Separation apparatus and method for carbon three fraction in propane dehydrogenation to propylene gas phase product

Abstract

The application discloses a separation device and method for carbon three fraction in propane dehydrogenation to propylene gas phase product, which comprises a cold box sequence, a carbon three booster pump, a liquid separation tank, a light component flash tower and a fractional condensation tower; the device is connected into a closed loop for separating the gas phase product by using its own cold energy; the cold box sequence comprises a first stage cold box, a second stage cold box, a third stage cold box and a fourth stage cold box, and at least two stage cold boxes are provided with a mixer and a circulating propane supplement inlet. In the technical scheme, the cold energy required by the cold energy gas is provided by the throttling expansion of the gas phase product itself, the circulating propane is quantitatively and batch mixed with a part of the cold energy gas to provide the cold energy for the carbon three separation of the gas phase product, and the mixed refrigerant refrigerator is provided to supplement the cold energy for the hydrogen separation. The technical scheme can reduce the heat exchange area by about 16%, effectively reduce the power of the mixed refrigerant compressor by 27.8%, and achieve the purpose of fully recovering the propylene product in advance of reducing the equipment investment.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of chemical industry, more particularly, relates to a kind of propane dehydrogenation to prepare propylene gas phase product carbon three fraction separation device and method. BACKGROUND

[0002] Propylene is an important petrochemical basic raw material, downstream products mainly include polypropylene, propylene oxide, cumene / phenol / acetone / bisphenol A, acrylic acid and ester, epichlorohydrin, etc. In recent years, the global propylene demand grows rapidly, and the propylene produced by traditional processes such as naphtha cracking and refinery catalytic cracking is difficult to keep up with the rapid growth pace of demand. Among a few large-scale propylene production processes, propane dehydrogenation (PDH) has been proven to be the most effective way to solve the source of propylene. The propane dehydrogenation gas phase product contains a large amount of light component gases such as hydrogen, alkane, etc., which usually need to be sent to a cryogenic processing unit for low-temperature separation.

[0003] How to economically and effectively separate the carbon three fraction generated by propane dehydrogenation reaction from the light component is the core of the entire propane dehydrogenation separation process. Cryogenic separation requires a large amount of energy consumption and the use of a large-sized cryogenic heat exchanger. The method of expansion refrigeration is usually used, which requires the use of expensive cryogenic expanders. Due to the large flow of light components, low separation temperature and high speed, it brings great difficulty to the design and manufacture of cryogenic expanders. SUMMARY

[0004] The inventors found in the research that in the process of separating hydrogen from propane dehydrogenation gas phase product, the reaction diluent hydrogen can be mixed with the reaction raw material propane (containing fresh propane and recycled propane) in batches to provide cold energy for the cold box, separate hydrogen from propylene product in the gas phase product, and use mixed refrigerant refrigeration to provide cold energy for separating hydrogen. The purpose of the present application is to provide a propane dehydrogenation to prepare propylene gas phase product separation device and separation method. In the technical scheme, the heat exchange between the gas phase product and the reaction product is fully utilized, mixed refrigerant refrigeration is used, low-temperature separation of the gas phase product is realized, and the purpose of fully recovering propylene product is achieved.

[0005] In order to achieve the above purpose, the first aspect of the present application provides a kind of propane dehydrogenation to prepare propylene gas phase product carbon three fraction separation device, the device includes: cold box sequence, carbon three booster pump, liquid separation tank, light component flash tower, partial condensation fractionating column;

[0006] The cold box sequence includes a first-stage cold box, a second-stage cold box, a third-stage cold box and a fourth-stage cold box.

[0007] The liquid separation tank includes a first liquid separation tank, a second liquid separation tank and a partial condensation fractionating column.

[0008] The gas phase product feed pipeline is connected with the first-stage cold box, the second-stage cold box, the third-stage cold box and the first liquid separator in sequence;

[0009] The top of the first liquid separator is connected with the fourth-stage cold box and the second liquid separator in sequence; the bottom is connected with the lower inlet of the light component flash tower;

[0010] The top of the second liquid separator is connected with the lower part of the fractional condensation fractionating tower; the bottom is connected with the middle part of the light component flash tower;

[0011] The top of the fractional condensation fractionating tower is divided into two branches after being connected with the fourth-stage cold box; one branch is connected with the third-stage cold box, the second-stage cold box, the first-stage cold box and the crude hydrogen outlet pipeline in sequence; the other branch is connected with the third-stage cold box, the second-stage cold box, the first-stage cold box and the reactor feed outlet pipeline in sequence; the bottom is connected with the upper inlet of the light component flash tower;

[0012] The top of the light component flash tower is provided with a gas phase outlet pipeline; the bottom is connected with the carbon three booster pump, the third-stage cold box, the second-stage cold box, the first-stage cold box and the carbon three fraction outlet pipeline in sequence;

[0013] The circulating propane feed pipeline is connected with the first-stage cold box, the second-stage cold box and the third-stage cold box in sequence; the circulating propane pipeline at the outlet of at least two cold boxes and the reactor feed pipeline at the inlet are connected through interconnecting pipelines; a mixer and a circulating propane supplement inlet are arranged on each interconnecting pipeline.

[0014] The second aspect of the present application provides a separation method of the carbon three fraction in the gas phase product of the propane dehydrogenation to propylene; the method comprises the following steps:

[0015] (1) the gas phase product from the deep purification unit is sent into the cold box sequence through the gas phase product feed pipeline, and is cooled to-90℃ to-110℃ in the first-stage cold box, the second-stage cold box and the third-stage cold box in sequence to obtain a cooled gas phase product;

[0016] (2) the cooled gas phase product is subjected to gas-liquid separation in the first liquid separator; the liquid phase at the bottom is sent into the lower part of the light component flash tower; the gas phase at the top is sent into the fourth-stage cold box and is cooled to-110℃ to-130℃ to obtain a deep cooling gas phase product;

[0017] (3) the deep cooling gas phase product is sent into the second liquid separator and is subjected to gas-liquid separation; the liquid phase at the bottom is sent into the middle part of the light component flash tower; the gas phase at the top is sent into the lower part of the fractional condensation fractionating tower and is subjected to gas-liquid separation; the liquid phase at the bottom after the gas-liquid separation is sent into the upper part of the light component flash tower; the gas phase at the top is returned to the fourth-stage cold box to recover cold energy and then a cold energy recovery gas phase is obtained;

[0018] (4) The cold recovery gas phase is divided into two parts, one part of the gas phase sequentially passes through the three-stage cold box, the two-stage cold box and the one-stage cold box to recover cold in stages to obtain crude hydrogen and is extracted through a crude hydrogen extraction pipeline; the other part of the gas phase sequentially enters the three-stage cold box, the two-stage cold box and the one-stage cold box, and is mixed with countercurrent circulating propane and optional make-up circulating propane added through a make-up circulating propane inlet in a mixer before entering the inlet of each cold box, and the cold gas recovered through cold recovery in stages is extracted through a reactor feed pipeline;

[0019] (5) The overhead gas phase of the light component flash tower is extracted through a gas phase extraction pipeline, and the liquid phase at the bottom is pressurized by a carbon three booster pump and then sent to the cold box sequence, and cold recovery is performed in the three-stage cold box, the two-stage cold box and the one-stage cold box to obtain a carbon three fraction, which is extracted through a carbon three fraction extraction pipeline.

