Propylene oxide purification device, method for producing purified propylene oxide, and method for restarting propylene oxide purification device

Abstract

This propylene oxide purification device is provided with a line LX and / or a line LY. The line LX is configured so as to supply a liquid in a first drum D10 to a first distillation column T10 via a feed inlet 10i of the first distillation column T10, and the line LY is configured so as to supply a liquid in a third drum D30 to the first distillation column T10 via the feed inlet 10i of the first distillation column T10.

Description

Propylene oxide purification apparatus, method for producing purified propylene oxide, and method for restarting a propylene oxide purification apparatus

[0001] The present invention relates to a propylene oxide purification apparatus, a method for producing purified propylene oxide, and a method for restarting a propylene oxide purification apparatus.

[0002] Conventionally, there have been known apparatuses for purifying crude propylene oxide. For example, Patent Publication 1 discloses a purification apparatus using four distillation columns.

[0003] In the first distillation column, crude propylene oxide is distilled, and high-boiling components having a boiling point higher than that of propylene oxide are discharged from the bottom, and a propylene oxide-containing stream from which the high-boiling components have been removed is discharged from the top. In the second distillation column, the overhead stream from the first distillation column is distilled together with the extractant, and water is discharged from the top, and a mixture of the extractant and propylene oxide from which the water has been removed is discharged from the bottom. In the third distillation column, a mixture of the extractant and propylene oxide is distilled, and the extractant is discharged from the bottom, and purified propylene oxide is discharged from the top. In the fourth distillation column, the extractant discharged from the bottom of the third distillation column is distilled, and the purified extractant is recycled to the second distillation column.

[0004] Chinese Patent Publication No. 104109138

[0005] If any malfunction occurs in the apparatus for purifying crude propylene oxide, the purity of the propylene oxide-containing composition discharged from the top of the third distillation column may not be sufficiently high, and a propylene oxide-containing liquid having a purity lower than expected may accumulate in various drums within the apparatus.

[0006] In such a case, even if the propylene oxide-containing liquid having a purity lower than expected stored in each drum is transferred to the downstream stage of the purification device for purification treatment, the conditions of the distillation column must be constantly monitored and the operating conditions must be adjusted appropriately, which requires skilled operating techniques.

[0007] Therefore, conventionally, the propylene oxide-containing composition in each drum has often been discarded.

[0008] A first object of the present invention is to provide a propylene oxide purification apparatus that can increase the product yield even when a malfunction occurs during operation.

[0009] Furthermore, in conventional apparatuses, when the apparatus is started up, it may take a long time before the apparatus is able to steadily produce high-purity propylene oxide.

[0010] A second object of the present invention is to provide a method for restarting a propylene oxide purification apparatus that can shorten the start-up time.

[0011] [1] A first distillation column (T10) having a feed inlet (10i) connected to a supply source (S1) of a stream containing propylene oxide via a line LG, a column top outlet (10t) or a side cut outlet (10s), and a column bottom outlet (10b); either a first liquefaction means (C10) for liquefying a stream discharged from the column top outlet (10t) of the first distillation column (T10) or a first side cut line (LA) connected to the side cut outlet (10s) of the first distillation column; a first drum (D10) for storing a liquid supplied from the first liquefaction means (C10) or the first side cut line (LA); a third distillation column (T30) having a feed inlet (30i) connected to the first drum (D10) via a line LL, a column top outlet (30t) or a side cut outlet (30s), and a column bottom outlet (30b); a third drum (D30) for storing the liquid discharged from the third liquefaction means (C30) or the third side cut line (L7) connected to the side cut outlet (30s) of the third distillation column (T30); a third drum (D30) for storing the liquid discharged from the third liquefaction means (C30) or the third side cut line (L7); and at least one of a line LX and a line LY, wherein the line LX is configured to supply the liquid in the first drum (D10) to the first distillation column (T10) via the feed inlet (10i) of the first distillation column (T10), and the line LY is configured to supply the liquid in the third drum (D30) to the first distillation column (T10) via the feed inlet (10i) of the first distillation column (T10). 1, FIG. 5 (side cut), FIG. 6 (side cut), etc.

[0012] [2] The apparatus according to [1], further comprising a product drum (D200) connected to the third drum (D30), wherein the line LY connects the feed inlet (10i) of the first distillation column (T10) to the third drum (D30) via the product drum (D200). This may correspond to LY2 (L22 + L8) in Figure 1, and may correspond to returning the product via the product drum D200 as a subordinate concept of LY.

[0013] [3] The apparatus according to [1] or [2], wherein the line LL is provided with a second distillation column (T20) having a feed inlet (20i) connected to the first drum (D10) of the first distillation column (T10), a column top outlet (20t), and a column bottom outlet (20b) connected to the feed inlet (30i) of the third distillation column (T30), and the apparatus further comprises a line for directly or indirectly supplying an extractant into the second distillation column (T20).

