System and method for integrated preparation of polymerization grade olefins by dcc of carbon four comprehensive utilization

Abstract

The application belongs to the field of olefin production and discloses a system and method for preparing polymerization-grade olefin by DCC integration of comprehensive utilization of carbon four. The system comprises a DCC cracking unit, a fractionation unit, a compression and impurity removal unit, a cryogenic separation unit, a steam cracking unit, an alkylation reaction unit and an OCC cracking unit; a first outlet of the cryogenic separation unit and a refinery liquefied gas feed pipeline are connected with an inlet of the alkylation reaction unit respectively; a first outlet of the alkylation reaction unit is connected with an inlet of the OCC cracking unit and an inlet of the compression and impurity removal unit in sequence; a second outlet of the cryogenic separation unit, a second outlet of the alkylation reaction unit and a refinery propane feed pipeline are connected with an inlet of the steam cracking unit respectively, and an outlet of the steam cracking unit is connected with an inlet of the fractionation unit; and the inlet of the compression and impurity removal unit is further connected with a mixed dry gas feed pipeline. The application maximizes the preparation of olefin from raw materials.

Description

Technical Field

[0001] This invention belongs to the field of olefin production, specifically relating to a system and method for the integrated preparation of polymer-grade olefins using C4-based DCC. Background Technology

[0002] In the traditional DCC (Deep Catalytic Cracking) separation process, the feedstock heavy oil is catalytically cracked to obtain reaction oil and gas. This reaction oil and gas is then fractionated and stabilized through absorption, removing heavy components such as coke, oil slurry, diesel, and gasoline to obtain light gas and liquid phases. These are then subjected to dual desulfurization to obtain desulfurized LPG and desulfurized dry gas (removing inorganic sulfur from dry gas and LPG, and organic sulfur from LPG and gasoline). The desulfurized LPG is then separated to obtain LPG mainly composed of propylene, propane, and mixed C4. The propylene gas requires further refining to obtain polymer-grade propylene, while the propane undergoes further steam cracking to produce olefins. The desulfurized dry gas undergoes dry gas enrichment and impurity removal treatment (oil absorption or PSA) to remove methane / hydrogen tail gas, yielding enriched mixed C2 dry gas. This enriched mixed C2 dry gas undergoes cryogenic separation to obtain polymer-grade ethylene. The saturated alkanes, refinery propane, and propane from the cryogenic separation are then processed through a light hydrocarbon steam cracking process to produce polymer-grade olefins. (See...) Figure 1 .

[0003] On the other hand, small amounts of mixed dry gas from other sources (refinery FCC dry gas, coking dry gas, etc.) need to be utilized as resources. Therefore, further dry gas pretreatment (i.e., the aforementioned dry gas enrichment and impurity removal treatment) is required, followed by cryogenic separation to recover ethylene, propylene, ethane, and propane, and to obtain byproducts crude hydrogen and methane tail gas. See [link to relevant documentation]. Figure 1 .

[0004] The products of the above process include polymer-grade ethylene and polymer-grade propylene, while byproducts include heavy oil, stabilized gasoline, liquefied petroleum gas (LPG), crude hydrogen, methane tail gas, mixed C4, and crude cracked gasoline. The mixed C4 does not undergo further ethylene / propylene production, resulting in low resource utilization efficiency. After alkylation to utilize isobutane, the resulting n-butane can be sent for steam cracking to increase olefin production. The remaining C4 olefins can be processed through OCC (Olefin Catalytic Cracking) to increase propylene and a small amount of ethylene, but this requires compression, cold separation, and hot separation units to obtain polymer-grade ethylene and propylene. OCC is much smaller in scale than DCC, and the redundant separation equipment leads to unreasonable resource utilization, low investment efficiency, and management difficulties.

