CN115710152A - System and method for preparing polymerization-grade olefin through DCC (DCC) integration with comprehensive utilization of carbon four - Google Patents
System and method for preparing polymerization-grade olefin through DCC (DCC) integration with comprehensive utilization of carbon four Download PDFInfo
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Abstract
The invention belongs to the field of olefin production, and discloses a system and a method for preparing polymerization-grade olefin by DCC (DCC) integrated preparation by comprehensively utilizing C4. The system comprises a DCC cracking unit, a fractionation unit, a compression 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 respectively connected with an inlet of the alkylation reaction unit; a first outlet of the alkylation reaction unit is sequentially connected with inlets of the OCC cracking unit and the compression impurity removal unit; a second outlet of the cryogenic separation unit, a second outlet of the alkylation reaction unit and a refinery propane feed pipeline are respectively connected with an inlet of the steam cracking unit, and an outlet of the steam cracking unit is connected with an inlet of the fractionation unit; and the inlet of the compression impurity removal unit is also connected with a mixed dry gas feeding pipeline. The invention prepares olefin from raw material to the maximum extent.
Description
Technical Field
The invention belongs to the field of olefin production, and particularly relates to a system and a method for preparing polymerization-grade olefin by DCC (DCC) integrated synthesis of carbon four.
Background
In the separation process flow of the traditional DCC (deep catalytic cracking), reaction oil gas is obtained after catalytic cracking of raw material heavy oil; fractionating the reaction oil gas, absorbing stably, removing heavy components such as coke, oil slurry, diesel oil, gasoline and the like to obtain light gas and liquid phases; the LPG and the dry gas are subjected to double-desorption to obtain desulfurized LPG and desulfurized dry gas (i.e. the dry gas and the liquefied gas are subjected to inorganic sulfur removal, and the liquefied gas and the gasoline are subjected to organic sulfur removal); the desulfurized liquefied gas is subjected to gas separation to obtain liquefied gas mainly containing propylene, propane and mixed carbon four, the propylene gas needs to be further refined to obtain a polymerization-grade propylene product, and the propane enters steam cracking for further cracking to prepare olefin; the desulfurized dry gas is subjected to dry gas concentration and impurity removal treatment (oil absorption or PSA) to remove methane/hydrogen tail gas, so as to obtain concentrated mixed carbon dioxide dry gas; the concentrated mixed carbon dioxide dry gas is subjected to cryogenic separation to obtain a polymer grade ethylene product, and the saturated alkane, refinery propane and propane obtained from gas separation subjected to cryogenic separation are subjected to a light hydrocarbon steam cracking process to prepare polymer grade olefin, as shown in figure 1.
On the other hand, since a small amount of mixed dry gas (refinery FCC dry gas, coke dry gas, etc.) from other places needs to be recycled, further dry gas pretreatment (i.e., the above-mentioned dry gas concentration and impurity removal treatment) is required, and further cryogenic separation is performed to recover ethylene, propylene, ethane, and propane, and by-products, crude hydrogen and methane tail gas are obtained, as shown in fig. 1.
The product of the process comprises polymerization-grade ethylene and polymerization-grade propylene, and the byproducts comprise heavy oil, stable gasoline, liquefied gas, crude hydrogen, methane tail gas, mixed C4 and crude pyrolysis gasoline. Wherein the mixed C4 is not used for further preparing the ethylene/propylene, and the comprehensive utilization efficiency of resources is lower. The isobutane is removed from the mixed carbon four through alkylation treatment, and the obtained normal butane can be sent to steam cracking to increase the yield of olefin; the yield of propylene and a small amount of ethylene can be increased by using the residual carbon tetraolefins through OCC (olefin catalytic cracking), but a compression unit, a cold separation unit and a hot separation unit are needed to obtain polymer-grade ethylene and polymer-grade propylene. The OCC scale is much smaller than that of the DCC, and the separation equipment is repeatedly arranged, so that the comprehensive utilization of the resources in the whole plant is unreasonable, the investment benefit is low, the management is difficult and the like.