[0014] [4] The apparatus according to [3], further comprising: a liquefaction separation facility LQ that liquefies at least a portion of a stream supplied from a top outlet (20t) or a side cut outlet of the second distillation column (T20) via a line LB, and discharges the gas phase from a gas phase outlet (LQg) and the liquid phase from a liquid phase outlet (LQl); and a line LC that connects the liquid phase outlet (LQl) of the liquefaction separation facility LQ with a reflux inlet (20r) of the second distillation column (T20).

[0015] [5] The apparatus according to [4], wherein the liquefaction separation facility LQ has a gas-liquid separator (22) including the gas phase outlet (LQg), the liquid phase outlet (LQl), and a fluid inlet connected to the top outlet of the second distillation column (T20) by the line LB. This is a specific example of the liquefaction separation facility LQ and may correspond to FIG. 2 for gas-liquid separation.

[0016] [6] The apparatus according to [4], wherein the liquefaction separation facility LQ has a three-phase separator (23) including the gas phase outlet (LQg), the liquid phase outlet (LQl), an aqueous phase outlet (23w), and a fluid inlet (23i) connected to the top outlet of the second distillation column (T20) by the line LB, and the apparatus further includes a line for directly or indirectly supplying water into the three-phase separator (23). This is a specific example of the liquefaction separation facility LQ and may correspond to the three-phase separator shown in FIG. 9.

[0017] [7] The apparatus according to [4], wherein the liquefaction separation facility LQ comprises a liquefaction means (C26) connected to a top outlet of the second distillation column (T20) via a line LB, and a fifth distillation column (T50) including a feed inlet (50i) connected to the liquefaction means (C26), the vapor phase outlet (LQg) provided at the top of the column, and the liquid phase outlet (LQl) provided at the bottom of the column. This is a specific example of the liquefaction separation facility LQ and can correspond to the distillation column shown in Figure 10.

[0018] [8] The apparatus according to any one of [1] to [7], wherein the line LX connects the first drum (D10) and the line LG, and the line LY connects the third drum (D30) and the line LG. This may correspond to Figure 1.

[0019] [9] A system further comprising: a first-stage second distillation column (T120) having a feed inlet (120i), a top outlet (120t), and a bottom outlet (120b) connected to a supply source (S2) of a stream containing propylene oxide and alcohol and / or water derived from a peroxide; a first-stage second liquefaction means (C120) for liquefying a stream discharged from the top outlet (120t) of the first-stage second distillation column (T120); and a first-stage second drum (D120) for storing a liquid discharged from the first-stage second liquefaction means (C120), wherein the supply source (S1) of the stream containing propylene oxide is the first drum (D120), and the line LX connects the first drum (D10) and the first drum (D120), The apparatus according to any one of [1] to [8], wherein the line LY connects the third drum (D30) and the second drum (D120) for the preceding process.

[0020]

[10] The device according to any one of [1] to [9], further comprising an intermediate drum (D130) provided on the line LG, wherein the line LX connects the first drum (D10) and the intermediate drum (D130), and the line LY connects the third drum (D30) and the intermediate drum (D130). This may correspond to Figures 4 to 8.

[0021]

[11] The apparatus according to

[10] , further comprising: a first-stage second distillation column (T120) having a feed inlet (120i), a top outlet (120t), and a bottom outlet (120b) connected to a supply source (S2) of a stream containing propylene oxide and alcohol and / or water derived from a peroxide; a first-stage second liquefaction means (C120) for liquefying the stream discharged from the top outlet (120t) of the first-stage second distillation column (T120); and a first-stage second drum (D120) for storing the liquid discharged from the first-stage second liquefaction means (C120), wherein the supply source (S1) of the stream containing propylene oxide is the first-stage second drum (D120) of the first-stage second distillation column (T120). This may correspond to Figures 4 to 8.

[0022]

[12] The apparatus according to any one of [1] to

[11] , wherein a line LG connecting the feed inlet (10i) of the first distillation column (T10) and the supply source (S1) of a stream containing propylene oxide is provided with a sixth distillation column (auxiliary distillation column) (T60) or a seventh distillation column (auxiliary distillation column) (T70) for distilling the stream fed from the supply source (S1). This may correspond to Figures 7 and 8 for the four columns.

[0023]

[13] A method for producing purified propylene oxide using the propylene oxide purification apparatus according to any one of [1] to

[12] , comprising a step of returning the propylene oxide-containing liquid stored in at least one of the first drum (D10) and the third drum (D30) to the first distillation column (T10) via at least one of the line LX and the line LY when the purity of the propylene oxide-containing liquid stored in at least one of the first drum (D10) and the third drum (D30) falls below a predetermined threshold.