[0020] The effects of the present application are as follows:

[0021] (1) In the technical solution of the present application, an expensive expander is not needed, heat exchange between the gas phase product and the reaction product is fully utilized, low-temperature separation of the gas phase product is realized, insufficient cold is provided by the mixed refrigerant chiller unit, and the purpose of fully recovering propylene product is achieved.

[0022] (2) In the technical solution provided by the present application, the gas phase product itself provides the cold required for the expansion of the cold gas, and the circulating propane is quantitatively and batchwise mixed with a part of the cold gas to provide cold for the carbon three separation of the gas phase product. This technical solution can reduce the heat exchange area by about 16% and can provide a lower temperature, thereby achieving the purpose of fully recovering propylene product while reducing equipment investment.

[0023] (3) In the present application, through reasonable distribution of cold, the cold box exhibits excellent heat transfer performance, the minimum heat transfer temperature difference at the low-temperature end is greater than 3°C, the heat transfer temperature difference at the hot end is greater than 3°C, the heat transfer area (UA value) is smaller, and the heat exchange area is reduced by 16%.

[0024] (4) Compared with the refrigeration scheme in which propane is mixed only once, the present application can reduce the power consumption of the mixed refrigerant compressor by 27.8%.

[0025] Other features and advantages of the present application will be described in detail in the following specific embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0026] The above and other objects, features and advantages of the present application will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings in which like reference characters refer to like parts throughout the several views, and in which:

[0027] Figure 1A schematic diagram of a C3 fraction separation process in Example 1 of the present application is shown.

[0028] Figure 2 A schematic diagram of a C3 fraction separation process in Example 2 of the present application is shown.

[0029] Figure 3 A schematic diagram of a C3 fraction separation process in Comparative Example 1 of the present application is shown.

[0030] BRIEF DESCRIPTION OF DRAWINGS

[0031] E-301X, primary cold box; E-302X, secondary cold box; E-303X, tertiary cold box; E-304X, quaternary cold box; E-305X, condenser of the fractionating column; D-301, first knock-out drum; D-302, second knock-out drum; D-310, first mixed refrigerant knock-out drum; D-320, second mixed refrigerant knock-out drum; P-301, C3 booster pump; P-310, first mixed refrigerant booster pump; P-320, second mixed refrigerant booster pump; C-301, light component flash tower; C-302, fractionating column; B-301, primary cold box circulating propane make-up inlet; B-302, secondary cold box circulating propane make-up inlet; B-303, tertiary cold box circulating propane make-up inlet; M-301, primary cold box mixer; M-302, secondary cold box mixer; M-303, tertiary cold box mixer; DH-301, first knock-out drum flow control valve; DH-302, second knock-out drum flow control valve; CH-302, fractionating column flow control valve; K-310, mixed refrigerant compressor first stage; K-320, mixed refrigerant compressor second stage; E-310, first mixed refrigerant water cooler; E-320, second mixed refrigerant water cooler. DETAILED DESCRIPTION

[0032] Preferred embodiments of the present application will be described in more detail below. Although the preferred embodiments of the present application are described below, it is understood that the present application can be implemented in various forms and should not be limited by the embodiments set forth herein.

[0033] The present application provides a device for separating a C3 fraction from a propane dehydrogenation gas phase product, as shown in Figure 1 The device includes a cold box sequence, a mixed refrigerant refrigerator, a C3 booster pump P-301, a knock-out drum, a light component flash tower C-301, and a fractionating column C-302.

[0034] The cold box sequence includes a primary cold box E-301X, a secondary cold box E-302X, a tertiary cold box E-303X, and a quaternary cold box E-304X.

[0035] The liquid separation tank includes a first liquid separation tank D-301, a second liquid separation tank D-302, and a fractionation column C-302;

[0036] The gaseous product feed pipeline is connected to the first-stage cold box E-301X, the second-stage cold box E-302X, the third-stage cold box E-303X, and the first liquid separation tank D-301 in sequence.

[0037] The first liquid separation tank D-301 is connected to the fourth-stage cold box E-304X and the second liquid separation tank D-302 in sequence at the top, and is connected to the lower inlet of the light component flash tower C-301 at the bottom.

[0038] The second liquid separation tank D-302 is connected to the fractionation column C-302 at the top, and is connected to the middle of the light component flash tower C-301 at the bottom.

[0039] The fractionation column C-302 is divided into two branches at the top after being connected to the fourth-stage cold box E-304X, one branch is connected to the third-stage cold box E-303X, the second-stage cold box E-302X, the first-stage cold box E-301X, and the crude hydrogen outlet pipeline in sequence, and the other branch is connected to the third-stage cold box E-303X, the second-stage cold box E-302X, the first-stage cold box E-301X, and the reactor feed outlet pipeline in sequence, and the bottom is connected to the upper inlet of the light component flash tower C-301.

[0040] The light component flash tower C-301 is provided with a gaseous product outlet pipeline at the top, and is connected to the third-stage cold box E-303X, the second-stage cold box E-302X, the first-stage cold box E-301X, and the carbon three fraction outlet pipeline in sequence at the bottom.

[0041] The circulating propane feed pipeline is connected to the first-stage cold box E-301X, the second-stage cold box E-302X, and the third-stage cold box E-303X in sequence, and the circulating propane pipeline at the outlet of at least two stages of the cold box and the reactor feed pipeline at the inlet are connected through an interconnecting pipeline, and a mixer and a circulating propane supplement inlet are arranged on each interconnecting pipeline.

[0042] Preferably, the device further comprises a mixed refrigerant refrigerator.

[0043] The mixed refrigerant refrigerator comprises a mixed refrigerant compressor section K-310, a mixed refrigerant first water cooler E-310, a mixed refrigerant first liquid separation tank D-310, a mixed refrigerant compressor section K-320, a mixed refrigerant second water cooler E-320, and a mixed refrigerant second liquid separation tank D-320 connected in sequence.

[0044] The bottom of the mixed refrigerant first liquid separation tank D-310 is connected to the mixed refrigerant second liquid separation tank feed pipeline through a mixed refrigerant first booster pump P-310, and the bottom of the mixed refrigerant second liquid separation tank D-320 is connected to the mixed refrigerant outlet pipeline at the top through a mixed refrigerant second booster pump P-320.

[0045] The split fractionating column C-302 is provided with a split fractionating column condenser E-305X;

[0046] The mixed refrigerant refrigerator outlet is connected to the first cold box E-301X, the second cold box E-302X, the third cold box E-303X, the fourth cold box E-304X and the split fractionating column condenser E-305X inlet in sequence; the split fractionating column condenser E-305X outlet is connected to the fourth cold box E-304X, the third cold box E-303X, the second cold box E-303X and the first cold box E-303X, and the mixed refrigerant refrigerator inlet in sequence.