[0005] The above describes existing DCC (Deep Catalytic Cracking) reaction gas processing solutions. Their characteristics include the need for simultaneous DCC and steam cracking units to obtain polymer-grade ethylene and propylene. Furthermore, the dry gas recovery unit employs different process routes (oil absorption or PSA), resulting in a C2 loss rate of 8-17%. This leads to low overall polymer-grade olefin recovery and the lack of further resource utilization for the mixed C4 byproduct in propylene production. Therefore, the existing solutions suffer from long processes, low polymer-grade olefin recovery, redundant separation units or equipment, and high investment costs.

[0006] Therefore, there is an urgent need to propose a system and method for the integrated preparation of polymer-grade olefins using C4-based DCC. Summary of the Invention

[0007] The purpose of this invention is to address the shortcomings of existing technologies by proposing a system and method for the integrated production of polymer-grade olefins using DCC (Deep Catalytic Cracking), a C4 hydrocarbon vapor cracking process, and OCC (Olefin Catalytic Cracking). The system and method of this invention utilize DCC, light hydrocarbon steam cracking, and OCC as the "three ends" of feedstock cracking, sharing a single unit for fractionation, compression purification, and cryogenic separation, forming a "one end," which maximizes the production of olefins from the feedstock.

[0008] To achieve the above objectives, the present invention provides a system for the integrated preparation of polymer-grade olefins using C4-based DCC, which includes a DCC cracking unit, a fractionation unit, a compression and impurity removal unit, a cryogenic separation unit, a vapor cracking unit, an alkylation reaction unit, and an OCC cracking unit.

[0009] The DCC pyrolysis unit, fractionation unit, compression and impurity removal unit, and cryogenic separation unit are connected in sequence.

[0010] The first outlet of the cryogenic separation unit and the refinery liquefied gas feed line are respectively connected to the inlet of the alkylation reaction unit;

[0011] The first outlet of the alkylation reaction unit is connected in sequence to the inlet of the OCC cracking unit and the compression and impurity removal unit;

[0012] The second outlet of the cryogenic separation unit, the second outlet of the alkylation reaction unit, and the refinery propane feed line are respectively connected to the inlet of the steam cracking unit, and the outlet of the steam cracking unit is connected to the inlet of the fractionation unit.

[0013] The inlet of the compression and impurity removal unit is also connected to a mixed dry gas feed pipeline.

[0014] Another aspect of the present invention provides a method for the integrated preparation of polymer-grade olefins using C4-based DCC, wherein the method is carried out in the system described above and includes the following steps:

[0015] S1: The reaction oil and gas produced by the DCC cracking unit and the cracked gas from the steam cracking unit are fed into the fractionation unit for fractionation to obtain rich gas; the rich gas, crude propylene from the OCC unit and mixed dry gas are fed into the compression and impurity removal unit for compression and impurity removal to obtain impurity-removed process gas.

[0016] S2: The purified process gas is sent to the cryogenic separation unit for cryogenic step-by-step separation to obtain polymer-grade ethylene, polymer-grade propylene product, hydrogen-rich gas, methane tail gas, mixed C4, saturated alkanes and crude cracked gasoline.

[0017] S3: The mixed C4 and refinery liquefied gas are fed into the alkylation reaction unit for alkylation treatment to obtain alkylated oil, n-butane and residual C4; the n-butane, the saturated alkane and refinery propane are fed into the steam cracking unit for cracking treatment to obtain the cracked gas, which is then fed into the fractionation unit.

[0018] S4: The remaining C4 is fed into the OCC cracking unit for processing to obtain crude propylene and crude butane; the crude propylene is fed into the compression and impurity removal unit.

[0019] The technical solution of the present invention has the following beneficial effects:

[0020] (1) The system and method of the present invention use DCC (deep catalytic cracking), light hydrocarbon steam cracking and OCC (olefin catalytic cracking) as the "three heads" of feedstock cracking, and share a set of fractionation, compression and impurity removal and cryogenic separation units to form "one tail". It can maximize the production of olefins from feedstock to achieve the requirement of "fully utilizing" the feedstock, and can simultaneously obtain polymer-grade ethylene and polymer-grade propylene products, as well as by-products such as hydrogen-rich gas, methane tail gas and crude cracked gasoline.

