CN111116290B

CN111116290B - Energy expanding method for olefin cracking device

Info

Publication number: CN111116290B
Application number: CN201811275662.4A
Authority: CN
Inventors: 金鑫; 卢和泮
Original assignee: China Petroleum and Chemical Corp; Sinopec Shanghai Research Institute of Petrochemical Technology
Current assignee: China Petroleum and Chemical Corp; Sinopec Shanghai Research Institute of Petrochemical Technology
Priority date: 2018-10-30
Filing date: 2018-10-30
Publication date: 2023-04-07
Anticipated expiration: 2038-10-30
Also published as: CN111116290A

Abstract

The invention relates to an energy expansion method for an olefin cracking device, which mainly solves the problems that the production capacity of the olefin cracking device in the prior art has a bottleneck and the olefin yield is low. The invention adopts the technical proposal that the byproduct carbon IV of the original olefin cracking device is sent into a newly-built olefin cracking reactor, the obtained reaction product is sent into a newly-built depropanizing tower for separation, the crude propylene product with increased yield is extracted from the top of the newly-built depropanizing tower, the kettle liquid of the newly-built depropanizing tower and the byproduct carbon-containing five-component gasoline of the original device are converged and sent into the newly-built depentanizing tower, the byproduct crude gasoline is extracted from the kettle of the newly-built depentanizing tower, and the carbon IV at the top of the newly-built depentanizing tower is taken as a circulating material to be converged with the byproduct carbon IV of the original device, thereby better solving the problems and being applicable to the industrial production of low-carbon olefin.

Description

Energy expanding method for olefin cracking device

Technical Field

The invention relates to an energy expanding method for an olefin cracking device.

Technical Field

Ethylene plants, catalytic cracking plants and methanol-to-olefins plants all produce a large amount of by-products of hydrocarbons containing four carbon atoms and five carbon atoms, of which more than 60% are olefins. The catalytic cracking production of low-carbon olefins such as ethylene and propylene by using the byproduct hydrocarbons as raw materials is an important way for improving the device benefit. The olefin catalytic cracking technology consists of an olefin catalytic cracking reaction technology and a product separation technology. The core of the reaction technology is the development of a catalyst and a reactor, and the core of the separation technology is the separation process which is designed with reasonable flow and is economically feasible according to the distribution characteristics of the olefin cracking products.

The olefin catalytic cracking technology which is industrially applied at present in China comprises OCC complete technology of China Shanghai petrochemical industry research institute and OCT technology of LUMMUS company. The OCC technology adopts a ZSM-5 molecular sieve catalyst to convert the C-C pentacene into ethylene and propylene with high selectivity and to produce a small amount of C-C and naphtha as byproducts. The OCT technique converts ethylene and carbon tetraolefins to propylene. With the recent decrease in propylene prices, the OCC technology of the china petrochemical shanghai petrochemical institute has gained wide attention. The technology improves the overall economy of the methanol-to-olefin device by converting the C-pentaolefin with low added value into ethylene and propylene, and has the advantages of simple device flow, low investment and high benefit.

CN1704387 discloses a catalyst for preparing propylene and ethylene by cracking olefin. The catalyst adopts a ZSM-5 molecular sieve with the molar ratio of 40-80% of silicon to aluminum (SiO 2/Al2O 3) being 60-1000, a binder and rare earth loaded by the ZSM-5 molecular sieve with the weight being 0.01-5% as the catalyst, has the advantages of good high-temperature hydrothermal stability, long catalyst regeneration period and the like, and can be used for industrial production of propylene and ethylene by olefin cracking.

CN1915924 discloses a method for producing propylene by catalytic cracking of C4 olefin, which mainly solves the problem that molecular sieve catalyst binder influences the conversion rate, selectivity and space velocity performance of propylene product in the prior art. The method adopts a ZSM molecular sieve catalyst with high crystallinity, and the reaction temperature is 400-600 ℃, the reaction pressure is 0-0.15 MPa, and the weight space velocity is 2-50 hours ^-1 The catalyst is contacted under the condition to generate catalytic cracking to produce the propylene, and the method can be used for industrial production of propylene by cracking C4 olefins.

