises an ODH unit 31, a water condensing unit 33, and a carbon dioxide removal unit 37.

The method shown in Fig. 2 is the same as the method shown in FIG. 1, except that the stream 35 from the water condenser 33, which is part of the ODH scheme, said stream 35 containing ethane, ethylene, acetylene, carbon monoxide and carbon dioxide, is not fed to the carbon dioxide removal unit 4, which is part of the steam cracking scheme and is fed as stream 36 to the carbon dioxide removal unit 37 which is part of the ODH scheme. The carbon dioxide remover is fed into the carbon dioxide remover 37 via stream 38. Said carbon dioxide remover may be an aqueous solution of a base such as sodium hydroxide or an amine. Carbon dioxide is removed with aqueous stream 39. In FIG. 2, stream 40 coming from carbon dioxide removal unit 37, containing ethane, ethylene, acetylene, carbon monoxide and water, is fed to dryer 8, which is part of the steam cracking circuit. In FIG. 2, the carbon dioxide removal unit 4 may only comprise a unit in which carbon dioxide is removed with an aqueous sodium hydroxide solution. In addition, in FIG. 2, the carbon dioxide removal unit 37 may include a block in which carbon dioxide is removed with an aqueous amine solution and a further block in which carbon dioxide is removed with an aqueous sodium hydroxide solution.

In FIG. 3 shows a steam cracking circuit and an oxidative dehydrogenation (ODH) circuit integrated with said steam cracking circuit. Said steam cracking scheme is identical to that shown in FIG. 1 and 2. In FIG. 3, the ODH scheme comprises an ODH unit 31, a water condensing unit 33, a carbon dioxide removal unit 37, and a drying unit 42.

The method shown in Fig. 3 is the same as the method shown in FIG. 2, except that the stream 40 coming from the carbon dioxide removal unit 37 which is part of the ODH scheme, said stream 40 containing ethane, ethylene, acetylene and carbon monoxide, is not fed to the dryer 8 which is part of the steam cracking, but is fed as stream 41 to dryer 42, which is part of the ODH scheme. In dryer 42, water is removed with stream 43. Stream 44 from the dryer contains ethane, ethylene, acetylene, and carbon monoxide. In the 1st embodiment of FIG. 3, which corresponds to the 1st embodiment described with respect to FIG. 1, stream 44 is sent as stream 45 to separation plant 11, which is part of the steam cracking circuit. In the 2nd embodiment of FIG. 3, which corresponds to the 2nd embodiment described with respect to FIG. 1, stream 44 is sent as stream 46 to separation plant 19, which is part of the steam cracking circuit.

In FIG. 1-3, the steam cracking circuit may include one or more compressors (not shown in FIGS. 1-3). One compressor may be located between the steam cracker 2 and the carbon dioxide removal unit 4. In FIG. 1, said compressor may be located between the steam cracker 2 and the merging point of streams 3 and 35. In addition, another compressor may be located between the carbon dioxide removal unit 4 and the dryer 8. In FIG. 2, said compressor may be located between the dryer 8 and the point where streams 7 and 40 merge.