[0047] According to the present application, each of the interconnecting pipelines is provided with at least one circulating propane supplement inlet and a mixer, and the circulating propane supplement inlet and the mixer are independently controlled.

[0048] The bottom of the liquid separation tank is provided with a flow control valve, and the flow control valve is independently controlled.

[0049] The present application also provides a method for separating carbon three fractions in a propane dehydrogenation propylene gas phase product, which comprises the following steps:

[0050] (1) The gas phase product from the deep purification unit is sent into the cold box sequence through the gas phase product feed pipeline, and is cooled to -90℃ to -110℃ in the first cold box E-301X, the second cold box E-302X and the third cold box E-303X to obtain a cooled gas phase product;

[0051] (2) The cooled gas phase product is subjected to gas-liquid separation in the first liquid separation tank D-301, and the tank bottom liquid phase is sent into the lower part of the light component flash tower C-301, and the tank top gas phase is sent into the fourth cold box E-304X and cooled to -110℃ to -130℃ to obtain a deep cooling gas phase product;

[0052] (3) The deep cooling gas phase product is sent into the second liquid separation tank D-302 for gas-liquid separation, and the tank bottom liquid phase is sent into the middle part of the light component flash tower C-301, and the tank top gas phase is sent into the lower part of the split fractionating column C-302 for gas-liquid separation, and the bottom liquid phase after gas-liquid separation is sent into the upper part of the light component flash tower C-301, and the top gas phase is returned to the fourth cold box E-304X to recover cold energy to obtain a cold energy recovery gas phase;

[0053] (4) The cold recovery gas phase is divided into two parts, one part of the gas phase sequentially passes through the three-stage cold box E-303X, the two-stage cold box E-302X and the one-stage cold box E-301X to recover cold in stages to obtain crude hydrogen and is extracted through a crude hydrogen extraction pipeline; the other part of the gas phase sequentially enters the three-stage cold box E-303X, the two-stage cold box E-302X and the one-stage cold box E-301X, and before entering the inlet of each cold box, is mixed with countercurrent circulating propane and optionally added circulating propane from a circulating propane supplement inlet in a mixer, and the cold gas recovered by the cold recovery in stages is extracted through a reactor feed pipeline;

[0054] (5) The overhead gas phase of the light component flash tower C-301 is extracted through a gas phase extraction pipeline, and the bottom liquid phase is pressurized by a carbon three booster pump P-301 and then sent to the cold box sequence to recover cold in the three-stage cold box E-303X, the two-stage cold box E-302X and the one-stage cold box E-301X to obtain a carbon three fraction, which is extracted through a carbon three fraction extraction pipeline.

[0055] Preferably, the method further comprises:

[0056] (6) The mixed refrigerant is sent to the cold box sequence through the mixed refrigerant refrigerator outlet after two-stage pressurization and water cooling in the mixed refrigerant refrigerator, and is sequentially cooled to -123℃ to -143℃ in the one-stage cold box E-301X, the two-stage cold box E-302X, the three-stage cold box E-303X and the four-stage cold box E-304X to provide cold for the azeotrope fractional distillation column condenser E-305X, and then returns to the four-stage cold box E-304X, the three-stage cold box E-303X, the two-stage cold box E-302X and the one-stage cold box E-301X to provide cold for the cold box sequence and then returns to the mixed refrigerant refrigerator inlet.

[0057] According to the present application, the number of circulating propane supplement inlets is not less than 2.

[0058] In the present application, the circulating propane includes newly added circulating propane and circulating propane in the cold box, and the ratio of the two is set by the reaction unit.

[0059] The gas phase product liquefaction rate changes greatly above -40℃, and most of the carbon three components have been condensed at around -40℃. After further cooling, the condensation rate slows down due to the high hydrogen content in the gas phase and the low carbon three component partial pressure, and the condensation amount changes little after cooling to below -100℃.

[0060] The liquid phase of the first liquid separator D-301, the liquid phase of the second liquid separator D-302 and the liquid phase of the azeotrope fractional distillation column C-302 enter the light component flash tower C-301 for separation, respectively.

[0061] The cold of the crude hydrogen product at the top of the azeotrope fractional distillation column C-302 is used to cool the cryogenic gas phase product to recover cold.

[0062] The separation of hydrogen from the C3 fraction is achieved in a fractionation column C-302, which is cooled by the mixed refrigerant.

[0063] Preferably, the tertiary cold box, the secondary cold box and the primary cold box are fed with make-up recycle propane.

[0064] The tertiary cold box is fed with make-up recycle propane at a temperature of -110°C to -90°C, preferably 5% to 12% of the total amount of recycle propane.

[0065] The secondary cold box is fed with make-up recycle propane at a temperature of -90°C to -40°C, preferably 12% to 18% of the total amount of recycle propane.

[0066] The primary cold box is fed with make-up recycle propane at a temperature of -60°C to -0°C, preferably 70% to 83% of the total amount of recycle propane.

[0067] According to a preferred embodiment of the present application, the tertiary cold box and the primary cold box are fed with make-up recycle propane.

[0068] The tertiary cold box is fed with make-up recycle propane at a temperature of -110°C to -90°C, preferably 5% to 40% of the total amount of recycle propane.

[0069] The primary cold box is fed with make-up recycle propane at a temperature of -90°C to 0°C, preferably 60% to 85% of the total amount of recycle propane.

[0070] According to the present application, the mass ratio of the gaseous product fed to the C3 fraction withdrawn is 0.5 to 2:1, preferably 0.8 to 1.35:1.

[0071] According to the present application, the operating pressure at the inlet of the mixed refrigerant refrigerator is 0.15 to 0.32 MPaG, preferably 0.19 to 0.28 MPaG.

[0072] The operating pressure at the outlet of the mixed refrigerant refrigerator is 2.8 to 4.1 MPaG, preferably 3.1 to 3.7 MPaG.

[0073] The operating temperature of the C3 booster pump is -90 to -115°C and the operating pressure is 1.7 to 4.3 MPaG.

[0074] The operating pressure of the first mixed refrigerant booster pump is 2.8 to 4.1 MPaG, preferably 3.1 to 3.6 MPaG;

[0075] The operating pressure of the mixed refrigerant second booster pump is 2.9-4.3 MPaG, preferably 3.6-3.9 MPaG;

[0076] The operating pressure of the mixed refrigerant compressor first stage outlet is 0.8-1.5 MPaG, preferably 1.0-1.2 MPaG;

[0077] The operating pressure of the mixed refrigerant compressor second stage is 2.8-4.1 MPaG, preferably 3.1-3.6 MPaG;

[0078] The operating pressure of the mixed refrigerant first liquid separator is 0.8-1.5 MPaG, preferably 1.0-1.2 MPaG;

[0079] The operating pressure of the mixed refrigerant second liquid separator is 2.8-4.1 MPaG, preferably 3.1-3.6 MPaG;

[0080] The overhead temperature of the light component flash tower is -90--125℃, the pressure is 0.08-0.35 MPaG, and the bottom temperature is -90--125℃;

[0081] The overhead temperature of the fractionating tower is -120--140℃, the pressure is 0.45-0.75 MPaG, and the bottom temperature is -120--130℃.