CN1962579 relates to a separation method of a carbon-containing olefin cracking product, which comprises the steps of compressing the carbon-containing olefin cracking product to 1.0-4.0 MPa, entering the carbon-containing olefin cracking product into a first separation tower, obtaining ethylene at the tower top, entering tower kettle liquid into a second separation tower, obtaining fractions below C5 and C5 at the tower top, and obtaining fractions above C6 at the tower bottom; c5 and fractions below C5 enter a third separation tower, and C3 fractions obtained from the tower top enter a fourth separation tower; the tower bottom liquid is C4 and C5 fractions; the side line of the fourth separation tower is extracted to obtain propylene with the weight concentration of 90-99 percent, and the tower kettle obtains propane with the weight concentration of 80-95 percent. 20-80 wt% of C4 and C5 fractions separated from the tower bottom of the third separation tower are recycled as cracking reaction raw materials.

Because the conversion of the carbon four-carbon five-hydrocarbon in the olefin catalytic cracking device into the ethylene and propylene with high added value has high selectivity and good economic benefit, the needs of further improving the yield of the diene and improving the productivity are urgent. The problems that the production capacity of an olefin cracking device is bottleneck and the yield of olefin is low exist in the prior art, and the method is used for specifically solving the problems.

Disclosure of Invention

The invention aims to solve the technical problems that the production capacity of an olefin cracking device in the prior art has a bottleneck, the olefin yield is low, and byproducts, particularly C5-C6 byproducts are more, and provides a novel energy expansion method for the olefin cracking device. The method has the advantages of high production capacity of the olefin cracking device, low carbon olefin yield and few byproducts, particularly C5-C6 byproducts, is particularly suitable for energy expansion transformation of the conventional olefin cracking device, and does not influence the conventional capacity before the energy expansion is finished.

In order to solve the problems, the technical scheme adopted by the invention is as follows: an energy expanding method for an olefin cracking device comprises the following steps: feeding the byproduct carbon four of the original olefin cracking device into a newly-built olefin cracking reactor, feeding the obtained reaction product into a newly-built depropanizing tower for separation, extracting a crude propylene product for increasing yield from the top of the newly-built depropanizing tower, converging the bottom liquid of the newly-built depropanizing tower and the byproduct carbon-containing five-component gasoline of the original olefin cracking device, feeding the converged mixture into the newly-built depentanizing tower, extracting crude gasoline from the bottom of the newly-built depentanizing tower, obtaining a byproduct carbon four-carbon five-stream from the top of the newly-built depentanizing tower, and converging at least part of the carbon four-carbon five-stream as a circulating material with the byproduct carbon four of the original olefin cracking device.

In the technical scheme, the raw material of the crude olefin cracking device is a hydrocarbon material flow containing carbon, four carbon and five carbon, wherein the total mass content of the carbon, four carbon and five carbon olefin is 60-95 WT%.

In the above technical scheme, the raw material of the crude olefin cracking device is a hydrocarbon material stream containing carbon, four carbon and five which is a byproduct of a methanol to olefin device.

In the technical scheme, the newly-built olefin cracking reactor adopts a catalyst with cracking capability on C-pentaalkane.

In the technical scheme, the design treatment capacity of the newly-built olefin cracking reactor is not more than that of the original olefin cracking reactor.

In the above technical solution, the ratio of the carbon four-carbon five stream as the recycle stream is at least 70%, and the preferable ratio of the recycle stream is at least 90%.

In the technical scheme, the circulation ratio of the newly-built olefin cracking reactor is 2.0-5.0.

In the technical scheme, the reaction product of the newly-built olefin cracking reactor is pressurized to 1.0-2.0 MPA and then sent into a newly-built depropanizer.

In the technical scheme, the operating pressure of the newly-built depropanizer is 0.8-1.8 MPA.

In the technical scheme, the operating pressure of the newly-built depentanizer is 0.3-0.8 MPA.

The original olefin cracking device can adopt the olefin cracking catalyst and the process flow of the prior art to produce ethylene and propylene, and simultaneously produce four carbon components and five carbon components as byproducts, and also can be a process flow depending on the prior olefin separation device, wherein the raw materials are converted into reaction products by a reactor of the original olefin cracking device and then are sent into a compressor to be pressurized to 1.0-4.0 MPa, then the reaction products enter a depropanizing tower to obtain crude propylene products at the top of the tower, the four carbon components and heavier components are obtained at the bottom of the tower, the crude propylene products enter the prior olefin separation device to separate the ethylene and the propylene, the four carbon components and heavier components are sent into a depentanizing tower to separate six carbon components and heavier components, and most of the four carbon components and five carbon components are recycled to the reactor.