In addition, in FIG. 1-3, the acetylene hydrogenation unit 22, which is part of the steam cracking circuit, may be located at a different location in the steam cracking circuit. In FIG. 1, the acetylene hydrogenation unit 22 may be located in any of the following positions (not shown in FIG. 1): 1) between the carbon dioxide removal unit 4 and the point where streams 3 and 35 are combined; 2) between the carbon dioxide removal unit 4 and the dryer 8; 3) between the drying plant 8 and the separating plant 11; 4) between separation plants 11 and 19 (only in the 2nd embodiment described in relation to FIG. 1). In FIG. 2, the acetylene hydrogenation unit 22 may be located in any of the following positions (not shown in FIG. 2): 1) between dryer 8 and the point where streams 7 and 40 combine; 2) between the drying plant 8 and the separating plant 11; 3) between separation plants 11 and 19 (only in the 2nd embodiment described in relation to FIG. 1). In FIG. 3 acetylene hydrogenation unit 22

-

Claims (10)

can be located in any of the following positions (not shown in Fig. 3): 1) between the separation plant 11 and the point of combining streams 10 and 45 (only in the 1st embodiment described in relation to Fig. 1); 2) between the separation plant 19 and the point where flows 18 and 46 merge (only in the 2nd embodiment described in relation to FIG. 1). In all these cases, it is advantageously not necessary to feed a separate hydrogen stream 22a to the acetylene hydrogenation unit 22, since hydrogen is still contained in said streams 3, 7, 10 and 18. In a further embodiment (not shown in FIGS. 1-3), a feed containing fresh ethane and optionally propane is fed to the next section of the steam cracking circuit, in particular line 10 leading to column 11 or line 14 leading to column 15, where the propane from the fresh ethane feed is predominantly removed along with C3+ hydrocarbons produced in the steam cracker, eliminating the need for a separate, additional depropanizer. In said additional embodiment, fresh ethane need not be fed directly to ODH reactor 31, and ethane recycle from line 27 may be sufficient. Said ethane recycle from line 27 still contains fresh ethane, i.e. fresh ethane fed to column 11 or 15 , which was neither subjected to steam cracking nor oxidative dehydrogenation (ODH) conditions. Thus, the fresh ethane fed in the above manner (i.e., indirectly via line 10 or line 14) to the ODH unit is obtained from a different source than the fresh ethane source used to feed ethane directly to the steam cracker. In addition, said ethane recycle from line 27 contains unreacted ethane, ie unreacted ethane leaving the steam cracker. The present invention is also applicable to a process in which, instead of processing an ethane-containing stream under steam cracking conditions, a naphtha-containing stream is subjected to steam cracking conditions in a steam cracker that is part of the steam cracking circuit of this invention. The above embodiments and preferences for ethane steam cracking apply equally to the above case in which the naphtha steam cracking circuit is integrated with the ODH circuit. In general, the stream resulting from the steam cracking of naphtha is fed to the cooling stage, which is cooling and removing heavy components. Such a cooling step can be included between units 2 and 4 in FIG. 1-3. CLAIM 1. A method for producing ethylene, which includes the following steps: processing the stream containing ethane or naphtha under steam cracking conditions in a steam cracker that is part of the steam cracking scheme to produce a stream containing unreacted ethane, ethylene, hydrogen, methane, carbon monoxide, carbon dioxide, and C3+ hydrocarbons; feeding a stream containing unreacted ethane, ethylene, hydrogen, methane, carbon monoxide, carbon dioxide, and C3+ hydrocarbons to a carbon dioxide removal unit that is part of the steam cracking circuit, and removing carbon dioxide from said stream in said carbon dioxide removal unit to obtain a stream containing unreacted ethane, ethylene, hydrogen, methane, carbon monoxide and C3+ hydrocarbons; treating the ethane-containing stream under oxidative dehydrogenation (ODH) conditions in an ODH unit that is part of the ODH scheme to produce a stream containing unreacted ethane, ethylene, water, carbon monoxide, and carbon dioxide; feeding a stream containing unreacted ethane, ethylene, water, carbon monoxide and carbon dioxide to a water condensing unit that is part of the ODH scheme, and removing water from said stream by condensing water in the water condensing unit to obtain a stream containing unreacted ethane, ethylene , carbon monoxide and carbon