[0082] According to the present application, the mixed refrigerant is selected from at least three of nitrogen, methane, ethylene, ethane, propylene, propane, butane and isopentane.

[0083] The mixed refrigerant is preferably a mixture of nitrogen, methane, ethylene, propane and isopentane, wherein the proportion of nitrogen is 0.6-1.2 mol%, the proportion of methane is 32-45 mol%, the proportion of ethylene is 38-51 mol%, the proportion of propane is 2-5 mol%, and the proportion of isopentane is 9-15 mol% based on the total moles of the mixture.

[0084] The present application will be described in more detail by way of examples.

[0085] Example 1

[0086] The present application provides a device for separating carbon three fraction in propane dehydrogenation to propylene gas phase product, as shown in Figure 1 The device comprises a cold box sequence, a mixed refrigerant refrigerator, a carbon three booster pump P-301, a liquid separator, a light component flash tower C-301 and a fractionating tower C-302.

[0087] The cold box sequence comprises a first stage cold box E-301X, a second stage cold box E-302X, a third stage cold box E-303X and a fourth stage cold box E-304X.

[0088] The liquid separation tank includes a first liquid separation tank D-301, a second liquid separation tank D-302, and a fractionation column C-302;

[0089] The gas phase product feed pipeline is connected with the first-stage cold box E-301X, the second-stage cold box E-302X, the third-stage cold box E-303X, and the first liquid separation tank D-301 in sequence;

[0090] The top of the first liquid separation tank D-301 is connected with the fourth-stage cold box E-304X and the second liquid separation tank D-302 in sequence, and the bottom is connected with the lower inlet of the light component flash tower C-301;

[0091] The top of the second liquid separation tank D-302 is connected with the lower part of the fractionation column C-302, and the bottom is connected with the middle part of the light component flash tower C-301;

[0092] The top of the fractionation column C-302 is connected with the fourth-stage cold box E-304X, and is branched into two branches in sequence, one of which is connected with the third-stage cold box E-303X, the second-stage cold box E-302X, the first-stage cold box E-301X, and the crude hydrogen extraction pipeline, and the other of which is connected with the third-stage cold box E-303X, the second-stage cold box E-302X, the first-stage cold box E-301X, and the reactor feed extraction pipeline, and the bottom is connected with the upper inlet of the light component flash tower C-301;

[0093] The top of the light component flash tower C-301 is provided with a gas phase extraction pipeline, and the bottom is connected with the carbon three booster pump P-301, the third-stage cold box E-303X, the second-stage cold box E-302X, the first-stage cold box E-301X, and the carbon three fraction extraction pipeline in sequence;

[0094] The circulating propane feed pipeline is connected with the first-stage cold box E-301X, the second-stage cold box E-302X, and the third-stage cold box E-303X in sequence, wherein the circulating propane pipeline at the outlet of each stage of the cold box and the reactor feed pipeline at the inlet are connected through an interconnection pipeline, and each of the interconnection pipelines of the first-stage cold box E-301X, the second-stage cold box E-302X, and the third-stage cold box E-303X is provided with a respective mixer and a circulating propane supplement inlet;

[0095] The mixed refrigerant refrigerator includes a mixed refrigerant compressor first stage K-310, a mixed refrigerant first water cooler E-310, a mixed refrigerant first liquid separation tank D-310, a mixed refrigerant compressor second stage K-320, a mixed refrigerant second water cooler E-320, and a mixed refrigerant second liquid separation tank D-320 connected in sequence;

[0096] The bottom of the mixed refrigerant first liquid separation tank D-310 is connected with the mixed refrigerant second liquid separation tank feed pipeline through a mixed refrigerant first booster pump P-310, and the bottom of the mixed refrigerant second liquid separation tank D-320 is connected with the mixed refrigerant discharge pipeline at the top through a mixed refrigerant second booster pump P-320.

[0097] The split condensation fractionating column C-302 is provided with a split condensation fractionating column condenser E-305X;

[0098] The mixed refrigerant refrigerator outlet is connected to the first-stage cold box E-301X, the second-stage cold box E-302X, the third-stage cold box E-303X, the fourth-stage cold box E-304X and the split condensation fractionating column condenser E-305X inlet in sequence; the split condensation fractionating column condenser E-305X outlet is connected to the fourth-stage cold box E-304X, the third-stage cold box E-303X, the second-stage cold box E-303X and the first-stage cold box E-303X, and the mixed refrigerant refrigerator inlet in sequence.

[0099] The main steps of the separation method of the propane dehydrogenation propylene gas phase product in the embodiment are as follows:

[0100] (1) The gas phase product from the deep purification unit is sent into the cold box sequence through the gas phase product feed pipeline, and is cooled to -90°C to -110°C in the first-stage cold box E-301X, the second-stage cold box E-302X and the third-stage cold box E-303X in sequence to obtain a cooled gas phase product;

[0101] (2) The cooled gas phase product is subjected to gas-liquid separation in the first liquid separation tank D-301, the tank bottom liquid phase is sent into the lower part of the light component flash tower C-301, and the tank top gas phase is sent into the fourth-stage cold box E-304X and cooled to -110°C to -130°C to obtain a deep cooling gas phase product;

[0102] (3) The deep cooling gas phase product is sent into the second liquid separation tank D-302 and subjected to gas-liquid separation, the tank bottom liquid phase is sent into the middle part of the light component flash tower C-301, and the tank top gas phase is sent into the lower part of the split condensation fractionating column C-302 and subjected to gas-liquid separation, the liquid phase at the bottom of the column after the gas-liquid separation is sent into the upper part of the light component flash tower C-301, and the gas phase at the top of the column is returned to the fourth-stage cold box E-304X to recover cold energy to obtain a cold energy recovery gas phase;

[0103] (4) The cold energy recovery gas phase is divided into two parts, one part of the gas phase is sequentially subjected to cold energy recovery in the third-stage cold box E-303X, the second-stage cold box E-302X and the first-stage cold box E-301X in sequence to obtain crude hydrogen and is recovered through the crude hydrogen recovery pipeline; the other part of the gas phase is sequentially sent into the third-stage cold box E-303X, the second-stage cold box E-302X and the first-stage cold box E-301X, and is mixed with the countercurrent circulating propane and the supplementary circulating propane added through the supplementary circulating propane inlet in the mixer before entering the cold energy gas inlets of the cold boxes, and the cold energy gas subjected to the cold energy recovery in sequence is recovered through the reactor feed pipeline;

[0104] (5) The light component flash tower C-301 top gas phase is extracted through a gas phase extraction pipeline, and the bottom liquid phase is pressurized by a C3 booster pump P-301 and then sent to a cold box sequence, and cold energy is recovered in a three-stage cold box E-303X, a two-stage cold box E-302X, and a one-stage cold box E-301X to obtain a C3 fraction, which is extracted through a C3 fraction extraction pipeline;

[0105] (6) The mixed refrigerant is pressurized in two stages in a mixed refrigerant refrigerator, cooled by water, and then sent to the cold box sequence through the mixed refrigerant refrigerator outlet, and is sequentially cooled to -123℃ to -143℃ in a one-stage cold box E-301X, a two-stage cold box E-302X, a three-stage cold box E-303X, and a four-stage cold box E-304X, and then returns to the four-stage cold box E-304X, the three-stage cold box E-303X, the two-stage cold box E-302X, and the one-stage cold box E-301X to provide cold energy for the cold box sequence, and then returns to the mixed refrigerant refrigerator inlet.