By adopting the method, the byproduct carbon four of the original olefin cracking device and the carbon five components contained in the byproduct naphtha are further converted into ethylene and propylene in the newly-built olefin cracking device, thereby improving the yield of the ethylene and the propylene. The yield of the low-carbon olefin is further improved by adopting a process with a high circulation ratio and a catalyst with strong cracking capability on the C-V alkane. For cracking raw materials with higher content of C, E and V olefins from upstream, the method can improve the yield of crude propylene by over 35 percent and improve the yield of diene of the whole device by over 26 percent. For cracking raw materials with high content of C, C and C pentaalkanes, the method has more advantages, can improve the yield of crude propylene by more than 50 percent, and improve the yield of diene by more than 40 percent.

In conclusion, the method can effectively solve the problems of bottleneck in the production capacity of the olefin cracking device and low olefin yield, and obtains better technical effects.

Drawings

FIG. 1 is a schematic flow diagram of the process of the present invention.

In FIG. 1, 1 is an upstream olefin cracking feedstock; 2 is crude propylene product of a crude olefin cracking device; 3 is a byproduct carbon IV of the original olefin cracking device; 4, the by-product of the original device is the gasoline containing carbon and five components; 5, newly building an olefin cracking reactor; 6, establishing a reaction product of an olefin cracking reactor; 7 is a reaction product pressurized by a compressor; 8 is the depropanizer kettle liquid; 9 is the depentanizer feed; 10 is a depentanizer liftout material; 11 is the by-product crude gasoline, 12 is the purge gas, 13 is the carbon four carbon five cycle material, and 14 is the crude propylene product for increasing the yield.

In FIG. 1, A is a crude olefin cracking apparatus, B is a newly-built olefin cracking reactor, C is a compressor, D is a depropanizer, and E is a depentanizer.

The process flow is illustrated as follows: the upstream olefin cracking raw material is converted into a crude propylene product, a byproduct carbon four and a byproduct carbon-containing five-component gasoline in an original olefin cracking device. And the byproduct carbon four and the circulating carbon four-five from the top of the newly-built depentanizer are converged and then sent into a newly-built olefin cracking reactor together for olefin cracking reaction to generate a reaction product rich in ethylene and propylene. The reaction product is pressurized by a compressor and then sent to a depropanizer to separate a crude propylene product 14, which is the increased capacity. The depropanizing tower liquid and the by-product gasoline containing five carbon components from the original equipment are merged and fed into newly-built depentanizing tower together, the crude gasoline containing no five carbon components is separated from the tower bottom, the carbon, four carbon and five carbon components extracted from the tower top are used as circulating material flow and returned to the reactor, and the small part is used as purge gas to maintain material balance.

The present invention will be further illustrated by the following examples, but is not limited to these examples.

Detailed Description

[ COMPARATIVE EXAMPLE 1 ]

A certain methanol-to-olefins plant provides 10 tons/hour of a carbon four-carbon five-olefin feedstock to an olefin cracking unit, wherein the total mass content of the C-pentaolefin is 95 percent, and the rest is C-pentaalkane. The olefin cracking device comprises a cracking reactor, a cracking gas compressor, a depropanizing tower and a depentanizing tower. After the raw material is treated by an olefin cracking device, 5.67 tons of crude propylene products per hour are obtained from the top of a depropanizing tower, wherein the mass fraction of diene (namely ethylene and propylene) is 88 percent, the carbon four obtained as a byproduct from the top of a depentanizing tower is 1.17 tons per hour, and the carbon five obtained as a byproduct from the bottom of the depentanizing tower is 3.15 tons per hour. The yield of the low-carbon olefin of the whole device based on the carbon four-carbon five-olefin in the raw material is 52 percent.