dioxide; feeding the effluent from the ODH circuit, which contains unreacted ethane and ethylene, to the steam cracker circuit at a position after the steam cracker; and where the stream containing unreacted ethane, ethylene, hydrogen, methane, carbon monoxide and C3+ hydrocarbons is separated in a separation unit, which is part of the steam cracking scheme, into a stream containing hydrogen, methane and carbon monoxide, and a stream containing C2+ hydrocarbons, and said C2+ hydrocarbons contain unreacted ethane, ethylene and C3+ hydrocarbons; the separated stream containing C2+ hydrocarbons is fed to the next separation plant, where said stream is separated into a stream containing C2 hydrocarbons, said C2 hydrocarbons containing unreacted ethane and ethylene, and a stream containing C3+ hydrocarbons; and the separated stream containing C2 hydrocarbons coming from the next separation unit is fed to the C2 separation unit, which is part of the steam cracking scheme, where the latter stream is separated into a stream containing ethylene and a stream containing unreacted ethane; And - 14 042704 where unreacted ethane and ethylene from the stream containing unreacted ethane and ethylene coming from the water condensation unit in the ODH scheme is fed to the C2 separation unit in the steam cracking scheme 2. A method for producing ethylene, comprising the following steps: processing the stream containing ethane or naphtha under steam cracking conditions in a steam cracker that is part of the steam cracking scheme to produce a stream containing unreacted ethane, ethylene, hydrogen, methane, carbon monoxide, carbon dioxide, and C3+ hydrocarbons; feeding a stream containing unreacted ethane, ethylene, hydrogen, methane, carbon monoxide, carbon dioxide, and C3+ hydrocarbons to a carbon dioxide removal unit that is part of the steam cracking circuit, and removing carbon dioxide from said stream in said carbon dioxide removal unit to obtain a stream containing unreacted ethane, ethylene, hydrogen, methane, carbon monoxide and C3+ hydrocarbons; treating the ethane-containing stream under oxidative dehydrogenation (ODH) conditions in an ODH unit that is part of the ODH scheme to produce a stream containing unreacted ethane, ethylene, water, carbon monoxide, and carbon dioxide; feeding a stream containing unreacted ethane, ethylene, water, carbon monoxide and carbon dioxide to a water condensing unit that is part of the ODH scheme, and removing water from said stream by condensing water in the water condensing unit to obtain a stream containing unreacted ethane, ethylene , carbon monoxide and carbon dioxide; feeding the effluent from the ODH circuit, which contains unreacted ethane and ethylene, to the steam cracker circuit at a position after the steam cracker; and where a stream containing unreacted ethane, ethylene, hydrogen, methane, carbon monoxide and C3+ hydrocarbons is separated in a separation unit that is part of a steam cracking scheme into a stream containing hydrogen, methane, carbon monoxide and C2 hydrocarbons, the C2 hydrocarbons containing unreacted ethane and ethylene, and a stream containing C3+ hydrocarbons; the separated stream containing hydrogen, methane, carbon monoxide and C2 hydrocarbons is fed to the next separating unit, where said stream is separated into a stream containing hydrogen, methane and carbon monoxide and a stream containing C2 hydrocarbons; the separated stream containing C2 hydrocarbons coming from the next separation unit is fed to the separation unit C2, which is part of the steam cracking scheme, where the latter stream is separated into a stream containing ethylene and a stream containing unreacted ethane; and where unreacted ethane and ethylene from the stream containing unreacted ethane and ethylene coming from the water condensation unit in the ODH circuit is fed to the C2 separation unit in the steam cracking circuit. 3. The method according to claim 1 or 2, characterized in that the ODH unit is supplied with ethane, which is obtained from one or more sources selected from the group consisting of: a) a fresh ethane source, which is used to supply ethane to the steam cracker ; b) another source of fresh ethane other than the specified first source referred to in paragraph a); and c) unreacted ethane from the effluent from the C2 separation unit. 4. The method according to claims 1, 2 or 3, characterized in that the stream coming from the steam cracker in the steam cracker circuit additionally contains acetylene; the stream coming from the ODH unit in the ODH circuit additionally contains acetylene; and said method includes the following additional step: an acetylene hydrogenation step in which a stream containing unreacted ethane, ethylene and acetylene is subjected to hydrogenation conditions in an acetylene hydrogenation unit, which is part of a steam cracking scheme, to convert acetylene to ethylene. 