A method and system for increasing the yield of light olefins

Abstract

The present invention discloses a method for increasing the production of low-carbon olefins and a system thereof, comprising the following steps: (1) sending light naphtha to a normal isomerization separation unit to produce normal components and non-normal components; (2) sending the non-normal components to a hydrocracking unit and separating them to obtain propane, normal butane and isobutane; (3) treating propane, normal butane and isobutane in different ways to obtain ethylene and propylene. The preparation method provided by the present invention greatly improves the yield of low-carbon olefins, significantly improves the utilization efficiency of naphtha, and realizes the rational allocation of resources.

Description

Technical Field

[0001] The present invention belongs to the field of low-carbon olefin preparation, and specifically relates to a process and system for increasing the yield of low-carbon olefins such as ethylene and propylene. Background Art

[0002] With the large-scale exploitation of oil resources, oil resources are becoming increasingly scarce. Therefore, how to optimize the use of oil resources has become an issue of increasing concern to many oil refining researchers. The capacity and output of ethylene and propylene production units are one of the most important indicators of the development level of the petrochemical industry. With the development of the national economy and the development of the petrochemical industry, the demand for ethylene and propylene has also increased dramatically.

[0003] At present, the main raw material for industrial production of light olefins is naphtha, which is a mixture of normal alkanes, isoalkanes, cycloalkanes and aromatics. The current processing of naphtha is to mix many components of different properties together for processing and production. The product yield obtained in this way is also relatively low, resulting in a waste of energy and resources. At the same time, the components in naphtha cannot be fully utilized. Summary of the invention

[0004] In response to the above technical problems, the present invention provides a method and system for increasing the yield of low-carbon olefins such as ethylene and propylene and aromatics, thereby achieving comprehensive utilization of light naphtha while maximizing the production of ethylene and propylene products.

[0005] The technical solution of the present invention is as follows:

[0006] In one aspect, the present invention provides a method for increasing the production of light olefins and aromatics, the method comprising the following steps:

[0007] (1) sending light naphtha to a normal isomerization separation unit to produce normal components and non-normal components;

[0008] (2) sending the non-normal components to a hydrocracking unit, and further separating the hydrocracking products to obtain refinery dry gas, propane, normal butane and isobutane, respectively; and / or, sending the non-normal components to an aromatization unit, and further separating the aromatization products to obtain refinery dry gas, propane, normal butane and isobutane, and C5+ components, respectively;

[0009] (3) sending the propane to a propane dehydrogenation unit to produce propylene, sending the n-butane to a steam cracking unit to produce ethylene and propylene; sending the isobutane to a normalization unit to produce n-butane, and sending the produced n-butane to a steam cracking unit to produce ethylene and propylene;

[0010] (4) The refinery dry gas is sent to a cryogenic separation unit to produce ethane and fuel gas containing C1, and the produced ethane is sent to a steam cracking unit to produce ethylene.

[0011] Based on the above scheme, preferably, the light naphtha includes C5-C6 alkanes; the normal components include normal C5-C6 alkanes; and the non-normal components include isomeric C5-C6 alkanes.

[0012] Based on the above scheme, preferably, the normal components produced in step (1) are sent to a steam cracking unit to produce ethylene and propylene, and the C1 fuel gas includes methane.

[0013] Based on the above scheme, preferably, the C5+ components include benzene, toluene, and C8-C10 aromatics.

[0014] Based on the above scheme, preferably, the refinery dry gas includes C1-C2 components.

[0015] Based on the above scheme, preferably, the light naphtha is separated into normal isomers by distillation or adsorption.

[0016] Based on the above scheme, preferably, the raw material of the cryogenic separation unit also includes dry gas produced by other equipment in the refinery; the raw material of the normalization unit also includes isomerized C4 produced by other equipment in the refinery; the raw material of the propane dehydrogenation unit also includes propane produced by other equipment in the refinery, and the other equipment in the refinery refers to the refinery equipment other than the equipment used for the normal-isomerization separation unit and the aromatization unit.