[0021] (2) The system and method of the present invention optimize the impurity removal and separation process, avoiding the loss of C2 components during dry gas recovery. The saturated alkanes (ethane / propane) separated by the cryogenic separation unit are recycled as raw materials to the steam cracking unit to increase olefin production; the remaining C4 obtained after alkylation of the mixed C4 separated by the cryogenic separation unit is converted into crude propylene gas by OCC (olefin catalytic cracking), and mixed with mixed dry gas (dry gas from refinery FCC, coking dry gas, etc.) and fed into the compression impurity removal unit. After compression impurity removal and cryogenic separation, the separation efficiency (i.e., polymerization-grade olefin recovery rate and diene yield) is improved, forming a DCC integrated reaction gas recovery technology with "three heads and one tail" comprehensive utilization of C4, which greatly simplifies the DCC (deep catalytic cracking) reaction oil and gas to ethylene production process, and at the same time increases the polymerization-grade ethylene recovery rate from 83-92% to over 99.6%.

[0022] (3) This invention simplifies the process by proposing a "one-tail" separation process, which eliminates the need for a set of equipment such as quenching / fractionation, absorption stabilization, gas separation, and dry gas recovery units. Two desulfurization lines are simplified into one desulfurization line, thus forming a "one-tail" process of fractionation, compression, and separation. This reduces the number of equipment units, thereby reducing investment and land occupation, as well as reducing the complexity of equipment operation and improving the operational stability of the equipment.

[0023] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0024] The above and other objects, features and advantages of the present invention will become more apparent from the more detailed description of exemplary embodiments of the invention in conjunction with the accompanying drawings.

[0025] Figure 1 A process flow diagram for the production of polymer-grade olefins from DCC reaction oil and gas is shown in the prior art.

[0026] Figure 2 The diagram shows a process flow chart for the integrated preparation of polymer-grade olefins using C4-based DCC, as provided in Embodiment 1 of the present invention. Detailed Implementation

[0027] Preferred embodiments of the invention will now be described in more detail. While preferred embodiments of the invention are described below, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the invention will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0028] The present invention provides a system for the integrated preparation of polymer-grade olefins using C4-based DCC, which includes a DCC cracking unit, a fractionation unit, a compression and impurity removal unit, a cryogenic separation unit, a vapor cracking unit, an alkylation reaction unit, and an OCC cracking unit.

[0029] The DCC pyrolysis unit, fractionation unit, compression and impurity removal unit, and cryogenic separation unit are connected in sequence.

[0030] The first outlet of the cryogenic separation unit and the refinery liquefied gas feed line are respectively connected to the inlet of the alkylation reaction unit;

[0031] The first outlet of the alkylation reaction unit is connected in sequence to the inlet of the OCC cracking unit and the compression and impurity removal unit;

[0032] The second outlet of the cryogenic separation unit, the second outlet of the alkylation reaction unit, and the refinery propane feed line are respectively connected to the inlet of the steam cracking unit, and the outlet of the steam cracking unit is connected to the inlet of the fractionation unit.

[0033] The inlet of the compression and impurity removal unit is also connected to a mixed dry gas feed pipeline.

[0034] According to the present invention, preferably,

[0035] The first outlet of the cryogenic separation unit is connected to the inlet of the alkylation reaction unit via a mixed C4 output pipeline;

[0036] The first outlet of the alkylation reaction unit is connected in sequence to the inlet of the OCC cracking unit and the compression and impurity removal unit via the remaining C4 output pipeline;

[0037] The second outlet of the cryogenic separation unit is connected to the inlet of the vapor cracking unit via a saturated alkane circulation pipeline, and the second outlet of the alkylation reaction unit is connected to the inlet of the vapor cracking unit via a n-butane output pipeline.

[0038] According to the present invention, preferably, the cryogenic separation unit further includes at least one of a cold box, a demethanizer, a deethaner, an ethylene distillation column, a depropanizer, a propylene distillation column, a debutanizer, an ethylene generator, and a propylene generator; the cryogenic separation unit is also connected to a hydrogen-rich gas output pipeline, a methane tail gas output pipeline, a polymer-grade ethylene output pipeline, a polymer-grade propylene output pipeline, and a crude cracked gasoline output pipeline.