5. A chemical complex containing a steam cracking circuit and an oxidative dehydrogenation (ODH) circuit, in which the steam cracking circuit contains the following units in the following order in the flow direction: steam cracker, carbon dioxide removal unit, 1st separation plant, 2nd a separation plant and a C ₂ separation plant, each installation comprising one or more feed lines and one or more exhaust lines; the ODH circuit comprises the following units in the following order in the flow direction: an ODH unit and a condensing water unit, each unit comprising one or more supply lines and one or more outlet lines; the ODH circuit is integrated with the steam cracker circuit in the position upstream of the C2 separation unit and no ODH plant feed line is integrated with the plant feed or discharge line in the steam cracker circuit, except that the steam cracker feed line and the ODH plant feed line may be integrated, and/or that the recycle line of the stream leaving the separation unit C2 and the supply line of the ODH unit may be integrated; Where 1st separation unit is a separation unit suitable for separating a stream containing C3+ hydrocarbons, C2 hydrocarbons and hydrogen into a stream containing hydrogen and a stream containing C2+ hydrocarbons; And the 2nd separation unit is a separation unit suitable for separating a stream containing C2+ hydrocarbons into a stream containing C2 hydrocarbons and a stream containing C3+ hydrocarbons; and where: a) The effluent from the water condenser in the ODH scheme is integrated with the feed line to the carbon dioxide removal unit in the steam cracker. 6. A chemical complex containing a steam cracking circuit and an oxidative dehydrogenation (ODH) circuit, in which the steam cracking circuit contains the following units in the following order in the flow direction: steam cracker, carbon dioxide removal unit, 1st separation plant, 2nd a separation plant and a C ₂ separation plant, each installation comprising one or more feed lines and one or more exhaust lines; the ODH circuit comprises the following units in the following order in the flow direction: an ODH unit and a condensing water unit, each unit comprising one or more supply lines and one or more outlet lines; the ODH circuit is integrated with the steam cracker circuit in the position upstream of the C2 separation unit and no ODH plant feed line is integrated with the plant feed or discharge line in the steam cracker circuit, except that the steam cracker feed line and the ODH plant feed line may be integrated, and/or that the recycle line of the stream exiting the separation unit C2 and the supply line of the ODH unit can be integrated; and where the 1st separation unit is a separation unit suitable for separating a stream containing C3+ hydrocarbons, C2 hydrocarbons and hydrogen into a stream containing hydrogen and a stream containing C2+ hydrocarbons; And the 2nd separation unit is a separation unit suitable for separating a stream containing C2+ hydrocarbons into a stream containing C2 hydrocarbons and a stream containing C3+ hydrocarbons; and where: b) the steam cracker circuit further includes a drier and the ODH circuit further includes a carbon dioxide removal unit where the effluent from the carbon dioxide removal plant in the ODH circuit is integrated with the dryer feed line in the steam cracker circuit. 7. A chemical complex containing a steam cracking circuit and an oxidative dehydrogenation (ODH) circuit, in which the steam cracking circuit contains the following units in the following order in the flow direction: steam cracker, carbon dioxide removal unit, 1st separation plant, 2nd a separation plant and a C2 separation plant, each installation comprising one or more feed lines and one or more exhaust lines; the ODH circuit comprises the following installations in the following order in the direction of flow: an ODH installation and a water condensing installation, each installation having one or more supply lines and one or more exhaust lines; the ODH circuit is integrated with the steam cracker circuit in the position upstream of the C2 separation unit and no ODH plant feed line is integrated with the plant feed or discharge line in the steam cracker circuit, except that the steam cracker feed line and the ODH plant feed line may be integrated, and/or that the recycle line of the stream exiting the separation unit C2 and the supply line of the ODH unit can be integrated; Where The 1st separation unit is a separation unit suitable for separating a stream containing C3+ hydrocarbons, C2 hydrocarbons and hydrogen into a stream containing hydrogen and a stream containing C2+ hydrocarbons; And the 2nd separation unit is a separation unit suitable for separating a stream containing C2+ hydrocarbons into a stream containing C2 hydrocarbons and a stream containing C3+ hydrocarbons; and where: c) the ODH scheme additionally includes a drying plant and an effluent line from the dry - 16 042704 of the power plant in the ODH circuit is integrated with the feed line of the 1st separation plant in the steam cracking circuit. 