[0106] In the embodiment, the three-stage cold box E-303X has a circulating propane outlet temperature of -100℃, the circulating propane accounts for 6.9% of the total circulating propane, and the temperature after mixing with the cold energy gas is -106.5℃; the two-stage cold box E-302X has a circulating propane outlet temperature of -50℃, the circulating propane accounts for 16.3% of the total circulating propane, and the temperature after mixing with the cold energy gas is -53.3℃; and the one-stage cold box E-301X has a circulating propane outlet temperature of -25℃, the circulating propane accounts for 76.8% of the total circulating propane, and the temperature after mixing with the cold energy gas is -27.8℃.

[0107] The cold box operation data of Example 1 is shown in Table 1. As can be seen from Table 1, by adding the circulating propane to the circulating propane outlet of each cold box, the cold box shows excellent heat transfer performance, the minimum heat transfer temperature difference at the low temperature end is not less than 3.0℃, the heat transfer temperature difference at the hot end is not less than 3.0℃, and the heat transfer area (UA value) is small.

[0108] Table 1: Cold box operation data of Example 1

[0109] Item Units E-301X E-302X E-303X E-304X Total Minimum temperature difference C 3.00 3.00 3.00 4.74 UA value KCAL / HR-C 8083977 3280986 2394241 207185 13966388

[0110] The power of the mixed refrigerant compressor is 2673kw.

[0111] Example 2

[0112] A separation device for propane dehydrogenation to propylene gas phase product is used as shown in Figure 2 The separation device includes a cold box sequence, a mixed refrigerant refrigerator, a C3 booster pump P-301, a liquid separation tank, a light component flash tower C-301, and a fractional condensation and fractional distillation tower C-302.

[0113] The cold box sequence comprises a first cold box E-301X, a second cold box E-302X, a third cold box E-303X and a fourth cold box E-304X;

[0114] The liquid separation tank comprises a first liquid separation tank D-301 and a second liquid separation tank D-302;

[0115] The gas phase product feed pipeline is connected with the first cold box E-301X, the second cold box E-302X, the third cold box E-303X and the first liquid separation tank D-301 in sequence;

[0116] The top of the first liquid separation tank D-301 is connected with the fourth cold box E-304X and the second liquid separation tank D-302 in sequence, and the bottom is connected with the lower inlet of the light component flash tower C-301;

[0117] The top of the second liquid separation tank D-302 is connected with the lower part of the fractional condensation and fractionation tower C-302, and the bottom is connected with the middle part of the light component flash tower C-301;

[0118] The top of the fractional condensation and fractionation tower C-302 is divided into two branches after being connected with the fourth cold box E-304X, one branch is connected with the third cold box E-303X, the second cold box E-302X, the first cold box E-301X and the crude hydrogen outlet pipeline in sequence, and the other branch is connected with the third cold box E-303X, the second cold box E-302X, the first cold box E-301X and the reactor feed outlet pipeline in sequence, and the bottom is connected with the upper inlet of the light component flash tower C-301;

[0119] The top of the light component flash tower C-301 is provided with a gas phase outlet pipeline, and the bottom is connected with the carbon three booster pump P-301, the third cold box E-303X, the second cold box E-302X, the first cold box E-301X and the carbon three fraction outlet pipeline in sequence;

[0120] The circulating propane feed pipeline is connected with the first cold box E-301X, the second cold box E-302X and the third cold box E-303X in sequence, wherein the circulating propane pipeline at the outlet of the first cold box E-301X and the third cold box E-303X and the reactor feed pipeline at the inlet are connected through an interconnecting pipeline, the interconnecting pipeline of the first cold box E-301X is provided with a first cold box circulating propane supplement inlet B-301 and a first cold box mixer M-301, and the interconnecting pipeline of the third cold box E-303X is provided with a third cold box circulating propane supplement inlet B-303 and a third cold box mixer M-303;

[0121] The mixed refrigerant refrigerator comprises a mixed refrigerant compressor first stage K-310, a mixed refrigerant first water cooler E-310, a mixed refrigerant first liquid separation tank D-310, a mixed refrigerant compressor second stage K-320, a mixed refrigerant second water cooler E-320 and a mixed refrigerant second liquid separation tank D-320 connected in sequence.

[0122] The first mixed refrigerant first knock out drum D-310 is connected to the mixed refrigerant second knock out drum feed line through a first mixed refrigerant booster pump P-310. The first mixed refrigerant second knock out drum D-320 is connected to the mixed refrigerant outlet line at the top of the drum through a second mixed refrigerant booster pump P-320.

[0123] The partial condensation fractionating column C-302 is provided with a partial condensation fractionating column condenser E-305X.

[0124] The mixed refrigerant chiller outlet is connected to the first cold box E-301X, the second cold box E-302X, the third cold box E-303X, the fourth cold box E-304X, and the partial condensation fractionating column condenser E-305X inlet in sequence. The partial condensation fractionating column condenser E-305X outlet is connected to the fourth cold box E-304X, the third cold box E-303X, the second cold box E-303X, and the first cold box E-303X in sequence, and the mixed refrigerant chiller inlet.

[0125] The main steps of the separation method of the propane dehydrogenation to propylene gas phase product in the embodiment are as follows:

[0126] (1) The gas phase product from the deep purification unit is sent into the cold box sequence through the gas phase product feed line, and is cooled to -90℃ to -110℃ in the first cold box E-301X, the second cold box E-302X, and the third cold box E-303X in sequence to obtain a cooled gas phase product;

[0127] (2) The cooled gas phase product is subjected to gas-liquid separation in the first knock out drum D-301, and the liquid phase at the bottom of the drum is sent into the lower part of the light component flash tower C-301, and the gas phase at the top of the drum is sent into the fourth cold box E-304X and cooled to -110℃ to -130℃ to obtain a deep cooling gas phase product;

[0128] (3) The deep cooling gas phase product is sent into the second knock out drum D-302 for gas-liquid separation, and the liquid phase at the bottom of the drum is sent into the middle part of the light component flash tower C-301. The gas phase at the top of the drum is sent into the lower part of the partial condensation fractionating column C-302 for gas-liquid separation. After the gas-liquid separation, the liquid phase at the bottom of the drum is sent into the upper part of the light component flash tower C-301, and the gas phase at the top of the drum is returned to the fourth cold box E-304X to recover the cold energy to obtain a cold energy recovery gas phase;