[0017] Based on the above scheme, preferably, the other units of the refinery include: atmospheric and vacuum distillation unit, aviation kerosene hydrogenation unit, wax oil hydrogenation unit (including cracking), diesel hydrogenation unit (including cracking), residue oil hydrogenation unit (including cracking), reforming unit, disproportionation unit, alkylation unit, and MTBE unit.

[0018] In another aspect, the present invention provides a system for use in the above method, the system comprising a normal isomerization separation unit, a hydrocracking unit, an aromatization unit, a normalization unit, a steam cracking unit, a propane dehydrogenation unit, and a cryogenic separation unit;

[0019] The normal isomerization separation unit comprises a light naphtha feed port, a normal component outlet and an isomerization component outlet; the isomerization component outlet is respectively connected to the feed ports of the hydrocracking unit and the aromatization unit;

[0020] The hydrocracking device comprises a hydrocracking unit and a cracking product separation unit which are connected in sequence; the cracking product separation unit comprises a refinery dry gas outlet 1, a propane outlet 1, a normal butane outlet 1 and an isobutane outlet 1;

[0021] The aromatization device comprises an aromatization unit and an aromatization product separation unit which are connected in sequence; the aromatization product separation unit comprises a refinery dry gas outlet 2, a propane outlet 2, a normal butane outlet 2, an isobutane outlet 2 and a C5+ component outlet;

[0022] The propane outlet 1 and the propane outlet 2 are connected to the feed inlet of the propane dehydrogenation device;

[0023] The n-butane outlet 1 and n-butane outlet 2 are connected to the feed inlet of the steam cracking device;

[0024] The isobutane outlet 1 and the isobutane outlet 2 are connected to the feed port of the normalization device, and the discharge port of the normalization device is connected to the feed port of the steam cracking device;

[0025] The refinery dry gas outlet 1 and the refinery dry gas outlet 2 are connected to the feed inlet of the cryogenic separation device; the cryogenic separation device also includes a fuel gas outlet and an ethane outlet; the ethane outlet is connected to the feed inlet of the steam cracking device.

[0026] Based on the above scheme, preferably, the system also includes other refinery devices, and the discharge ports of the other refinery devices are connected to the feed ports of one or more devices among the cryogenic separation device, the normalization device, and the propane dehydrogenation device; the other refinery devices include aviation kerosene hydrogenation units, wax oil hydrocracking units, diesel hydrocracking units, residue oil hydrocracking units, reforming units, disproportionation units, alkylation units, and MTBE units.

[0027] In the above-mentioned devices, the normal isomer separation device can adopt the device used in the prior art to realize the normal isomer separation of light naphtha; the hydrocracking device can adopt the device used in the prior art to realize the hydrocracking of non-normal components in light naphtha and further separate the hydrocracking products; the steam cracking device can adopt the device used in the prior art to steam crack low-carbon hydrocarbons into ethylene; the aromatization device can adopt the device used in the prior art to aromatize non-normal components and further separate the aromatized products; the normalization device can adopt the device used in the prior art to normalize isobutane; the propane dehydrogenation device can adopt the device used in the prior art to dehydrogenate propane to produce propylene; the cryogenic separation device can adopt the device used in the prior art to separate the dry gas produced by the refinery into ethane and C1 fuel gas through a cryogenic separation process. Other devices of the refinery can all be devices in the prior art.

[0028] Beneficial Effects

[0029] The present invention first separates normal alkanes and non-normal alkanes from light naphtha, and directly uses normal alkanes as a raw material for steam cracking, thereby improving the yield of ethylene; at the same time, the non-normal alkane components are further separated into refinery dry gas, propane, normal butane and isobutane through a hydrocracking reaction; wherein, propane is used to prepare propylene through a dehydrogenation reaction, thereby improving the yield of propylene; isobutane is converted into normalized ...