8. A chemical complex containing a steam cracking circuit and an oxidative dehydrogenation (ODH) circuit, in which the steam cracking circuit contains the following units in the following order in the flow direction: steam cracking unit, carbon dioxide removal unit, 1st separation plant, 2nd a separation plant and a C ₂ separation plant, each installation comprising one or more feed lines and one or more exhaust lines; the ODH circuit comprises the following units in the following order in the flow direction: an ODH unit and a condensing water unit, each unit comprising one or more supply lines and one or more outlet lines; the ODH circuit is integrated with the steam cracker circuit in position before the C2 separation unit; no ODH unit feed line is integrated with a plant feed or outlet line in a steam cracker circuit, except that the steam cracker feed line and the ODH unit feed line may be integrated, and/or that the recycle line of the effluent from C2 separation plant, and ODH plant supply line can be integrated; and where The 1st separation unit is a separation unit suitable for separating a stream containing C3+ hydrocarbons, C2 hydrocarbons and hydrogen into a stream containing C2 hydrocarbons and hydrogen and a stream containing C3+ hydrocarbons; And the 2nd separation unit is a separation unit suitable for separating a stream containing C2 hydrocarbons and hydrogen into a stream containing hydrogen and a stream containing C2 hydrocarbons; and where a) The effluent from the water condenser in the ODH scheme is integrated with the feed line to the carbon dioxide removal unit in the steam cracker. 9. A chemical complex containing a steam cracking circuit and an oxidative dehydrogenation (ODH) circuit, in which the steam cracking circuit contains the following units in the following order in the flow direction: steam cracker, carbon dioxide removal unit, 1st separation plant, 2nd a separation plant and a C2 separation plant, each installation comprising one or more feed lines and one or more exhaust lines; the ODH circuit comprises the following installations in the following order in the direction of flow: an ODH installation and a water condensing installation, each installation having one or more supply lines and one or more exhaust lines; the ODH circuit is integrated with the steam cracker circuit in the position upstream of the C2 separation unit and no ODH plant feed line is integrated with the plant feed or discharge line in the steam cracker circuit, except that the steam cracker feed line and the ODH plant feed line may be integrated, and/or that the recycle line of the stream exiting the separation unit C2 and the supply line of the ODH unit can be integrated; and where The 1st separation unit is a separation unit suitable for separating a stream containing C3+ hydrocarbons, C2 hydrocarbons and hydrogen into a stream containing C2 hydrocarbons and hydrogen and a stream containing C3+ hydrocarbons; And the 2nd separation unit is a separation unit suitable for separating a stream containing C2 hydrocarbons and hydrogen into a stream containing hydrogen and a stream containing C2 hydrocarbons; and where b) the steam cracker circuit further includes a drier and the ODH circuit further includes a carbon dioxide removal unit, where the effluent from the carbon dioxide removal plant in the ODH circuit is integrated with the dryer feed line in the steam cracker circuit. 10. A chemical complex containing a steam cracking circuit and an oxidative dehydrogenation (ODH) circuit, in which the steam cracking circuit contains the following units in the following order in the flow direction: steam cracker, carbon dioxide removal unit, 1st separation plant, 2nd a separation plant and a C2 separation plant, each installation comprising one or more feed lines and one or more exhaust lines; the ODH scheme contains the following units in the following order in the direction of flow: an ODH unit and a condensing water unit, each unit containing one or more supply lines and -