[ COMPARATIVE EXAMPLE 2 ]

An MTBE plant provides a 10 ton/hr post-ether tetraolefin feed to an olefin cracking plant, wherein the total mass content of the tetraolefins is 80% and the remainder is tetraolefins. After the raw material is treated by an olefin cracking device, a crude propylene product of 5.47 tons/hour is obtained, wherein the mass fraction of diene (namely ethylene and propylene) is 87 percent, the byproduct carbon four is 1.73 tons/hour, and the byproduct crude gasoline (containing five carbon components) is 2.81 tons/hour. The yield of the low-carbon olefin of the whole device based on the carbon four-carbon five-olefin in the raw material is 53 percent.

[ COMPARATIVE EXAMPLE 3 ]

A FCC unit provides 10 tons/hr of a four-carbon five-olefin feedstock to an olefin cracking unit, wherein the total mass content of four-carbon olefins is 65%, and the balance is four-carbon olefins. After the raw material is treated by an olefin cracking device, a crude propylene product of 4.33 tons/hour is obtained, wherein the mass fraction of diene (namely ethylene and propylene) is 86 percent, the byproduct carbon four is 3.56 tons/hour, and the byproduct crude gasoline (containing five carbon components) is 2.11 tons/hour. The yield of the low-carbon olefin of the whole device based on the medium-carbon four-carbon five-olefin in the raw material is 57 percent.

[ COMPARATIVE EXAMPLE 4 ]

A methanol to olefins plant is designed to provide 10 tons/hr of carbon four carbon five olefin feedstock to an olefin cracking unit, wherein the total mass content of the C-pentaolefin is 95 percent, and the rest is C-pentaalkane. Due to the change of the operation condition of the upstream methanol-to-olefins plant, the amount of the carbon four-carbon five-olefin raw material provided for the olefin cracking device is increased to 12 tons/hour, which exceeds the designed raw material processing capacity of the olefin cracking device, and the olefin cracking device cannot operate under the better process condition. After the raw material is treated by an olefin cracking device, 5.13 tons/hour of crude propylene products are produced, wherein the mass fraction of diene (namely ethylene and propylene) is 89.5 percent, the carbon four by-product obtained at the top of a depentanizer is 3.89 tons/hour, and the carbon five by-product obtained at the kettle of the depentanizer is 2.98 tons/hour. The yield of the low-carbon olefin of the whole device based on the medium-carbon four-carbon five-olefin in the raw material is 40.3 percent.

[ COMPARATIVE EXAMPLE 5 ]

A methanol to olefins plant is designed to provide 10 tons/hr of carbon four carbon five olefin feedstock to an olefin cracking unit, wherein the total mass content of the C-pentaolefin is 95 percent, and the rest is C-pentaalkane. Due to the change of the operation condition of the upstream methanol-to-olefins plant, the amount of the carbon four-carbon five-olefin raw material provided for the olefin cracking device is increased to 12 tons/hour, which exceeds the designed raw material processing capacity of the olefin cracking device, and the olefin cracking device cannot operate under the better process condition. If a small-scale olefin cracking unit is built to handle the increased 2 tons/hr of C-tetrapentacene feedstock in order to increase the overall olefin yield. According to the low-carbon olefin yield of 52 percent in the comparative example 1, the two sets of olefin cracking devices produce 6.8 tons/hour of crude propylene product, the obtained byproduct carbon four is 1.4 tons/hour, and the obtained byproduct crude gasoline (containing five carbon components) in the depentanizer kettle is 3.78 tons/hour.

[ example 1 ]

The olefin cracking device of the invention is newly built by taking the byproduct carbon four and the byproduct naphtha of the olefin cracking device in the comparative example 1 as raw materials, the catalyst which is the same as that of the original olefin cracking device is adopted, and the process flow is the same as that in the description of the attached drawings. Wherein the recycle ratio (i.e. the mass flow ratio of the carbon four-carbon five recycle stream 13 to the by-product carbon four-stream 3) is 2.3, the proportion of the carbon four-carbon five stream as the recycle stream is 74.5%, the outlet pressure of the compressor is 1.8MPa, the operating pressure of the depropanizer is 1.7MPa, and the operating pressure of the depentanizer is 0.5MPa. The newly-built olefin cracking device has the newly-increased crude propylene yield of 1.96 tons/hour, the yield is increased by 35 percent relative to the comparative example, and the diene concentration in the crude propylene is 86 percent. The total yield of the low-carbon olefin in the original device and the newly-built device is 70 percent, which is improved by 18 percent compared with the comparative example.