[0030] The present invention separates C5-C6 isoparaffins from light naphtha and performs aromatization on them, and can produce C5+ products while further separating refinery dry gas, propane, normal butane and isobutane, so that various components in naphtha can be fully and effectively utilized and the yield of light naphtha aromatics can be improved.

[0031] The present invention separates C5-C6 isoparaffins from light naphtha and performs hydrocracking, thereby increasing the saturation of components and reducing the content of aromatics, which is beneficial to increasing the yield of low-carbon olefins in the steam cracking process.

[0032] The process combination provided in this application considers the comprehensive utilization of naphtha from a molecular perspective, and separates the components of the mixture from a molecular perspective, that is, from the specific requirements of different products for raw material molecules, so as to make the best use of them, thereby greatly improving the yield of low-carbon olefins and aromatics, significantly improving the utilization efficiency of naphtha, and realizing the rational allocation of resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The overall process flow chart for increasing the yield of light olefins and aromatics provided by the present invention;

[0034] Figure 2 A process flow chart for increasing the yield of light olefins provided in Example 2 of the present invention;

[0035] Figure 3 A process flow chart for increasing the yield of light olefins and aromatics provided in Example 3 of the present invention;

[0036] Figure 4 A process flow chart for increasing the yield of light olefins provided in Example 4 of the present invention. DETAILED DESCRIPTION

[0037] The present invention is further described in detail below in conjunction with the accompanying drawings.

[0038] In the following examples and comparative examples, the light olefin yield is calculated according to the following formula:

[0039] Ethylene yield (weight %) = weight of ethylene in steam cracking reaction product / total weight of light naphtha × 100%;

[0040] Propylene yield (weight %) = (weight of propylene in steam cracking reaction product + weight of propylene in propane dehydrogenation reaction product) / total weight of light naphtha × 100%;

[0041] Yield of each C5+ component (weight %) = weight of each C5+ component in the aromatization reaction product ÷ total weight of light naphtha × 100%.

[0042] Example 1

[0043] A method and system for increasing the yield of light olefins, such as Figure 1 As shown, the system includes a normal isomerization separation unit, a hydrocracking unit, an aromatization unit, a normalization unit, a steam cracking unit, a propane dehydrogenation unit and a cryogenic separation unit; the normal isomerization separation unit includes a light naphtha feed port, a normal component outlet and an isomerization component outlet; the isomerization component outlet is connected to the feed ports of the hydrocracking unit and the aromatization unit respectively; the hydrocracking unit includes a hydrocracking unit and a cracking product separation unit connected in sequence; the cracking product separation unit includes a refinery dry gas outlet 1, a propane outlet 1, a normal butane outlet 1 and an isobutane outlet 1; the aromatization unit includes an aromatization unit and an aromatization product separation unit connected in sequence; the aromatization product separation unit includes a refinery dry gas outlet 2, a propane outlet 2, a normal butane outlet 2, an isobutane outlet 2 and a C5+ component outlet;

[0044] The propane outlet 1 and the propane outlet 2 are connected to the feed inlet of the propane dehydrogenation device;

[0045] The n-butane outlet 1 and n-butane outlet 2 are connected to the feed inlet of the steam cracking device;

[0046] The isobutane outlet 1 and the isobutane outlet 2 are connected to the feed port of the normalization device, and the discharge port of the normalization device is connected to the feed port of the steam cracking device; the refinery dry gas outlet 1 and the refinery dry gas outlet 2 are connected to the feed port of the cryogenic separation device; the cryogenic separation device also includes a fuel gas outlet and an ethane outlet; the ethane outlet is connected to the feed port of the steam cracking device.