[0039] According to the present invention, preferably, the third outlet of the alkylation reaction unit is connected to an alkylation oil output pipeline.

[0040] According to the present invention, preferably, the OCC cracking unit is also connected to a crude butane output pipeline.

[0041] According to the present invention, preferably, the fractionation unit is also connected to a heavy component output pipeline.

[0042] According to the present invention, preferably, the compression and impurity removal unit includes at least one of a compressor, an amine washing / alkali washing tower, and a de-impurity adsorption bed.

[0043] According to the present invention, preferably, a selective hydrogenation device is provided between the cryogenic separation unit and the alkylation reaction unit. In the present invention, if the content of dienes and alkynes in the mixed C4 hydrocarbons is high, a C4 selective hydrogenation device should be provided to meet the feed requirements for alkylation.

[0044] Another aspect of the present invention provides a method for the integrated preparation of polymer-grade olefins using C4-based DCC, wherein the method is carried out in the system described above and includes the following steps:

[0045] S1: The reaction oil and gas produced by the DCC cracking unit and the cracked gas from the steam cracking unit are fed into the fractionation unit for fractionation to obtain rich gas; the rich gas, crude propylene from the OCC unit and mixed dry gas are fed into the compression and impurity removal unit for compression and impurity removal to obtain impurity-removed process gas.

[0046] S2: The purified process gas is sent to the cryogenic separation unit for cryogenic step-by-step separation to obtain polymer-grade ethylene, polymer-grade propylene product, hydrogen-rich gas, methane tail gas, mixed C4, saturated alkanes and crude cracked gasoline.

[0047] S3: The mixed C4 and refinery liquefied gas are fed into the alkylation reaction unit for alkylation treatment to obtain alkylated oil, n-butane and remaining C4; the n-butane, the saturated alkanes and refinery propane are fed into the steam cracking unit for cracking treatment to obtain the cracked gas, which is then fed into the fractionation unit; the alkylated oil is directly used as gasoline product.

[0048] S4: The remaining C4 is fed into the OCC cracking unit for processing to obtain crude propylene and crude butane; the crude propylene is fed into the compression and impurity removal unit.

[0049] According to the present invention, preferably, the feedstock in the DCC pyrolysis unit is hydrogenated wax oil and / or hydrogenated heavy oil.

[0050] According to the present invention, preferably, the gas in the fractionation unit is treated by fractionation and the removed substances are heavy components with a distillation range ≥150℃. Preferably, the substances removed by the fractionation unit include coke, oil slurry, diesel oil and cracked gasoline.

[0051] According to the present invention, preferably, the impurities removed from the gas in the compression and impurity removal unit after the compression and impurity removal process include CO2, H2S, and NO.x Organic sulfur, arsenic and mercury.

[0052] According to the present invention, preferably, the impurity content in the gas after being processed by the compression and impurity removal unit is ≤1ppm.

[0053] According to the present invention, preferably, the outlet pressure of the compressor in the compression and impurity removal unit is 3 to 4 MPaG.

[0054] According to the present invention, preferably, the mixed dry gas is refinery FCC dry gas and / or coking dry gas.

[0055] According to the present invention, preferably, the cooling capacity of the cryogenic separation unit is provided by a superimposed refrigeration system of an ethylene generator and a propylene generator.

[0056] According to the present invention, preferably, the methane hydrogen tail gas in the cryogenic separation unit is separated at a temperature of -160 to -165°C to obtain the hydrogen-rich gas and a portion of the methane tail gas.

[0057] According to the present invention, preferably, the purity of H2 / N2 in the hydrogen-rich gas is 94-96 mol%.

[0058] According to the present invention, preferably, the remaining methane tail gas in the methane tail gas comes from the top gas phase of the demethanizer.