The scheme is the prior DCC (deep catalytic cracking) reaction oil gas treatment scheme and is characterized in that: the DCC (deep catalytic cracking) device and the steam cracking device are required to be arranged at the same time to obtain polymerization-grade ethylene and polymerization-grade propylene products, meanwhile, the dry gas recovery processing unit has different process routes, namely oil absorption or PSA, the loss rate of the carbon two component is 8-17%, the recovery rate of the polymerization-grade olefin in the whole process is low, and the byproduct mixed carbon C is not further comprehensively utilized for preparing propylene. Therefore, the existing scheme has long flow, low recovery rate of polymerization-grade olefin, repeated arrangement of partial separation units or equipment and high investment.
Therefore, a system and a method for integrally preparing polymerization-grade olefin by DCC with carbon four comprehensive utilization are urgently needed to be provided.
Disclosure of Invention
The invention aims to provide a system and a method for integrally preparing polymerization-grade olefin by DCC (DCC) through comprehensive utilization of carbon four, aiming at the defects of the prior art. The system and the method of the invention take DCC (deep catalytic cracking), light hydrocarbon steam cracking and OCC (olefin catalytic cracking) as three heads of raw material cracking, share a set of units of fractionation, compression impurity removal and cryogenic separation to form a tail, and can prepare olefin from the raw material to the maximum extent.
In order to achieve the above object, the present invention provides, in one aspect, a system for DCC integrated preparation of polymer grade olefins with carbon four comprehensive utilization, the system comprising a DCC cracking unit, a fractionation unit, a compression impurity removal unit, a cryogenic separation unit, a steam cracking unit, an alkylation reaction unit, and an OCC cracking unit;
the DCC cracking unit, the fractionation unit, the compression impurity removal unit and the cryogenic separation unit are sequentially connected;
a first outlet of the cryogenic separation unit and a refinery liquefied gas feed pipeline are respectively connected with an inlet of the alkylation reaction unit;
a first outlet of the alkylation reaction unit is sequentially connected with inlets of the OCC cracking unit and the compression impurity removal unit;
a second outlet of the cryogenic separation unit, a second outlet of the alkylation reaction unit and a refinery propane feed pipeline are respectively connected with an inlet of the steam cracking unit, and an outlet of the steam cracking unit is connected with an inlet of the fractionation unit;
and the inlet of the compression impurity removal unit is also connected with a mixed dry gas feeding pipeline.
In another aspect, the present invention provides a method for integrally preparing polymer grade olefin by DCC with carbon four integrated utilization, which is performed in the system and comprises the following steps:
s1: feeding the reaction oil gas produced by the DCC cracking unit and the cracking gas from the steam cracking unit into the fractionating unit for fractionating treatment to obtain rich gas; feeding the rich gas, the crude propylene from the OCC unit and the mixed dry gas into the compression impurity removal unit for compression impurity removal treatment to obtain impurity-removed process gas;
s2: feeding the process gas after impurity removal into the cryogenic separation unit for cryogenic step-by-step separation treatment to obtain polymer-grade ethylene, polymer-grade propylene products, hydrogen-rich gas, methane tail gas, mixed C4, saturated alkane and crude pyrolysis gasoline;
s3: sending the mixed C4 and refinery liquefied gas into the alkylation reaction unit for alkylation treatment to obtain alkylate oil, n-butane and residual C4; sending the n-butane, the saturated alkane and refinery propane into the steam cracking unit for cracking treatment to obtain cracking gas, and sending the cracking gas into the fractionation unit;
s4: sending the residual carbon four to the OCC cracking unit for treatment to obtain the crude propylene and crude butane; feeding the crude propylene to the compression impurity removal unit.
The technical scheme of the invention has the following beneficial effects:
(1) The system and the method of the invention take DCC (deep catalytic cracking), light hydrocarbon steam cracking and OCC (olefin catalytic cracking) as three heads of raw material cracking, share a set of fractionation, compression impurity removal and cryogenic separation units to form a tail, can prepare olefin from the raw material to the maximum extent, meet the requirement of 'dry-out and clean-pressing', and can simultaneously obtain polymerization-grade ethylene and polymerization-grade propylene products, and byproducts of hydrogen-rich gas, methane tail gas, crude cracked gasoline and the like.