[0047] The above method comprises the following steps:

[0048] (1) sending light naphtha to a normal isomerization separation unit to produce normal components and non-normal components;

[0049] (2) sending part of the non-normal components to a hydrocracking unit, and further separating the hydrocracking products to obtain refinery dry gas, propane, normal butane and isobutane respectively; and sending another part of the non-normal components to an aromatization unit, and further separating the aromatization products to obtain refinery dry gas, propane, normal butane and isobutane, and C5+ components respectively;

[0050] (3) sending the propane to a propane dehydrogenation unit to produce propylene, sending the n-butane to a steam cracking unit to produce ethylene and propylene; sending the isobutane to a normalization unit to produce n-butane, and sending the produced n-butane to a steam cracking unit to produce ethylene and propylene;

[0051] (4) sending the refinery dry gas to a cryogenic separation unit to produce ethane and a fuel gas containing C1, and the produced ethane is sent to a steam cracking unit to produce ethylene;

[0052] (5) The normal components produced in step (1) are sent to a steam cracking unit to produce ethylene and propylene.

[0053] In the above steps, the temperature of the hydrocracking unit is 330-360° C., and the pressure is 6-8 MPa (gauge pressure); the temperature of the aromatization unit is 380-400° C., and the pressure is 0.4-1.0 MPa (gauge pressure).

[0054] In the above steps, the content of each component is as follows: the proportion of C5-C6 alkanes in light naphtha is 99%. After normal isomerization separation, the proportions of normal C5-C6 and non-normal C5-C6 in C5-C6 alkanes are 35% and 65%, respectively, of which 30% of the non-normal C5-C6 enters the hydrocracking unit, and 35% of the non-normal C5-C6 enters the aromatization unit.

[0055] After passing through the hydrocracking unit and separation, refinery dry gas, propane, normal butane and isobutane account for 6%, 31%, 29% and 34% of the non-normal C5-C6 entering the hydrocracking unit respectively, and ethane separated by deep cooling accounts for 82% of the refinery dry gas.

[0056] After aromatization unit and separation, the proportion of refinery dry gas, propane, normal butane, isobutane and C5+ components in non-normal C5-C6 are 5%, 49%, 11%, 11% and 24% respectively. The proportion of ethane separated by deep cold is 80% of refinery dry gas.

[0057] Among the obtained products, the total ethylene yield is 35%, of which the ethylene yield from normal C5-C6 is about 18%, and the ethylene yield from isomerized C5-C6 is about 17%.

[0058] The total yield of propylene in the obtained product is 40%, of which the yield of propylene derived from normal C5-C6 is about 9%, and the yield of propylene derived from isomerized C5-C6 is about 31%.

[0059] Among the obtained products, the total yield of propylene is 43%, of which the yield of propylene produced by steam cracking of normal C5-C6 is about 9%, the yield of propylene produced by propane dehydrogenation is about 30.5%, and the yield of propylene produced by steam cracking after normalization of normal butane and isobutane is about 3.5%.

[0060] Among the obtained products, the total yield of C5+ components is 14%, among which the total yield of benzene and toluene is 8.4%, and the total yield of C8-C10 aromatic hydrocarbons is 2.8%.

[0061] Example 2

[0062] A method and system for increasing the yield of light olefins, such as Figure 2 As shown, the system includes a normal isomer separation unit, a hydrocracking unit, a normalization unit, a steam cracking unit, a propane dehydrogenation unit and a cryogenic separation unit; the normal isomer separation unit includes a light naphtha feed port, a normal component outlet and an isomer component outlet; the isomer component outlet is connected to the feed port of the hydrocracking unit; the hydrocracking unit includes a hydrocracking unit and a cracking product separation unit connected in sequence; the cracking product separation unit includes a refinery dry gas outlet 1, a propane outlet 1, a normal butane outlet 1 and an isobutane outlet 1; the propane outlet 1 is connected to the feed port of the propane dehydrogenation unit; the normal butane outlet 1 is connected to the feed port of the steam cracking unit; the isobutane outlet 1 is connected to the feed port of the normalization unit, and the outlet of the normalization unit is connected to the feed port of the steam cracking unit. The refinery dry gas outlet is connected to the feed inlet of the cryogenic separation device; the cryogenic separation device also includes a fuel gas outlet and an ethane outlet; the ethane outlet is connected to the feed inlet of the steam cracking device.