[0059] In the cryogenic separation unit of the present invention, as a preferred embodiment, the methane-hydrogen tail gas is separated into methane tail gas and hydrogen-rich gas at -163°C, thereby obtaining hydrogen-rich gas with higher added value, i.e., H2 / N2 of 95 mol%. Compared with the existing process, hydrogen can be recovered to the maximum extent without pressure swing adsorption (PSA), reducing the large amount of hydrogen lost by the dry gas recovery unit with the methane-hydrogen tail gas.

[0060] According to the present invention, preferably, the recovery rate of polymer-grade olefins is 99.6% or higher; the diene yield is increased by 45%-55%.

[0061] In this invention, DCC (Deep Catalytic Cracking), light hydrocarbon steam cracking (i.e., steam cracking unit), and OCC (Olefin Catalytic Cracking) are used as the "three heads" of feedstock cracking. The oil and gas produced by DCC cracking and the cracked gas produced by light hydrocarbon steam cracking are fractionated to remove heavy components such as coke, oil slurry, diesel, and cracked gasoline to obtain rich gas. The rich gas, crude propylene gas from OCC (Olefin Catalytic Cracking), and mixed dry gas are compressed and impurity removed, and cryogenically separated by compression and impurity removal units and cryogenic separation units to separate polymer-grade ethylene and polymer-grade propylene products, forming the "one tail". The composition and molecular weight of the crude propylene gas from OCC (Olefin Catalytic Cracking) and mixed dry gas (refinery FCC dry gas, coking dry gas, etc.) are similar to those of the rich gas. At the same time, the gas phase volume is relatively small compared to DCC, so they can be incorporated into the compression unit and mixed with the rich gas. This does not have a significant impact on the subsequent separation system process and equipment settings. Furthermore, after impurity removal and olefin recovery treatment, the comprehensive utilization efficiency of resources and olefin recovery rate can be improved.

[0062] In this invention, since the feedstock for DCC (deep catalytic cracking) is heavy oil such as hydrogenated wax oil and / or hydrogenated heavy oil, the saturated alkanes (ethane / propane) contained in the reaction gas obtained from cracking cannot be used as feedstock for catalytic cracking after final separation. They need to be further cracked in the steam cracking unit to produce olefins. This invention can maximize the conversion of saturated alkanes (ethane / propane) into olefins, so that the final product structure does not contain ethane / propane or other alkanes. In addition, the mixed C4 and refinery liquefied gas separated by the cryogenic separation unit are used as alkylation feedstocks. After alkylation, n-butane, residual C4 olefins, and alkylated oil are obtained. Among them, the alkylated oil is directly used as gasoline product; n-butane, along with refinery propane and saturated alkanes such as ethane / propane obtained from cryogenic separation, are recycled to the steam cracking unit for light hydrocarbon steam cracking to produce cracked gas, which is then incorporated into the oil and gas from DCC cracking; the residual C4 olefins are processed by OCC (olefin catalytic cracking) to produce crude propylene and crude butane as a byproduct. Crude propylene, mixed dry gas, and rich gas are mixed and then compressed for impurity removal. This invention greatly simplifies the process of recovering ethylene from the reaction gas of deep catalytic cracking (DCC), while increasing the diene yield by 45%-55% and the olefin recovery rate from 83-92% to over 99.6%. It also improves the overall utilization efficiency of crude propylene prepared from mixed C4 hydrocarbons, simplifies the process unit flow, and reduces investment costs, resulting in a final product structure that does not contain alkanes such as ethane, propane, or butane.

[0063] The system and method of this invention avoid the loss of C2 components in the dry gas recovery unit. In existing processes, to recover ethylene from dry gas, the methane hydrogen tail gas needs to be removed in the dry gas recovery unit to obtain a concentrated mixed C2 dry gas. This process usually uses oil absorption or PSA, both of which result in 8-17% of the C2 components being mixed into the methane tail gas and cannot be recovered. However, the cryogenic separation distillation operation of this invention allows for better control of the separation parameters of the distillation column at a lower operating temperature. While obtaining polymer-grade ethylene and polymer-grade propylene, it also improves their recovery rates and reduces the loss of saturated alkanes such as ethane / propane, thereby significantly improving the diene yield of the unit.