[ example 2 ]

The olefin cracking device of the invention is newly built by taking the byproduct carbon four and the byproduct naphtha of the olefin cracking device in the comparative example 1 as raw materials, a catalyst with cracking capability to the carbon four-carbon pentaalkane is adopted, and the process flow is the same as that in the description of the attached drawings. Wherein the recycle ratio is 2, the proportion of the carbon four-carbon five-material flow as the recycle flow is 86.5 percent, the outlet pressure of a compressor is 1.75MPa, the operating pressure of a depropanizing tower is 1.7MPa, and the operating pressure of a depentanizing tower is 0.6MPa. The newly-built olefin cracking device has the newly-increased crude propylene yield of 2.72 tons/hour, the yield is increased by 48 percent relative to the comparative example, and the diene concentration in the crude propylene is 90 percent. The total yield of the low-carbon olefin in the original device and the newly-built device is 78 percent, which is improved by 26 percent compared with the comparative example.

[ example 3 ]

The olefin cracking device of the invention is newly built by taking the byproduct carbon four and the byproduct naphtha of the olefin cracking device in the comparative example 2 as raw materials, a catalyst with cracking capability to the carbon four-carbon pentaalkane is adopted, and the process flow is the same as that in the description of the attached drawings. Wherein the recycle ratio is 3, the proportion of the carbon four-carbon five-material flow as the recycle flow is 94.2 percent, the outlet pressure of a compressor is 1.5MPa, the operating pressure of a depropanizing tower is 1.4MPa, and the operating pressure of a depentanizing tower is 0.35MPa. The newly-built olefin cracking device has the newly-increased crude propylene yield of 2.81 tons/hour, the yield is increased by 51 percent relative to the comparative example, and the diene concentration in the crude propylene is 89 percent. The total yield of the low-carbon olefin in the original device and the newly-built device is 91 percent, which is improved by 38 percent compared with the comparative example.

[ example 4 ] A method for producing a polycarbonate

The olefin cracking device of the invention is newly built by taking the byproduct carbon four and the byproduct naphtha of the olefin cracking device in the comparative example 2 as raw materials, a catalyst with cracking capability to the carbon four-carbon pentaalkane is adopted, and the process flow is the same as that in the description of the attached drawings. Wherein the recycle ratio is 4, the proportion of the carbon four-carbon five-material flow as the recycle flow is 95.6 percent, the outlet pressure of a compressor is 1MPa, the operating pressure of a depropanizing tower is 0.9MPa, and the operating pressure of a depentanizing tower is 0.4MPa. The newly-built olefin cracking device has the newly-added crude propylene yield of 3.0 tons/hour, the yield is increased by 55 percent relative to the comparative example, and the diene concentration in the crude propylene is 90 percent. The total yield of the low-carbon olefin in the original device and the newly-built device is 93 percent, which is improved by 40 percent compared with the comparative example.

[ example 5 ]

The olefin cracking device of the invention is newly built by taking the byproduct carbon four and the byproduct naphtha of the olefin cracking device in the comparative example 3 as raw materials, a catalyst with cracking capability to the carbon four-carbon pentaalkane is adopted, and the process flow is the same as that in the description of the attached drawings. Wherein the recycle ratio is 5, the proportion of the carbon four-carbon five-material flow as the recycle flow is 98.2 percent, the outlet pressure of a compressor is 1.5MPa, the operating pressure of a depropanizing tower is 1.4MPa, and the operating pressure of a depentanizing tower is 0.7MPa. The newly-built olefin cracking device has the newly-increased crude propylene yield of 3.7 tons/hour, the yield is increased by 85 percent relative to the comparative example, and the diene concentration in the crude propylene is 85 percent. The total yield of the low-carbon olefin in the original device and the newly-built device is 106 percent, which is improved by 49 percent compared with the comparative example. The reason for the overall lower olefin yield of greater than 100% is that the new plant uses a catalyst having cracking capability for the paraffins, whereas in the present invention the lower olefin yield is based on the carbon tetracarbon pentaolefins in the feedstock.