[0063] The above method comprises the following steps:

[0064] (1) sending light naphtha to a normal isomerization separation unit to produce normal components and non-normal components;

[0065] (2) sending the non-normal components to a hydrocracking unit, and further separating the hydrocracking products to obtain refinery dry gas, propane, normal butane and isobutane, respectively;

[0066] (3) sending the propane to a propane dehydrogenation unit to produce propylene, sending the n-butane to a steam cracking unit to produce ethylene and propylene; sending the isobutane to a normalization unit to produce n-butane, and sending the produced n-butane to a steam cracking unit to produce ethylene and propylene;

[0067] (4) sending the normal components produced in step (1) to a steam cracking unit to produce ethylene and propylene;

[0068] (5) The refinery dry gas produced in step (2) is sent to a cryogenic separation unit to produce ethane and a fuel gas containing C1, and the ethane is sent to a steam cracking unit to produce ethylene.

[0069] In the above steps, the temperature of the hydrocracking unit is 330-360°C and the pressure is 6-8MPa (gauge pressure).

[0070] In the above steps, the content of each component is as follows: the proportion of C5-C6 alkanes in light naphtha is 98%, and after normal isomerization separation, the proportions of normal C5-C6 and non-normal C5-C6 in C5-C6 alkanes are 34% and 66%, respectively; after passing through the hydrocracking unit and separation, the proportions of refinery dry gas, propane, normal butane and isobutane in non-normal C5-C6 are 6%, 30%, 30% and 34%, respectively, and the proportion of ethane separated by deep cold in refinery dry gas is 80%.

[0071] Among the obtained products, the total ethylene yield is 44.5%, among which the ethylene yield produced by steam cracking of normal C5-C6 is about 18%, the yield produced by steam cracking of ethane obtained by deep cold separation of refinery dry gas is about 3.5%, and the ethylene yield produced by steam cracking of normalized normal-butane and isobutane is about 23%.

[0072] Among the obtained products, the total propylene yield is 36.5%, of which the propylene yield produced by normal C5-C6 steam cracking is about 9.5%, the propylene yield produced by propane dehydrogenation is about 19%, and the propylene yield produced by normal butane and isobutane steam cracking is about 8%.

[0073] Example 3

[0074] A method and system for increasing the yield of light olefins and aromatics, such as Figure 3 As shown, the system used is as follows:

[0075] The system comprises a normal isomerization separation device, an aromatization device, a normalization device, a steam cracking device, a propane dehydrogenation device and a cryogenic separation device; the normal isomerization separation device comprises a light naphtha feed port, a normal component outlet and an isomerization component outlet; the isomerization component outlet is connected to the feed port of the aromatization device; the aromatization device comprises an aromatization unit and an aromatization product separation unit which are connected in sequence; the aromatization product separation unit comprises a refinery dry gas outlet 2, a propane outlet 2, a normal butane outlet 2, an isobutane outlet 2 and a C5+ component outlet; the propane outlet 2 is connected to the feed port of the propane dehydrogenation device; the normal butane outlet 2 is connected to the feed port of the steam cracking device; the isobutane outlet 2 is connected to the feed port of the normalization device, and the outlet of the normalization device is connected to the feed port of the steam cracking device.

[0076] The refinery dry gas outlet 2 is connected to the feed inlet of the cryogenic separation device; the cryogenic separation device also includes a fuel gas outlet and an ethane outlet; the ethane outlet is connected to the feed inlet of the steam cracking device.

[0077] The above method comprises the following steps:

[0078] (1) sending light naphtha to a normal isomerization separation unit to produce normal components and non-normal components;

[0079] (2) sending the non-normal components to an aromatization unit, and further separating the aromatization products to obtain refinery dry gas, propane, normal butane, isobutane and C5+ components, respectively;

[0080] (3) sending the propane to a propane dehydrogenation unit to produce propylene, sending the n-butane to a steam cracking unit to produce ethylene and propylene; sending the isobutane to a normalization unit to produce n-butane, and sending the produced n-butane to a steam cracking unit to produce ethylene and propylene;

[0081] (4) sending the normal components produced in step (1) to a steam cracking unit to produce ethylene and propylene;

[0082] (5) The refinery dry gas produced in step (2) is sent to a cryogenic separation unit to produce ethane and a fuel gas containing C1, and the ethane is sent to a steam cracking unit to produce ethylene.