[0064] The system and method of this invention simplify the separation process and reduce equipment investment. In existing processes, two separation processes are required: one for separating DCC reaction oil and gas, which undergoes fractionation, absorption stabilization, and other oil absorption processes to obtain light gas and liquid phases, followed by dual desulfurization to remove organic and inorganic sulfur, yielding LPG and dry gas. LPG is then separated to obtain propylene, which sometimes requires further refining depending on the requirements of downstream units; the dry gas undergoes pretreatment such as dry gas recovery before entering cryogenic separation to obtain polymer-grade ethylene. Ethane / propane is recycled to the cracking furnace for cracking, and after rapid cooling and compression, it also enters cryogenic separation to fully extract the ethane / propane. However, using the "one-tail" separation process of this invention, the reaction oil and gas from DCC cracking and the cracked gas from light hydrocarbon steam cracking are sent together to the fractionation unit to remove heavy components such as diesel and cracked gasoline, yielding rich gas; the rich gas, crude propylene gas from OCC (olefin catalytic cracking), and mixed dry gas are then pressurized by a compressor to remove CO2, H2S, and NO. x Impurities such as organic sulfur, arsenic, and mercury are separated in stages in the cryogenic separation unit to obtain polymer-grade ethylene and polymer-grade propylene products. Saturated alkanes such as ethane / propane are directly recycled to the light hydrocarbon cracking furnace (steam cracking unit) in the "three heads" for cracking, which greatly simplifies the separation process. At the same time, the purity of the products does not require further refining and can be directly used as raw materials for downstream polyolefin units, EOEG and other units.

[0065] The present invention will be specifically illustrated below through examples.

[0066] Example 1

[0067] This embodiment provides a system for the integrated preparation of polymer-grade olefins using C4-based DCC, such as... Figure 2 As shown in the process flow diagram, the system includes a DCC cracking unit, a fractionation unit, a compression and impurity removal unit, a cryogenic separation unit, a steam cracking unit, an alkylation reaction unit, and an OCC cracking unit.

[0068] The DCC pyrolysis unit, fractionation unit, compression and impurity removal unit, and cryogenic separation unit are connected in sequence.

[0069] The first outlet of the cryogenic separation unit is connected to the inlet of the alkylation reaction unit via a mixed C4 output pipeline; the inlet of the alkylation reaction unit is also connected to a refinery liquefied gas feed pipeline.

[0070] The first outlet of the alkylation reaction unit is connected in sequence to the inlet of the OCC cracking unit and the compression and impurity removal unit via the remaining C4 output pipeline;

[0071] The second outlet of the cryogenic separation unit is connected to the inlet of the steam cracking unit via a saturated alkane circulation pipeline, and the second outlet of the alkylation reaction unit is connected to the inlet of the steam cracking unit via a n-butane output pipeline; the inlet of the steam cracking unit is also connected to a refinery propane feed pipeline.

[0072] The cryogenic separation unit also includes other outlets, an ethylene generator, and a propylene generator; the other outlets are respectively connected to a hydrogen-rich gas output pipeline, a methane tail gas output pipeline, a polymerization-grade ethylene output pipeline, a polymerization-grade propylene output pipeline, and a crude cracked gasoline output pipeline. The third outlet of the alkylation reaction unit is connected to the alkylation oil output pipeline;

[0073] The outlet of the steam cracking unit is connected to the inlet of the fractionation unit;

[0074] The inlet of the compression and impurity removal unit is also connected to a mixed dry gas feed pipeline. The compression and impurity removal unit includes a compressor and a de-impurity adsorption bed.

[0075] The OCC cracking unit is also connected to a crude butane output pipeline;

[0076] The fractionation unit is also connected to a heavy component output pipeline.