(2) The system and the method optimize impurity removal and separation processes, and avoid loss of the carbon two components in the dry gas recovery process. Saturated alkane (ethane/propane) separated by the cryogenic separation unit is used as a raw material to be recycled to the steam cracking unit to increase the yield of olefin; the residual carbon four obtained after alkylation treatment of the mixed carbon four separated by the cryogenic separation unit is converted into crude propylene gas by OCC (olefin catalytic cracking), the crude propylene gas and the mixed dry gas (FCC dry gas, coking dry gas and the like of a refinery) are mixed to the compression impurity removal unit, and the separation efficiency (namely the recovery rate of polymerization-grade olefin and the recovery rate of diene) are improved by compression impurity removal and cryogenic separation, so that a 'three-head-one-tail' DCC (direct Current) integrated reaction gas recovery technology for comprehensive utilization of carbon four is formed, the process of preparing ethylene by DCC (deep catalytic cracking) reaction oil gas is greatly simplified, and the recovery rate of polymerization-grade ethylene is improved from 83-92% to more than 99.6%.
(3) The invention provides a 'one-tail' separation process by simplifying the process, can save a set of equipment of units such as quenching/fractionation, stable absorption, gas separation, dry gas recovery and the like, and simplifies two-line desulfurization into one-line desulfurization, thereby forming a 'one-tail' process of fractionation, compression and separation. Therefore, the number of the devices is reduced, the investment and the occupied area are correspondingly reduced, the complexity of the operation of the device is also reduced, and the operation stability of the device is improved.
Additional features and advantages of the invention will be set forth in the detailed description which follows.
Drawings
The above and other objects, features and advantages of the present invention will become more apparent by describing in more detail exemplary embodiments thereof with reference to the attached drawings.
Figure 1 shows a process flow diagram of one prior art DCC reaction oil and gas to polymer grade olefins.
Figure 2 shows a process flow diagram for integrated preparation of polymer grade olefin by DCC with carbon four comprehensive utilization provided in example 1 of the present invention.
Detailed Description
Preferred embodiments of the present invention will be described in more detail below. While the following describes preferred embodiments of the present invention, it should be understood that the present invention may be embodied in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.
The invention provides a DCC integrated preparation polymerization grade olefin system for comprehensively utilizing C four, which comprises a DCC cracking unit, a fractionation unit, a compression impurity removal unit, a cryogenic separation unit, a steam cracking unit, an alkylation reaction unit and an OCC cracking unit;
the DCC cracking unit, the fractionation unit, the compression impurity removal unit and the cryogenic separation unit are sequentially connected;
the first outlet of the cryogenic separation unit and a refinery liquefied gas feed pipeline are respectively connected with the inlet of the alkylation reaction unit;
a first outlet of the alkylation reaction unit is sequentially connected with inlets of the OCC cracking unit and the compressed impurity removal unit;
a second outlet of the cryogenic separation unit, a second outlet of the alkylation reaction unit and a refinery propane feed pipeline are respectively connected with an inlet of the steam cracking unit, and an outlet of the steam cracking unit is connected with an inlet of the fractionation unit;
and the inlet of the compression impurity removal unit is also connected with a mixed dry gas feeding pipeline.
According to the present invention, it is preferable that,
a first outlet of the cryogenic separation unit is connected with an inlet of the alkylation reaction unit through a mixed carbon four output pipeline;
a first outlet of the alkylation reaction unit is sequentially connected with inlets of the OCC cracking unit and the compression impurity removal unit through a four-carbon-residue output pipeline;
the second export of cryrogenic separation unit through saturated alkane circulating line with the entry linkage of steam cracking unit, the second export of alkylation reaction unit through n butane output pipeline with the entry linkage of steam cracking unit.