[0024]

[14] An epoxidation reactor that reacts peroxide with propylene to produce a first mixture stream containing propylene oxide, and a peroxide-derived alcohol and / or water; a first upstream distillation column (T110) having a feed inlet (110i) to which the first mixture stream is supplied, either a top outlet (110t) or a side cut outlet for discharging a stream containing unreacted propylene, and a bottom outlet (110b) for discharging a stream containing propylene oxide, and a peroxide-derived alcohol and / or water; a second upstream distillation column (T120) having a feed inlet (120i) to which a stream discharged from the bottom outlet (110b) of the first upstream distillation column (T110) is supplied, a bottom outlet (120b) for discharging a stream containing peroxide-derived alcohol and / or water, and either a top outlet (120t) or a side cut outlet for discharging a stream containing propylene oxide; either a upstream second liquefaction means (C120) that liquefies the stream discharged from the top outlet of the upstream second distillation column or a upstream second side cut line connected to the side cut outlet of the upstream second distillation column; a upstream second drum (D120) that stores the liquid discharged from the upstream second liquefaction means (C120) or the upstream second side cut line; a first distillation column (T10) having a feed inlet (10i) connected to the upstream second drum (D120), either a top outlet (10t) or a side cut outlet from which propylene oxide and light components are discharged, and a bottom outlet (10b) from which heavy components are discharged; either a first liquefaction means (C10) that liquefies the stream discharged from the top outlet of the first distillation column or a first side cut line connected to the side cut outlet of the first distillation column; a first drum (D10) that stores the liquid discharged from the first liquefaction means (C10) or the first side cut line; a second distillation column (T20) having a feed inlet (20i) connected to the first drum (D10), a top outlet (20t) or a side cut outlet for discharging light components and the extractant, and a bottom outlet (20b) for discharging a stream containing propylene oxide and the extractant;A method for restarting a propylene oxide purification apparatus, comprising: a third distillation column (T30) having a feed inlet (30i) to which a stream containing propylene oxide and an extractant is supplied from a bottom outlet (20b) of the second distillation column (T20), either a top outlet (30t) or a side cut outlet for discharging the stream containing propylene oxide, and a bottom outlet (30b) for discharging the extractant; either a third liquefaction means (C30) for liquefying the stream discharged from the top outlet of the third distillation column (T30) or a third side cut line (L7) connected to the side cut outlet of the third distillation column (T30); and a third drum (D30) for storing a liquid discharged from the third liquefaction means (C30) or the third side cut line (L7), a step O of storing at least one of the streams containing propylene oxide in the preceding step second drum (D120), the first drum (D10), and the third drum (D30) in at least one of the preceding step second drum (D120), the first drum (D10), and the third drum (D30) and / or in a drum other than the three drums of the preceding step second drum (D120), the first drum (D10), and the third drum (D30) during shutdown of the propylene oxide purification apparatus; a step P of supplying the stream containing propylene oxide stored in the step O to a feed inlet (110i) of the preceding step first distillation column (T110) and operating the preceding step first distillation column (T110) and the preceding step second distillation column (T120); a step Q of supplying the stream containing propylene oxide stored in the step O to the feed inlet (10i) of the first distillation column (T10) and supplying an extractant to the second distillation column (T20) to operate the first distillation column (T10), the second distillation column (T20), and the third distillation column (T30); an R step after the start of the steps P and Q of initiating a reaction between peroxide and propylene in the epoxidation reactor to produce a first mixture stream containing propylene oxide and alcohol and / or water derived from the peroxide, and supplying the first mixture stream to the feed inlet (110i) of the previous step first distillation column (T110) and supplying a stream in the previous step second drum (D120) to the feed inlet (10i) of the first distillation column (T10);A method for restarting a propylene oxide purification plant, which may correspond to FIG.

[0025]

[15] The method according to

[14] , wherein in the step O, at least one of the streams containing propylene oxide is stored in an intermediate drum (D130) provided between the upstream second drum (D120) and the feed inlet (10i) of the first distillation column (T10) and / or a product drum (D200) connected to the third drum (D30).

[16] The step Q further includes a step Q1 in which the stream accumulated in the first drum (D10) of the first distillation column (T10) is refluxed to the first distillation column (T10) without being sent to the second distillation column (T20), and an extractant is circulated between the second distillation column (T20) and the third distillation column (T30); a step Q2 in which, after the step Q1, the stream accumulated in the first drum (D10) of the first distillation column (T10) is supplied to the third distillation column (T30) without passing through the second distillation column (T20), and distilled in the third distillation column (T30), and a stream from the top outlet (30t) or the side cut outlet of the third distillation column (T30) is refluxed from the third drum (D30) to the third distillation column (T30); and The method according to

[14] or

[15] , further comprising a step Q3 of supplying the stream from the first drum (D10) of the first distillation column (T10) to a feed inlet (20i) of the second distillation column (T20) after the step Q2. This may be relevant to an embodiment in which the propylene oxide purification system T10 to T30 are divided into systems.