[0077] The method for the integrated DCC (C4-based) preparation of polymer-grade olefins in the above system includes the following steps:

[0078] S1: Hydrogenated heavy oil is used as the feedstock of the DCC cracking unit. The reaction oil and gas produced by the DCC cracking unit and the cracked gas from the steam cracking unit are fed into the fractionation unit for fractionation treatment to remove heavy components such as coke, oil slurry, diesel, and cracked gasoline, to obtain rich gas. The rich gas, crude propylene from the OCC unit, and mixed dry gas are fed into the compression and impurity removal unit for compression and impurity removal treatment to remove CO2, H2S, and NO. x Impurities such as organic sulfur, arsenic, and mercury are removed to obtain a purified process gas; the impurity content in the gas after being processed by the compression purification unit is ≤1ppm; the mixed dry gas is refinery FCC dry gas and coking dry gas.

[0079] S2: The purified process gas is fed into the cryogenic separation unit for cryogenic staged separation to obtain polymer-grade ethylene, polymer-grade propylene product, hydrogen-rich gas, methane tail gas, mixed C4, saturated alkanes, and crude cracked gasoline; wherein, the cooling capacity of the cryogenic separation unit is provided by cascade refrigeration of the ethylene generator and the propylene generator; the separation of methane tail gas and hydrogen-rich gas from the methane-hydrogen tail gas is carried out at -163°C to obtain hydrogen-rich gas with higher added value, i.e., H2 / N2 of 95 mol%, and a portion of the methane tail gas, with the remaining methane tail gas coming from the top gas phase of the demethanizer.

[0080] S3: The mixed C4 and refinery liquefied gas are fed into the alkylation reaction unit for alkylation treatment to obtain alkylated oil, n-butane and remaining C4; the n-butane, the saturated alkanes and refinery propane are fed into the steam cracking unit for cracking treatment to obtain the cracked gas, which is then fed into the fractionation unit; the alkylated oil is directly used as gasoline product.

[0081] S4: The remaining C4 is fed into the OCC cracking unit for processing to obtain crude propylene and crude butane; the crude propylene is fed into the compression and impurity removal unit.

[0082] The ethylene yield obtained by the system and method of this embodiment is increased from 3.6% to over 11%, the propylene yield is increased from 16% to 19%, that is, the diene yield is increased by 53%, and the recovery rate of polymer-grade olefins is over 99.6%.

[0083] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A system for the integrated preparation of polymer-grade olefins using C4-based DCC, characterized in that, The system includes a DCC cracking unit, a fractionation unit, a compression and impurity removal unit, a cryogenic separation unit, a steam cracking unit, an alkylation reaction unit, and an OCC cracking unit; The DCC pyrolysis unit, fractionation unit, compression and impurity removal unit, and cryogenic separation unit are connected in sequence. The first outlet of the cryogenic separation unit and the refinery liquefied gas feed line are respectively connected to the inlet of the alkylation reaction unit; The first outlet of the alkylation reaction unit is connected in sequence to the inlet of the OCC cracking unit and the compression and impurity removal unit; The second outlet of the cryogenic separation unit, the second outlet of the alkylation reaction unit, and the refinery propane feed line are respectively connected to the inlet of the steam cracking unit, and the outlet of the steam cracking unit is connected to the inlet of the fractionation unit. The inlet of the compression and impurity removal unit is also connected to a mixed dry gas feed pipeline; The cryogenic separation unit is also connected to a hydrogen-rich gas output pipeline, a methane tail gas output pipeline, a polymer-grade ethylene output pipeline, a polymer-grade propylene output pipeline, and a crude cracked gasoline output pipeline.

2. The system for integrated DCC preparation of polymer-grade olefins utilizing C4 as described in claim 1, wherein, The first outlet of the cryogenic separation unit is connected to the inlet of the alkylation reaction unit via a mixed C4 output pipeline; The first outlet of the alkylation reaction unit is connected in sequence to the inlet of the OCC cracking unit and the compression and impurity removal unit via the remaining C4 output pipeline; The second outlet of the cryogenic separation unit is connected to the inlet of the vapor cracking unit via a saturated alkane circulation pipeline, and the second outlet of the alkylation reaction unit is connected to the inlet of the vapor cracking unit via a n-butane output pipeline. The cryogenic separation unit further includes at least one of a cold box, a demethanizer, a deethaner, an ethylene distillation column, a depropanizer, a propylene distillation column, a debutanizer, an ethylene generator, and a propylene generator.