According to the present invention, preferably, the cryogenic separation unit further comprises at least one of a cold box, a demethanizer, a deethanizer, an ethylene rectifier, a depropanizer, a propylene rectifier, a debutanizer, an ethylene machine and a propylene machine; the cryogenic separation unit is also connected with 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 pyrolysis gasoline output pipeline.
According to the present invention, preferably, the third outlet of the alkylation reaction unit is connected to an alkylate oil outlet line.
According to the invention, the OCC cracking unit is preferably also connected to a crude butane output line.
According to the present invention, preferably, the fractionation unit is further connected to a heavies output line.
According to the present invention, preferably, the compression and impurity removal unit includes at least one of a compressor, an amine wash/caustic wash tower and a impurity removal adsorption bed.
According to the invention, preferably, a selective hydrogenation device is arranged between the cryogenic separation unit and the alkylation reaction unit. In the invention, if the content of the dialkene and the alkyne in the mixed C4 is higher, a C4 selective hydrogenation device is required to meet the feeding requirement of alkylation.
In another aspect, the present invention provides a method for integrally preparing polymer grade olefin by DCC with carbon four integrated utilization, which is performed in the system and comprises the following steps:
s1: feeding the reaction oil gas produced by the DCC cracking unit and the cracking gas from the steam cracking unit into the fractionating unit for fractionating treatment to obtain rich gas; feeding the rich gas, the crude propylene from the OCC unit and the mixed dry gas into the compression impurity removal unit for compression impurity removal treatment to obtain impurity-removed process gas;
s2: feeding the process gas after impurity removal into the cryogenic separation unit for cryogenic step-by-step separation treatment to obtain polymer-grade ethylene, polymer-grade propylene products, hydrogen-rich gas, methane tail gas, mixed C4, saturated alkane and crude pyrolysis gasoline;
s3: sending the mixed C4 and refinery liquefied gas into the alkylation reaction unit for alkylation treatment to obtain alkylate oil, n-butane and residual C4; sending the n-butane, the saturated alkane and refinery propane into the steam cracking unit for cracking treatment to obtain cracking gas, and sending the cracking gas into the fractionation unit; the alkylate is used directly as a gasoline product;
s4: sending the residual carbon four into the OCC cracking unit for treatment to obtain the crude propylene and crude butane; and feeding the crude propylene to the compression impurity removal unit.
According to the present invention, preferably, the feedstock in the DCC cracking unit is hydrogenated wax oil and/or hydrogenated heavy oil.
According to the invention, preferably, substances removed by the gas in the fractionating unit after the fractionating treatment are heavy components with the distillation range of more than or equal to 150 ℃, and preferably, the substances removed by the fractionating unit comprise coke, oil slurry, diesel oil and pyrolysis gasoline.
According to the invention, preferably, after the gas in the compression impurity removal unit is subjected to the compression impurity removal treatment, the removed impurities comprise CO 2 、H 2 S、NO x Organic sulfur, arsenic and mercury.
According to the invention, preferably, the content of impurities in the gas treated by the compression impurity removal unit is less than or equal to 1ppm.
According to the present invention, it is preferable that the outlet pressure of the compressor in the compression impurity removing unit is 3 to 4MPaG.
According to the present invention, preferably, the dry gas mixture is refinery FCC dry gas and/or coker dry gas.
According to the invention, preferably, the refrigeration capacity of the cryogenic separation unit is provided by the cascade refrigeration of an ethylene machine and a propylene machine.
According to the invention, preferably, the hydrogen-methane tail gas in the cryogenic separation unit is separated at a temperature of-160 to-165 ℃ to obtain the hydrogen-rich gas and a part of the methane tail gas in the methane tail gas.
According to the present invention, preferably, the hydrogen-rich gas contains H 2 /N 2 The purity is 94-96mol%.
According to the present invention, preferably, the remaining methane tail gas in the methane tail gas is from the demethanizer overhead gas phase.