[0083] In the above steps, the temperature of the aromatization unit is 380-400° C., and the pressure is 0.4-1.0 MPa (gauge pressure).

[0084] In the above steps, the content of each component is as follows: the proportion of C5-C6 alkanes in light naphtha is 98%, and after normal isomerization separation, the proportions of normal C5-C6 and non-normal C5-C6 in C5-C6 alkanes are 34% and 66%, respectively; after aromatization unit and separation, the proportions of refinery dry gas, propane, normal butane, isobutane and C5+ components in non-normal C5-C6 are 5%, 50%, 10%, 10% and 25%, respectively, and the proportion of ethane separated by deep cooling in refinery dry gas is 80%.

[0085] Among the obtained products, the total ethylene yield is 27%, among which the ethylene yield produced by steam cracking of normal C5-C6 is about 18%, the yield produced by steam cracking of ethane obtained by deep cold separation of refinery dry gas is about 3%, and the ethylene yield produced by steam cracking of normalized n-butane and isobutane is about 6%.

[0086] Among the obtained products, the total yield of propylene is 43%, of which the yield of propylene produced by steam cracking of normal C5-C6 is about 9%, the yield of propylene produced by propane dehydrogenation is about 30.5%, and the yield of propylene produced by steam cracking after normalization of normal butane and isobutane is about 3.5%.

[0087] Among the obtained products, the total yield of C5+ components is 25%, among which the total yield of benzene and toluene is 15%, and the total yield of C8-C10 aromatic hydrocarbons is 5%.

[0088] Example 4

[0089] The difference from Example 2 is that step (5) is not included;

[0090] Among the obtained products, the total yield of ethylene was 41%, and the total yield of propylene was 36.5%.

[0091] Comparative Example 1

[0092] The difference from Example 1 is that the light naphtha is directly fed into the steam cracking unit to produce ethylene and propylene;

[0093] Among the obtained products, the yield of ethylene was 32% and the yield of propylene was 13%.

Claims

1. A method for preparing light olefins, characterized in that: The method comprises the following steps: (1) sending light naphtha to a normal isomerization separation unit to produce normal components and non-normal components; (2) sending the non-normal components to a hydrocracking unit, and further separating the hydrocracking products to obtain propane, normal butane and isobutane, respectively; (3) sending the propane to a propane dehydrogenation unit to produce propylene, sending the n-butane to a steam cracking unit to produce ethylene and propylene; sending the isobutane to a normalization unit to produce n-butane, and sending the produced n-butane to a steam cracking unit to produce ethylene and propylene; The light naphtha includes C5-C6 alkanes; the normal components include normal C5-C6 alkanes; the non-normal components include isomeric C5-C6 alkanes; The normal components produced in step (1) are sent to a steam cracking unit to produce ethylene and propylene; The system used in the method includes a normal isomerization separation unit, a hydrocracking unit, a normalization unit, a steam cracking unit, and a propane dehydrogenation unit; The normal isomerization separation unit comprises a light naphtha feed port, a normal component outlet and an isomerization component outlet; the isomerization component outlet is respectively connected to the feed ports of the hydrocracking unit and the aromatization unit; The hydrocracking device comprises a hydrocracking unit and a cracking product separation unit which are connected in sequence; the cracking product separation unit comprises a propane outlet, a normal butane outlet and an isobutane outlet; The propane outlet is connected to the feed inlet of the propane dehydrogenation device; The n-butane outlet is connected to the feed inlet of the steam cracking device; The isobutane outlet is connected to the feed port of the normalization device, and the discharge port of the normalization device is connected to the feed port of the steam cracking device The light naphtha is separated into normal isomers by distillation or adsorption.

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