[0129] (4) The cold recovery gas phase is divided into two parts, one part of the gas phase sequentially passes through the three-stage cold box E-303X, the two-stage cold box E-302X and the one-stage cold box E-301X to sequentially recover cold to obtain crude hydrogen and is recovered through a crude hydrogen recovery pipeline; the other part of the gas phase sequentially enters the three-stage cold box E-303X, the two-stage cold box E-302X and the one-stage cold box E-301X, and before entering the cold gas inlet of the one-stage cold box E-301X and the three-stage cold box E-303X, is mixed with countercurrent circulating propane and supplemental circulating propane added through a circulating propane supplement inlet in a mixer, and the cold gas recovered through the stages is recovered through a reactor feed pipeline;

[0130] (5) The overhead gas phase of the light component flash tower C-301 is recovered through a gas phase recovery pipeline, and the bottom liquid phase is pressurized by a carbon three pressurizing pump P-301 and then sent to the cold box sequence to sequentially recover cold in the three-stage cold box E-303X, the two-stage cold box E-302X and the one-stage cold box E-301X to obtain a carbon three fraction, which is recovered through a carbon three fraction recovery pipeline;

[0131] (6) The mixed refrigerant is pressurized through two stages in a mixed refrigerant refrigerator, cooled by water, and then sent to the cold box sequence through a mixed refrigerant refrigerator outlet, sequentially cooled to -123°C to -143°C in the one-stage cold box E-301X, the two-stage cold box E-302X, the three-stage cold box E-303X and the four-stage cold box E-304X, and returned to the four-stage cold box E-304X, the three-stage cold box E-303X, the two-stage cold box E-302X and the one-stage cold box E-301X to provide cold for the cold box sequence and then returned to the mixed refrigerant refrigerator inlet.

[0132] In the embodiment, the circulating propane outlet temperature of the three-stage cold box E-303X is -100°C, the supplemental circulating propane accounts for 23.2% of the total circulating propane, and the temperature after mixing with the cold gas is -103.6°C; the circulating propane outlet temperature of the two-stage cold box E-302X is -50°C; the circulating propane outlet temperature of the one-stage cold box E-301X is -25°C, the supplemental circulating propane accounts for 76.8% of the total circulating propane, and the temperature after mixing with the cold gas is -27.8°C.

[0133] The cold box operation data of Example 2 is shown in Table 2. As can be seen from Table 2, by adding supplemental circulating propane at the circulating propane outlets of the one-stage cold box E-301X and the three-stage cold box E-303X, the cold box exhibits good heat transfer performance, the minimum heat transfer temperature difference at the low temperature end is not less than 3.0°C, the minimum heat transfer temperature difference at the hot end is not less than 3.0°C, and the heat transfer area (UA value) is small.

[0134] Table 2 Cold box operation data of Example 2

[0135] Item Units E-301X E-302X E-303X E-304X Total Minimum temperature difference C 3.00 3.00 2.99 4.19 UA value KCAL / HR-C 8069702 3242535 3095507 217925 14625669

[0136] The power of the mixed refrigerant compressor is 2966kw.

[0137] Comparative Example 1

[0138] The separation device of the propane dehydrogenation to propylene gas phase product is shown in Figure 3 The separation device includes a cold box sequence, a mixed refrigerant refrigerator, a carbon three booster pump P-301, a liquid separation tank, a light component flash tower C-301, and a partial condensation fractionation tower C-302.

[0139] The cold box sequence includes a first-stage cold box E-301X, a second-stage cold box E-302X, a third-stage cold box E-303X, and a fourth-stage cold box E-304X.

[0140] The liquid separation tank includes a first liquid separation tank D-301, a second liquid separation tank D-302, and a partial condensation fractionation tower C-302.

[0141] The gas phase product feed line is sequentially connected with the first-stage cold box E-301X, the second-stage cold box E-302X, the third-stage cold box E-303X, and the first liquid separation tank D-301.

[0142] The first liquid separation tank D-301 is sequentially connected with the fourth-stage cold box E-304X and the second liquid separation tank D-302 at the top, and is connected with the lower inlet of the light component flash tower C-301 at the bottom.

[0143] The second liquid separation tank D-302 is connected with the partial condensation fractionation tower C-302 at the top, and is connected with the middle of the light component flash tower C-301 at the bottom.

[0144] The partial condensation fractionation tower C-302 is divided into two branches at the top, one branch is sequentially connected with the third-stage cold box E-303X, the second-stage cold box E-302X, the first-stage cold box E-301X, and a crude hydrogen outlet pipeline, the other branch is sequentially connected with the third-stage cold box E-303X, the second-stage cold box E-302X, the first-stage cold box E-301X, and a reactor feed outlet pipeline, and the bottom is connected with the upper inlet of the light component flash tower C-301.

[0145] The light component flash tower C-301 is provided with a gas phase outlet pipeline at the top, and is sequentially connected with the carbon three booster pump P-301, the third-stage cold box E-303X, the second-stage cold box E-302X, the first-stage cold box E-301X, and a carbon three fraction outlet pipeline at the bottom.

[0146] The circulating propane feed pipeline is sequentially connected with the first-stage cold box E-301X, the second-stage cold box E-302X, and the third-stage cold box E-303X, wherein the circulating propane pipeline at the outlet of the third-stage cold box E-303X and the reactor feed pipeline at the inlet are connected through an interconnection pipeline, and a third-stage cold box mixer M-303 is arranged on the interconnection pipeline.

[0147] The mixed refrigerant refrigerator comprises, in sequence, a mixed refrigerant compressor section K-310, a mixed refrigerant first water cooler E-310, a mixed refrigerant first liquid separator D-310, a mixed refrigerant compressor section K-320, a mixed refrigerant second water cooler E-320, and a mixed refrigerant second liquid separator D-320;

[0148] The bottom of the mixed refrigerant first liquid separator D-310 is connected to the mixed refrigerant second liquid separator feed line through a mixed refrigerant first booster pump P-310, and the bottom of the mixed refrigerant second liquid separator D-320 is connected to the mixed refrigerant discharge line at the top through a mixed refrigerant second booster pump P-320;

[0149] The partial condensation and fractionation column C-302 is provided with a partial condensation and fractionation column condenser E-305X;

[0150] The mixed refrigerant refrigerator outlet is connected, in sequence, to the primary cold box E-301X, the secondary cold box E-302X, the tertiary cold box E-303X, the quaternary cold box E-304X, and the partial condensation and fractionation column condenser E-305X inlet; the partial condensation and fractionation column condenser E-305X outlet is connected, in sequence, to the quaternary cold box E-304X, the tertiary cold box E-303X, the secondary cold box E-303X, and the primary cold box E-303X, and the mixed refrigerant refrigerator inlet.