[ example 6 ]

The olefin cracking apparatus of the present invention was newly constructed by using 3.89 t/hr of by-produced C4 and 2.98 t/hr of by-produced naphtha as raw materials in the olefin cracking apparatus of comparative example 4, and a catalyst having a cracking ability for C four-carbon pentaalkane was used, and the process flow was the same as in the description of the drawings. Wherein, the circulation ratio is 5, the outlet pressure of the compressor is 1.5MPa, the operation pressure of the depropanizing tower is 1.4MPa, and the operation pressure of the depentanizing tower is 0.7MPa. Compared with the newly built small-scale olefin cracking device in comparative example 5, which is used for processing the carbon four-carbon five-olefin raw material with 2 tons/hour increased upstream, the yield of the crude propylene in the embodiment is increased by 47%.

[ example 7 ]

A certain methanol-to-olefins plant provides a raw olefin cracking unit with 10 tons/hour of carbon four-carbon five-olefin raw material, wherein the total mass content of the C-pentaolefin is 60 percent, and the rest is C-pentaalkane. The crude olefin cracking device comprises a cracking reactor, a cracking gas compressor, a depropanizing tower and a depentanizing tower. After the raw material is treated by an original olefin cracking device, 3.93 tons/hour of crude propylene products are obtained from the top of a depropanizing tower, wherein the mass fraction of diene (namely ethylene and propylene) is 86 percent, the carbon four by-product obtained from the top of a depentanizing tower is 4.86 tons/hour, and the carbon five by-product obtained from the bottom of the depentanizing tower is 1.21 tons/hour. The olefin cracking device is newly built by taking the byproduct carbon four and the byproduct naphtha of the original olefin cracking device as raw materials, a catalyst with cracking capability on the carbon four-carbon pentaalkane is adopted, and the process flow is the same as that in the description of the attached drawings. Wherein the circulation ratio is 2, the outlet pressure of the compressor is 2.0MPa, the operating pressure of the depropanizer is 1.8MPa, and the operating pressure of the depentanizer is 0.8MPa. The newly-built olefin cracking unit has the newly-increased crude propylene yield of 2.45 tons/hour.

[ example 8 ]

A certain methanol-to-olefins plant provides a raw olefin cracking unit with 10 tons/hour of carbon four-carbon five-olefin raw material, wherein the total mass content of the C-pentaolefin is 70 percent, and the rest is C-pentaalkane. The crude olefin cracking device comprises a cracking reactor, a cracking gas compressor, a depropanizing tower and a depentanizing tower. After the raw material is treated by an original olefin cracking device, 4.58 tons of crude propylene products per hour are obtained from the top of a depropanizing tower, wherein the mass fraction of diene (namely ethylene and propylene) is 87 percent, the carbon four obtained as a byproduct from the top of a depentanizing tower is 4.0 tons per hour, and the crude gasoline (containing five carbon components) obtained from the bottom of the depentanizing tower is 1.41 tons per hour. The olefin cracking device is newly built by taking the byproduct carbon four and the byproduct naphtha of the original olefin cracking device as raw materials, a catalyst with cracking capability on the carbon four-carbon pentaalkane is adopted, and the process flow is the same as that in the description of the attached drawings. Wherein the circulation ratio is 4, the outlet pressure of the compressor is 1.9MPa, the operating pressure of the depropanizer is 1.8MPa, and the operating pressure of the depentanizer is 0.7MPa. The newly-built olefin cracking device has the newly-added crude propylene yield of 3.2 tons/hour.

[ example 9 ]

A certain methanol-to-olefins plant provides a raw olefin cracking unit with 10 tons/hour of carbon four-carbon five-olefin raw material, wherein the total mass content of the C-pentaolefin is 75 percent, and the rest is C-pentaalkane. The crude olefin cracking device comprises a cracking reactor, a cracking gas compressor, a depropanizing tower and a depentanizing tower. After the raw material is treated by an original olefin cracking device, 4.91 tons of crude propylene products per hour are obtained from the top of a depropanizing tower, wherein the mass fraction of diene (namely ethylene and propylene) is 85 percent, the carbon four obtained as a byproduct from the top of a depentanizing tower is 3.58 tons per hour, and the crude gasoline (containing five carbon components) obtained from the bottom of the depentanizing tower is 1.51 tons per hour. The olefin cracking device is newly built by taking the byproduct carbon four and the byproduct naphtha of the original olefin cracking device as raw materials, a catalyst with cracking capability on the carbon four-carbon pentaalkane is adopted, and the process flow is the same as that in the description of the attached drawings. Wherein the circulation ratio is 2.5, the outlet pressure of the compressor is 1.8MPa, the operating pressure of the depropanizer is 1.7MPa, and the operating pressure of the depentanizer is 0.6MPa. The newly-built olefin cracking unit has the newly-increased crude propylene yield of 2.89 tons/hour.