In the cryogenic separation unit of the invention, as a preferable scheme, the methane-hydrogen tail gas is separated from the hydrogen-rich gas at-163 ℃, so that the hydrogen-rich gas with higher added value, namely H, is obtained 2 /N 2 95mol percent, compared with the prior process, the method can recover the hydrogen to the maximum extent without Pressure Swing Adsorption (PSA), and reduce a large amount of hydrogen lost along with methane hydrogen tail gas in a dry gas recovery unit.
According to the present invention, it is preferable that the recovery rate of polymerization-grade olefins is 99.6% or more; the yield of the diene is improved by 45 to 55 percent.
In the invention, DCC (deep catalytic cracking), light hydrocarbon steam cracking (namely a steam cracking unit) and OCC (olefin catalytic cracking) are used as three ends of raw material cracking, heavy components such as coke, slurry oil, diesel oil, cracked gasoline and the like are removed from oil gas generated by DCC cracking and cracked gas generated by light hydrocarbon steam cracking through a fractionating unit to obtain rich gas, and the rich gas, crude propylene gas from OCC (olefin catalytic cracking) and mixed dry gas are subjected to compression, impurity removal, cryogenic separation and other operations through a compression impurity removal unit and a cryogenic separation unit to separate polymerization-grade ethylene and polymerization-grade propylene products to form a tail. The components and molecular weights of crude propylene gas and mixed dry gas (refinery FCC dry gas, coking dry gas and the like) from OCC (olefin catalytic cracking) are similar to those of rich gas, meanwhile, the gas phase quantity is small relative to DCC, and the gas phase quantity can be merged into a compression unit together to be mixed with the rich gas, so that the subsequent separation system flow and equipment setting are not greatly influenced, and the comprehensive utilization efficiency of resources and the recovery rate of olefin can be improved by removing impurities and recovering olefin together.
In the invention, as the DCC (deep catalytic cracking) raw material is heavy oil such as hydrogenated wax oil and/or hydrogenated heavy oil, saturated alkane (ethane/propane) contained in the cracked reaction oil gas can not be used as the raw material of catalytic cracking after final separation, and olefin is prepared by further cracking through a steam cracking unit. In addition, the mixed C4 and refinery liquefied gas obtained by the separation of the cryogenic separation unit are used as alkylation raw materials and are alkylated to obtain n-butane, residual C-tetraolefin and alkylate oil, wherein: the alkylate is directly used as a gasoline product; saturated alkanes such as ethane/propane and the like obtained by the deep cooling separation of normal butane and refinery propane are used as cracking raw materials and are circulated to a steam cracking unit for light hydrocarbon steam cracking to prepare cracking gas, and the cracking gas is merged into oil gas cracked by DCC; the residual carbon tetraolefin is processed by OCC (olefin catalytic cracking) to produce crude propylene and byproduct crude butane, and the crude propylene, mixed dry gas and rich gas are mixed to enter compression for impurity removal. The invention greatly simplifies the process of recovering ethylene from DCC reaction gas by deep catalytic cracking, improves the yield of diene by 45-55 percent, improves the recovery rate of olefin from 83-92 percent to more than 99.6 percent, improves the comprehensive utilization efficiency of crude propylene prepared by mixing C4, simplifies the process unit flow, reduces the investment cost and ensures that the final product structure does not contain ethane/propane/butane and other alkanes.
The system and method of the present invention avoids the loss of the carbon dioxide component of the dry gas recovery unit. In the existing process, in order to recover ethylene in dry gas, methane hydrogen tail gas needs to be removed through a dry gas recovery unit to obtain concentrated mixed carbon dioxide dry gas, the process usually adopts oil absorption or PSA and other modes, and 8-17% of carbon dioxide components are mixed in the methane tail gas and cannot be recovered. The cryogenic separation rectification operation can well control the separation index of the rectification tower at a lower operation temperature, improve the recovery rate of polymer-grade ethylene and polymer-grade propylene while obtaining the polymer-grade ethylene and the polymer-grade propylene, reduce the loss of saturated alkane such as ethane/propane and the like, and greatly improve the diene yield of the device.