3. The system for integrated DCC preparation of polymer-grade olefins utilizing C4 as described in claim 1, wherein, The third outlet of the alkylation reaction unit is connected to the alkylation oil output pipeline; The OCC cracking unit is also connected to a crude butane output pipeline; The fractionation unit is also connected to a heavy component output pipeline.

4. The system for integrated DCC preparation of polymer-grade olefins utilizing C4 as described in claim 1, wherein, The compression and impurity removal unit includes at least one of a compressor, an amine washing / alkali washing tower, and a de-impurity adsorption bed.

5. The system for integrated DCC preparation of polymer-grade olefins utilizing C4 as described in any one of claims 1-4, wherein, A selective hydrogenation device is provided between the cryogenic separation unit and the alkylation reaction unit.

6. A method for the integrated preparation of polymer-grade olefins using C4-based DCC, characterized in that, The method is performed in the system described in any one of claims 1-5, and includes the following steps: S1: The reaction oil and gas produced by the DCC cracking unit and the cracked gas from the steam cracking unit are fed into the fractionation unit for fractionation to obtain rich gas; the rich gas, crude propylene from the OCC unit and mixed dry gas are fed into the compression and impurity removal unit for compression and impurity removal to obtain impurity-removed process gas. S2: The purified process gas is sent to the cryogenic separation unit for cryogenic step-by-step separation to obtain polymer-grade ethylene, polymer-grade propylene product, hydrogen-rich gas, methane tail gas, mixed C4, saturated alkanes and crude cracked gasoline. S3: The mixed C4 and refinery liquefied gas are fed into the alkylation reaction unit for alkylation treatment to obtain alkylated oil, n-butane and residual C4; the n-butane, the saturated alkane and refinery propane are fed into the steam cracking unit for cracking treatment to obtain the cracked gas, which is then fed into the fractionation unit. S4: The remaining C4 is fed into the OCC cracking unit for processing to obtain crude propylene and crude butane; the crude propylene is fed into the compression and impurity removal unit.

7. The method for integrated DCC preparation of polymer-grade olefins utilizing C4 as described in claim 6, wherein, The feedstock in the DCC pyrolysis unit is hydrogenated wax oil and / or hydrogenated heavy oil.

8. The method for integrated preparation of polymer-grade olefins using C4-based DCC according to claim 6, wherein, After the gas in the fractionation unit is fractionated, the removed substances are heavy components with a distillation range ≥150℃. After the gas in the compression and impurity removal unit undergoes the compression and impurity removal process, impurities including CO2, H2S, and NO are removed. x Organic sulfur, arsenic, and mercury; the impurity content in the gas after being processed by the compression and impurity removal unit is ≤1ppm; The outlet pressure of the compressor in the compression and impurity removal unit is 3~4 MPaG; The mixed dry gas is refinery FCC dry gas and / or coking dry gas.

9. The method for integrated preparation of polymer-grade olefins using C4-based DCC according to claim 8, wherein, The substances removed by the fractionation unit include coke, oil slurry, diesel fuel, and pyrolysis gasoline.

10. The method for integrated preparation of polymer-grade olefins using C4-based DCC according to claim 6, wherein, The cooling capacity of the cryogenic separation unit is provided by a cascade refrigeration system consisting of an ethylene generator and a propylene generator; The methane hydrogen tail gas in the cryogenic separation unit is separated at a temperature of -160 to -165°C to obtain the hydrogen-rich gas and a portion of the methane tail gas. The purity of H2 / N2 in the hydrogen-rich gas is 94-96 mol%; The remaining methane tail gas in the methane tail gas comes from the top gas phase of the demethanizer.

11. The method for integrated preparation of polymer-grade olefins using DCC with comprehensive utilization of C4 as described in any one of claims 6-10, wherein, The recovery rate of polymer-grade olefins is over 99.6%; the yield of dienes is increased by 45%-55%.

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