[ example 10 ]

A certain methanol-to-olefins plant provides a raw olefin cracking unit with 10 tons/hour of carbon four-carbon five-olefin raw material, wherein the total mass content of the C-pentaolefin is 90 percent, and the rest is C-pentaalkane. The crude olefin cracking device comprises a cracking reactor, a cracking gas compressor, a depropanizing tower and a depentanizing tower. After the raw material is treated by an original olefin cracking device, 5.89 tons of crude propylene products per hour are obtained from the top of a depropanizing tower, wherein the mass fraction of diene (namely ethylene and propylene) is 88 percent, the carbon four obtained as a byproduct from the top of a depentanizing tower is 2.29 tons per hour, and the crude gasoline (containing five carbon components) obtained from the bottom of the depentanizing tower is 1.81 tons per hour. The olefin cracking device is newly built by taking the byproduct carbon four and the byproduct naphtha of the original olefin cracking device as raw materials, a catalyst with cracking capability on the carbon four-carbon pentaalkane is adopted, and the process flow is the same as that in the description of the attached drawings. Wherein the circulation ratio is 1.5, the outlet pressure of the compressor is 1.7MPa, the operating pressure of the depropanizer is 1.8MPa, and the operating pressure of the depentanizer is 0.5MPa. The newly-built olefin cracking unit has the newly-increased crude propylene yield of 1.85 tons/hour.

Claims

1. An energy expanding method for an olefin cracking device comprises the following steps: feeding the byproduct carbon four of the original olefin cracking device into a newly-built olefin cracking reactor, feeding the obtained reaction product into a newly-built depropanizing tower for separation, extracting a crude propylene product with increased yield from the top of the newly-built depropanizing tower, converging the kettle liquid of the newly-built depropanizing tower and the byproduct carbon-containing five-component gasoline of the original olefin cracking device, feeding the converged gasoline into the newly-built depentanizing tower, extracting crude gasoline from the kettle of the newly-built depentanizing tower, obtaining a carbon four-carbon by-product five-stream from the top of the newly-built depentanizing tower, and converging at least part of the carbon four-carbon by-product stream as a circulating material with the byproduct carbon four of the original olefin cracking device;

the circulation ratio of the newly-built olefin cracking reactor is 2.0-5.0; the newly-built olefin cracking reactor adopts a catalyst with cracking capability on C-V alkane.

2. The method for expanding energy of an olefin cracking unit as recited in claim 1, wherein the raw material of the raw olefin cracking unit is a hydrocarbon stream containing carbon four carbon five, wherein the total mass content of the carbon four carbon five olefins is 60-95 WT% relative to the total weight of the raw material.

3. The method for expanding the energy of the olefin cracking unit as recited in claim 2, wherein the raw material of the crude olefin cracking unit is a hydrocarbon stream containing carbon, four carbon and five carbon, which is a byproduct of the methanol to olefin unit.

4. The method of claim 1, wherein the newly constructed olefin cracking reactor is designed to handle no more than the original olefin cracking reactor.

5. The olefin cracking plant capacity expansion process of claim 1, wherein the proportion of the C four-C five stream as the recycle stream is at least 70%.

6. The olefin cracking plant capacity expansion process of claim 5, wherein the proportion of the C four-C five stream as the recycle stream is at least 90%.

7. The method of claim 1, wherein the new olefin cracking reactor is pressurized to 1.0-2.0 MPA and then fed into the new depropanizer.

8. The method of claim 1, wherein the newly-built depropanizer is operated at a pressure of 0.8 to 1.8MPA.

9. The method of claim 1, wherein the newly created depentanizer is operated at a pressure of 0.3 to 0.8MPA.