The system and the method of the invention simplify the separation process and reduce the investment of the device. In the existing process, two separation processes are needed, one separation process is used for separating DCC reaction oil gas, light gas and liquid phases are obtained through oil absorption processes such as fractionation, stable absorption and the like, and LPG and dry gas are obtained after organic sulfur and inorganic sulfur are removed through double removal. LPG is subjected to gas separation to obtain propylene, and the propylene is further refined according to the requirements of downstream devices; the dry gas can enter cryogenic separation after being pretreated by dry gas recovery and the like, so that a polymer-grade ethylene product is obtained. After ethane/propane is circulated to a cracking furnace for cracking, the ethane/propane is subjected to quenching and compression and also subjected to cryogenic separation, so that the ethane/propane can be eaten and squeezed completely. By adopting the 'one-tail' separation process, the reaction oil gas cracked by DCC and the cracked gas cracked by light hydrocarbon steam are sent to a fractionation unit together, and rich gas is obtained after heavy components such as diesel oil, cracked gasoline and the like are removed; the rich gas, crude propylene gas from OCC (olefin catalytic cracking) and mixed dry gas are pressurized by a compressor to remove CO 2 、H 2 S、NO x Organic sulfur, arsenic, mercury and other impurities, and finally separating the impurities step by step in a cryogenic separation unit to obtain polymer-grade ethylene and polymer-grade propyleneAlkene products, and saturated alkanes such as ethane/propane and the like are directly circulated to a light hydrocarbon cracking furnace (steam cracking unit) in the 'three-head' for cracking, so that the separation process is greatly simplified, and meanwhile, on the aspect of product purity, no further refining is needed, and the product can be directly used as raw materials for downstream polyolefin devices, EOEG devices and the like.
The present invention is specifically described below by way of examples.
Example 1
The embodiment provides a system for preparing polymerization-grade olefin by integrating DCC (DCC) with comprehensive utilization of carbon four, which comprises a DCC cracking unit, a fractionation unit, a compression impurity removal unit, a cryogenic separation unit, a steam cracking unit, an alkylation reaction unit and an OCC cracking unit, as shown in the process flow of FIG. 2;
the DCC cracking unit, the fractionation unit, the compression impurity removal unit and the cryogenic separation unit are sequentially connected;
a first outlet of the cryogenic separation unit is connected with an inlet of the alkylation reaction unit through a mixed carbon four output pipeline; the inlet of the alkylation reaction unit is also connected with a refinery liquefied gas feeding pipeline;
a first outlet of the alkylation reaction unit is sequentially connected with inlets of the OCC cracking unit and the compression impurity removal unit through a four-carbon-residue output pipeline;
a second outlet of the cryogenic separation unit is connected with an inlet of the steam cracking unit through a saturated alkane circulating pipeline, and a second outlet of the alkylation reaction unit is connected with an inlet of the steam cracking unit through a normal butane output pipeline; the inlet of the steam cracking unit is also connected with a refinery propane feeding pipeline;
the cryogenic separation unit also comprises other outlets, an ethylene machine and a propylene machine; and the other outlets are respectively connected with a hydrogen-rich gas output pipeline, a methane tail gas output pipeline, a polymerization stage ethylene output pipeline, a polymerization stage propylene output pipeline and a crude pyrolysis gasoline output pipeline. A third gas outlet of the alkylation reaction unit is connected with an alkylate oil output pipeline;
the outlet of the steam cracking unit is connected with the inlet of the fractionation unit;
and the inlet of the compression impurity removal unit is also connected with a mixed dry gas feeding pipeline. The compression impurity removal unit comprises a compressor and an impurity removal adsorption bed.
The OCC cracking unit is also connected with a crude butane output pipeline;
the fractionating unit is also connected to a heavies output line.