[0151] The main steps of the separation method of the propane dehydrogenation to propylene gas phase product in this comparative example are as follows:

[0152] (1) The gas phase product from the deep purification unit is sent into the cold box sequence through the gas phase product feed line, and is cooled to -90℃ to -110℃ in the primary cold box E-301X, the secondary cold box E-302X, and the tertiary cold box E-303X in sequence to obtain a cooled gas phase product;

[0153] (2) The cooled gas phase product is subjected to gas-liquid separation in the first liquid separator D-301, the liquid phase at the bottom is sent into the lower part of the light component flash tower C-301, and the gas phase at the top is sent into the quaternary cold box E-304X and cooled to -110℃ to -130℃ to obtain a deep cooling gas phase product;

[0154] (3) The deep cooling gas phase product is sent into the second liquid separator D-302 for gas-liquid separation, the liquid phase at the bottom is sent into the middle part of the light component flash tower C-301, and the gas phase at the top is sent into the lower part of the partial condensation and fractionation column C-302 for gas-liquid separation, and the liquid phase at the bottom after the gas-liquid separation is sent into the upper part of the light component flash tower C-301, and the gas phase at the top is returned to the quaternary cold box E-304X after recovering the cold energy to obtain a cold energy recovery gas phase;

[0155] (4) The cold recovery gas phase is divided into two parts, one part of the gas phase sequentially passes through the three-stage cold box E-303X, the two-stage cold box E-302X and the one-stage cold box E-301X to sequentially recover cold and obtain crude hydrogen, and is recovered through a crude hydrogen recovery pipeline; the other part of the gas phase sequentially enters the three-stage cold box E-303X, the two-stage cold box E-302X and the one-stage cold box E-301X, and is mixed with the countercurrent circulating propane in the three-stage cold box mixer M-303 before entering the cold gas inlet of the three-stage cold box E-303X, and the cold gas recovered by the three-stage cold recovery is recovered through a reactor feed pipeline;

[0156] (5) The light component flash tower C-301 overhead gas phase is recovered through a gas phase recovery pipeline, and the bottom liquid phase is pressurized by a carbon three booster pump P-301 and sent to the cold box sequence, and is sequentially recovered by the three-stage cold box E-303X, the two-stage cold box E-302X and the one-stage cold box E-301X to obtain a carbon three fraction, and the carbon three fraction is recovered through a carbon three fraction recovery pipeline;

[0157] (6) The mixed refrigerant is pressurized by two stages in the mixed refrigerant refrigerator, cooled by water, and then sent to the cold box sequence through the mixed refrigerant refrigerator outlet, and is sequentially cooled to -123℃ to -143℃ in the one-stage cold box E-301X, the two-stage cold box E-302X, the three-stage cold box E-303X and the four-stage cold box E-304X, and is returned to the four-stage cold box E-304X, the three-stage cold box E-303X, the two-stage cold box E-302X and the one-stage cold box E-301X after providing cold to the condenser E-305X of the fractional condensation and fractional distillation tower, and is returned to the mixed refrigerant refrigerator inlet after providing cold to the cold box sequence.

[0158] In the comparative example, the circulating propane outlet temperature of the three-stage cold box E-303X is -100℃, and all the circulating propane is mixed with the cold gas and supplemented into the cold box, and the cold box temperature is -103℃

[0159] The cold box operation data of the comparative example 1 is shown in Table 3. As can be seen from Table 3, the heat transfer of the cold box of the comparative example 1 is poor, and the cold box operation data of the comparative example 1 is shown in Table 3. The cold box heat transfer area is very large, and the UA value of the comparative example 1 is only 83.7% and 87.6% of the comparative example 1.

[0160] Table 3 Cold box operation data of comparative example 1

[0161] Item Units E-301X E-302X E-303X E-304X Total Minimum temperature difference C 3.00 2.99 3.00 3.67 UA value KCAL / HR-C 7943324 4235696 4283609 223778 16686406

[0162] The mixed refrigerant compressor power is 3701kw.

[0163] In summary, the propane dehydrogenation to propylene gas phase product separation device and separation method of Example 1 and Example 2 have very significant effects, which can reduce the cooling temperature of the carbon three stream, reduce the heat exchange area of the heat exchanger, at the same time, the cold energy utilization of Example 1 and Example 2 is more reasonable, the thermodynamic efficiency is higher, and the energy consumption is lower.

[0164] The above has described various embodiments of the present application, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes are obvious to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A device for separating carbon trimers from a propane dehydrogenation to propylene gas phase product, characterized in that, The device comprises a cold box sequence, a carbon three booster pump, a liquid separation tank, a light component flash tower, and a fractionating tower. The cold box sequence comprises a first cold box, a second cold box, a third cold box, and a fourth cold box. The liquid separation tank comprises a first liquid separation tank and a second liquid separation tank. The gaseous phase product feed pipeline is connected to the first cold box, the second cold box, the third cold box, and the first liquid separation tank in sequence. The first liquid separation tank top is connected to the fourth cold box and the second liquid separation tank in sequence. The second liquid separation tank bottom is connected to the middle part of the light component flash tower. The fractionating tower top is connected to the fourth cold box, and is branched into two branches in sequence. One branch is connected to the third cold box, the second cold box, the first cold box, and a crude hydrogen extraction pipeline in sequence. The other branch is connected to the third cold box, the second cold box, the first cold box, and a reactor feed extraction pipeline in sequence.

2. The apparatus of claim 1, wherein, The light component flash tower top is provided with a gaseous phase extraction pipeline. The light component flash tower bottom is connected to the carbon three booster pump, the third cold box, the second cold box, the first cold box, and a carbon three fraction extraction pipeline in sequence. The circulating propane feed pipeline is connected to the first cold box, the second cold box, and the third cold box in sequence. At least two circulating propane pipelines at the outlets of the cold boxes and the reactor feed pipelines at the inlets are connected through interconnecting pipelines. Each interconnecting pipeline is provided with a mixer and a circulating propane supplement inlet.