The DCC integrated preparation method for polymerization grade olefin by utilizing the carbon four in the system comprises the following steps:
s1: hydrogenated heavy oil is used as a raw material of the DCC cracking unit, reaction oil gas produced by the DCC cracking unit and cracking gas from the steam cracking unit are sent to the fractionating unit for fractionating treatment, and heavy components such as coke, oil slurry, diesel oil and cracking gasoline are removed to obtain rich gas; sending the rich gas, the crude propylene from the OCC unit and the mixed dry gas into the compression impurity removal unit for compression impurity removal treatment to remove CO 2 、H 2 S、NO x Organic sulfur, arsenic, mercury and other impurities to obtain process gas after impurity removal; the content of impurities in the gas treated by the compression impurity removal unit is less than or equal to 1ppm; the mixed dry gas is FCC dry gas and coking dry gas of a refinery.
S2: feeding the process gas after impurity removal into the cryogenic separation unit for cryogenic step-by-step separation treatment to obtain polymer-grade ethylene, polymer-grade propylene products, hydrogen-rich gas, methane tail gas, mixed C4, saturated alkane and crude pyrolysis gasoline; wherein, the cold energy of the cryogenic separation unit is provided by the cascade refrigeration of an ethylene machine and a propylene machine; separating methane tail gas and hydrogen-rich gas from methane-hydrogen tail gas at-163 deg.C to obtain hydrogen-rich gas with high added value, i.e. H 2 /N 2 95mol%, and a portion of the methane tail gas in the methane tail gas, the remaining methane tail gas being from the demethanizer overhead gas phase.
S3: sending the mixed C4 and refinery liquefied gas into the alkylation reaction unit for alkylation treatment to obtain alkylate oil, n-butane and residual C4; sending the n-butane, the saturated alkane and refinery propane into the steam cracking unit for cracking treatment to obtain cracking gas, and sending the cracking gas into the fractionation unit; the alkylate is directly used as a gasoline product;
s4: sending the residual carbon four to the OCC cracking unit for treatment to obtain the crude propylene and crude butane; feeding the crude propylene to the compression impurity removal unit.
The yield of the ethylene obtained by the system and the method of the embodiment is improved to more than 11 percent from 3.6 percent, the yield of the propylene is improved to 19 percent from 16 percent, namely the yield of the diene is improved by 53 percent, and the recovery rate of the polymerization grade olefin is more than 99.6 percent.
While embodiments of the present invention have been described above, the above description is illustrative, not exhaustive, and not limited to the disclosed embodiments. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments.
Claims (10)
1. A DCC integrated polymerization-grade olefin system for comprehensively utilizing carbon four is characterized by comprising a DCC cracking unit, a fractionation unit, a compression impurity removal unit, a cryogenic separation unit, a steam cracking unit, an alkylation reaction unit and an OCC cracking unit;
the DCC cracking unit, the fractionation unit, the compression impurity removal unit and the cryogenic separation unit are sequentially connected;
the first outlet of the cryogenic separation unit and a refinery liquefied gas feed pipeline are respectively connected with the inlet of the alkylation reaction unit;
a first outlet of the alkylation reaction unit is sequentially connected with inlets of the OCC cracking unit and the compression impurity removal unit;
a second outlet of the cryogenic separation unit, a second outlet of the alkylation reaction unit and a refinery propane feed pipeline are respectively connected with an inlet of the steam cracking unit, and an outlet of the steam cracking unit is connected with an inlet of the fractionation unit;
and the inlet of the compression impurity removal unit is also connected with a mixed dry gas feeding pipeline.
2. The system for integrated preparation of polymer grade olefins according to claim 1, wherein,
a first outlet of the cryogenic separation unit is connected with an inlet of the alkylation reaction unit through a mixed carbon four output pipeline;
a first outlet of the alkylation reaction unit is sequentially connected with inlets of the OCC cracking unit and the compression impurity removal unit through a four-carbon-residue output pipeline;
a second outlet of the cryogenic separation unit is connected with an inlet of the steam cracking unit through a saturated alkane circulating pipeline, and a second outlet of the alkylation reaction unit is connected with an inlet of the steam cracking unit through a normal butane output pipeline;
the cryogenic separation unit also comprises at least one of a cold box, a demethanizer, a deethanizer, an ethylene rectifying tower, a depropanizer, a propylene rectifying tower, a debutanizer, an ethylene machine and a propylene machine; the cryogenic separation unit is also connected with 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 pyrolysis gasoline output pipeline.