3. The apparatus of any of claims 1-2, wherein, The device further comprises a mixed refrigerant refrigerator.

4. A process for separating the carbon trimmer fraction from the propane dehydrogenation to propylene gas phase product using the apparatus of any one of claims 1 to 3, characterized in that, The mixed refrigerant refrigerator comprises a mixed refrigerant compressor first stage, a mixed refrigerant first water cooler, a mixed refrigerant first liquid separation tank, a mixed refrigerant compressor second stage, a mixed refrigerant second water cooler, and a mixed refrigerant second liquid separation tank connected in sequence. (1) The gaseous products from the deep purification unit are fed into the cold box sequence through the gaseous product feed pipeline, and cooled to -90°C in the first-stage cold box, second-stage cold box, and third-stage cold box. o C~-110 o C yields cooled gaseous products; (2) The cooled gas phase product is subjected to gas-liquid separation in a first knock-out drum, the bottom liquid phase is sent to the lower part of the light component flash tower, and the top gas phase is sent to the fourth level cold box and cooled to -110 o C~ -130 o C to obtain a cryogenic gas phase product; The mixed refrigerant first liquid separation tank bottom is connected to the mixed refrigerant second liquid separation tank feed pipeline through a mixed refrigerant first booster pump. The mixed refrigerant second liquid separation tank bottom is connected to the mixed refrigerant outlet pipeline at the tank top through a mixed refrigerant second booster pump. The fractionating tower is provided with a fractionating tower condenser. The mixed refrigerant refrigerator is connected to the first cold box, the second cold box, the third cold box, the fourth cold box, and the fractionating tower condenser inlet in sequence. The fractionating tower condenser outlet is connected to the fourth cold box, the third cold box, the second cold box, the first cold box, and the mixed refrigerant refrigerator inlet in sequence. Each interconnecting pipeline is provided with at least one circulating propane supplement inlet and one mixer. The circulating propane supplement inlets and the mixers are independently controlled. The liquid separation tank bottom is provided with a flow control valve. The method comprises the following steps: (3) The cryogenic gaseous phase product is sent into the second liquid separation tank for gas-liquid separation. The liquid phase at the tank bottom is sent into the middle part of the light component flash tower. The gaseous phase at the tank top is sent into the lower part of the fractionating tower for gas-liquid separation. The liquid phase at the fractionating tower bottom is sent into the upper part of the light component flash tower. The gaseous phase at the fractionating tower top is returned to the fourth cold box for cold energy recovery to obtain a cold energy recovery gaseous phase. (4) the cold energy recovery gas phase is divided into two parts, one part of the gas phase sequentially passes through the three-stage cold box, the two-stage cold box and the one-stage cold box to recover cold energy step by step to obtain crude hydrogen and is recovered through a crude hydrogen recovery pipeline; the other part of the gas phase sequentially enters the three-stage cold box, the two-stage cold box and the one-stage cold box, and before entering the inlet of each cold box, is mixed with countercurrent circulating propane in a mixer, or is mixed with countercurrent circulating propane and supplemental circulating propane added through a circulating propane supplement inlet in the mixer, and cold energy gas recovered through the cold energy recovery step by step is recovered through a reactor feed pipeline; (5) the light component flash tower overhead gas phase is recovered through a gas phase recovery pipeline, and the bottom liquid phase is pressurized by a C3 booster pump and then sent to the cold box sequence to recover cold energy step by step in the three-stage cold box, the two-stage cold box and the one-stage cold box to obtain a C3 fraction, and the C3 fraction is recovered through a C3 fraction recovery pipeline.

5. The method of claim 4, wherein, The method further comprises: (6) The mixed refrigerant is sent into the cold box sequence through the mixed refrigerant refrigerator outlet after two-stage pressurization and water cooling, and is cooled to -123 o C~-143 o C pressure reduction, provides cold energy for the condenser of the fractional condensation fractionating tower, and then returns to the fourth-stage cold box, the third-stage cold box, the second-stage cold box, and the first-stage cold box to provide cold energy for the cold box sequence and returns to the mixed refrigerant refrigerator inlet. The number of the circulating propane supplement inlets is not less than 2.

6. The method according to any of claims 4-5, characterized by, Supplemental circulating propane is added to the three-stage cold box, the two-stage cold box and the one-stage cold box; The temperature of the supplemental circulating propane added by the third cold box is -110 o C ~ -90 o C, 0 ~ 20% of the total circulating propane The temperature of the supplementary circulating propane added into the secondary cold box is -90 o C~ -40 o C, 10%~25% of the total circulating propane The temperature of the supplemental circulating propane added to the primary cold box is -60 o C~0 o C, accounting for 65%~87% of the total circulating propane.

7. The method of any of claims 4-5, wherein, The supplemental circulating propane added to the three-stage cold box accounts for 5% to 12% of the total circulating propane amount; The supplemental circulating propane added to the two-stage cold box accounts for 12% to 18% of the total circulating propane amount; The supplemental circulating propane added to the one-stage cold box accounts for 70% to 83% of the total circulating propane amount.

8. The method of any of claims 4-5, wherein, Supplemental circulating propane is added to the three-stage cold box and the one-stage cold box; The temperature of the supplemental circulating propane added into the third cold box is -110 o C ~ -90 o C, 5~50% of the total circulating propane The temperature of the supplemental circulating propane added to the primary cold box is -90 o C0 o C, 50%~95% of the total circulating propane.

9. The method of any of claims 4-5, wherein, The supplemental circulating propane added to the three-stage cold box accounts for 15% to 40% of the total circulating propane amount; The supplemental circulating propane added to the one-stage cold box accounts for 60% to 85% of the total circulating propane amount.

10. The method of any of claims 4-5, wherein, The mass ratio of the supplemental circulating propane to the mass of the C3 fraction condensed from the gas phase product is 0.5 to 2:

1.

11. The method of any of claims 4-5, wherein, The mass ratio of the supplemental circulating propane to the mass of the C3 fraction condensed from the gas phase product is 0.8 to 1.35:

1.

12. The method according to any one of claims 4-5, wherein: the mixed refrigerant refrigerator inlet operating pressure is 0.15-0.32 MPaG; and the mixed refrigerant refrigerator outlet operating pressure is 2.8-4.1 MPaG; the C3 booster pump operating temperature is -90--115℃, and the operating pressure is 1.7-4.3 MPaG; the mixed refrigerant first booster pump operating pressure is 2.8-4.1 MPaG; the mixed refrigerant second booster pump operating pressure is 2.9-4.3 MPaG; the mixed refrigerant compressor first stage operating pressure is 0.8-1.5 MPaG; the mixed refrigerant compressor second stage operating pressure is 2.8-4.1 MPaG; the mixed refrigerant first liquid separator operating pressure is 0.8-1.5 MPaG; the mixed refrigerant second liquid separator operating pressure is 2.8-4.1 MPaG; the light component flash tower overhead temperature is -90--125℃, and the pressure is -0.08-0.35 MPaG; and the bottom temperature is -90--125℃; the partial condensation fractional distillation column overhead temperature is -120--140℃, and the pressure is 0.45-0.75 MPaG; and the bottom temperature is -120--130℃.

13. The method according to any one of claims 4-5, wherein: The mixed refrigerant refrigeration machine inlet operating pressure is 0.19-0.28 MPaG; the mixed refrigerant refrigeration machine outlet operating pressure is 3.1-3.7 MPaG; The mixed refrigerant first booster pump operating pressure is 3.1-3.6 MPaG; The mixed refrigerant second booster pump operating pressure is 3.6-3.9 MPaG; The mixed refrigerant compressor first stage operating pressure is 1.0-1.2 MPaG; The mixed refrigerant compressor second stage operating pressure is 3.1-3.6 MPaG; The mixed refrigerant first liquid separator operating pressure is 1.0-1.2 MPaG; The mixed refrigerant second liquid separator operating pressure is 3.1-3.6 MPaG.

14. The method of any of claims 4-5, wherein, The mixed refrigerant is selected from at least three of nitrogen, methane, ethylene, ethane, propylene, propane, butane, and isopentane.

15. The method of any of claims 4-5, wherein, The mixed refrigerant is a mixture of nitrogen, methane, ethylene, propane, and isopentane, wherein the nitrogen accounts for 0.6-1.2 mol%, the methane accounts for 32-45 mol%, the ethylene accounts for 38-51 mol%, the propane accounts for 2-5 mol%, and the isopentane accounts for 9-15 mol% based on the total moles of the mixture.

Images