3. The system for integrated preparation of polymer grade olefins according to claim 1, wherein,
a third outlet of the alkylation reaction unit is connected with an alkylate oil output pipeline;
the OCC cracking unit is also connected with a crude butane output pipeline;
the fractionation unit is also connected to a heavies output line.
4. The system for integrated DCC production of polymer grade olefins according to claim 1, wherein the compressed impurity removal unit comprises at least one of a compressor, an amine wash/caustic wash tower, and a de-impurity adsorption bed.
5. The system for integrally preparing polymerization-grade olefin by DCC according to any one of claims 1 to 4, wherein a selective hydrogenation device is arranged between the cryogenic separation unit and the alkylation reaction unit.
6. A process for the integrated preparation of polymer grade olefins by carbon four integrated DCC, wherein the process is carried out in the system of any of claims 1 to 5, comprising the steps of:
s1: feeding the reaction oil gas produced by the DCC cracking unit and the cracking gas from the steam cracking unit into the fractionating unit for fractionating treatment to obtain rich gas; feeding the rich gas, the crude propylene from the OCC unit and the mixed dry gas into the compression impurity removal unit for compression impurity removal treatment to obtain impurity-removed process gas;
s2: feeding the process gas after impurity removal into the cryogenic separation unit for cryogenic step-by-step separation treatment to obtain polymer-grade ethylene, polymer-grade propylene products, hydrogen-rich gas, methane tail gas, mixed C4, saturated alkane and crude pyrolysis gasoline;
s3: sending the mixed C4 and refinery liquefied gas into the alkylation reaction unit for alkylation treatment to obtain alkylate oil, n-butane and residual C4; sending the n-butane, the saturated alkane and the refinery propane into the steam cracking unit for cracking treatment to obtain cracking gas, and sending the cracking gas into the fractionation unit;
s4: sending the residual carbon four to the OCC cracking unit for treatment to obtain the crude propylene and crude butane; feeding the crude propylene to the compression impurity removal unit.
7. The integrated DCC process of polymer grade olefins according to claim 6, wherein the feedstock in the DCC cracking unit is hydrogenated wax oil and/or hydrogenated heavy oil.
8. The integrated DCC process of claim 6, wherein,
after the gas in the fractionating unit is subjected to the fractionating treatment, the removed substances are heavy components with the distillation range of more than or equal to 150 ℃, and preferably, the substances removed by the fractionating unit comprise coke, slurry oil, diesel oil and pyrolysis gasoline;
after the gas in the compression impurity removal unit is subjected to compression impurity removal treatment, the removed impurities comprise CO 2 、H 2 S、NO x Organic sulfur, arsenic and mercury; the content of impurities in the gas treated by the compression impurity removal unit is less than or equal to 1ppm;
the outlet pressure of a compressor in the compression impurity removal unit is 3-4 MPaG;
the mixed dry gas is refinery FCC dry gas and/or coking dry gas.
9. The integrated DCC process for the preparation of polymer grade olefins according to claim 6, wherein,
the cold energy of the cryogenic separation unit is provided by cascade refrigeration of an ethylene machine and a propylene machine;
separating the methane-hydrogen tail gas in the cryogenic separation unit at the temperature of-160 to-165 ℃ to obtain the hydrogen-rich gas and a part of methane tail gas in the methane tail gas;
h in the hydrogen-rich gas 2 /N 2 The purity is 94-96mol%;
the remaining methane tail gas in the methane tail gas is from the demethanizer overhead gas phase.
10. The integrated DCC-based polymerization grade olefin production method according to any one of claims 6 to 9, wherein the recovery rate of the polymerization grade olefin is 99.6% or more; the yield of the diene is improved by 45 to 55 percent.
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