[0026]

[17] The method according to

[16] , wherein in the step Q2, the stream stored in the first drum (D10) of the first distillation column (T10) is supplied to the third distillation column (T30) via a line without passing through the second distillation column (T20).

[0027]

[18] The method according to

[16] , wherein in the step Q2, the stream stored in the first drum (D10) of the first distillation column (T10) is supplied to the third drum (D30) of the third distillation column (T30) without passing through the second distillation column (T20).

[0028]

[19] The method according to

[16] , wherein the apparatus further comprises: a fourth distillation column (T40) having a feed inlet (40i) connected to the bottom outlet (30b) of the third distillation column (T30), a top outlet (40t), and a bottom outlet (40b); a fourth liquefaction means (C40) for liquefying a stream discharged from the top outlet (40t) of the fourth distillation column (T40); and a fourth drum (D40) for storing a liquid discharged from the fourth liquefaction means (C40), and further wherein the step Q comprises the steps of supplying at least a portion of a stream containing the extractant discharged from the bottom outlet of the third distillation column (T30) to the fourth distillation column (T40), and totally refluxing the stream from the fourth drum (D40) to the fourth distillation column (T40).

[0029]

[20] Further provided between the first distillation column (T10) and the upstream second drum (D120) is another distillation column (T60 or T70) having a feed inlet (60i or 70i) connected to the upstream second drum (D120), a column top outlet (60t or 70t) connected to the auxiliary drum (D60 or D70) via a liquefaction means (C60 or C70), a reflux inlet (60r or 70r) connected to the auxiliary drum (D60 or D70), and a column bottom outlet (60b or 70b), wherein the auxiliary drum (D60) or the column bottom outlet (70b) is connected to the feed inlet 10i of the first distillation column (T10), The method according to

[14] or

[15] , wherein in the step Q, the stream containing propylene oxide stored in the step O is supplied to the other distillation column (T60 or T70), and then supplied to the first distillation column (T10) via the auxiliary drum (D60) or the column bottom outlet (70b). This method corresponds to the restart method in the cases of Figures 7 and 8.

[0030]

[21] The method according to

[20] , wherein in the step O, at least one of the streams containing propylene oxide is stored in an intermediate drum (D130) provided between the second drum (D120) in the preceding step and the feed inlet of the other distillation column (T60 or T70) and / or a product drum (D200) connected to the third drum (D30). This can correspond to the restart method in the cases of Figures 7 and 8.

[0031] According to the first aspect of the present invention, there is provided a propylene oxide purification apparatus that can increase the product yield even when an operational malfunction occurs.

[0032] According to a second aspect of the present invention, there is provided a method for restarting a propylene oxide refinery apparatus, which is capable of shortening the start-up time.

[0033] FIG. 1 is a flow diagram of a propylene oxide purification system according to a first embodiment of the present invention. FIG. 2 is a flow diagram showing an example of a liquefaction separation facility LQ of the present invention. FIG. 3 is a flow diagram of a propylene oxide purification system according to a second embodiment of the present invention. FIG. 4 is a flow diagram of a propylene oxide purification system according to a third embodiment of the present invention. FIG. 5 is a flow diagram of a propylene oxide purification system according to a fourth embodiment of the present invention. FIG. 6 is a flow diagram of a propylene oxide purification system according to a fifth embodiment of the present invention. FIG. 7 is a flow diagram of a propylene oxide purification system according to a sixth embodiment of the present invention. FIG. 8 is a flow diagram of a propylene oxide purification system according to a seventh embodiment of the present invention. FIG. 9 is a flow diagram showing another example of a liquefaction separation facility LQ of the present invention. FIG. 10 is a flow diagram showing another example of a liquefaction separation facility LQ of the present invention.

[0034] First Embodiment A propylene oxide purification apparatus 100 according to a first embodiment will be described with reference to FIG.

[0035] This propylene oxide purification system 100 mainly comprises a first distillation column T10, a second distillation column T20, a liquefaction separation facility LQ, and a third distillation column T30.

[0036] (First Distillation Column and Its Surroundings) The first distillation column T10 has a feed inlet 10i for receiving crude propylene oxide from a upstream second drum D120 as a supply source S1 of a propylene oxide-containing stream described below, a reflux inlet 10r, a column bottom outlet 10b, and a column top outlet 10t. The feed inlet 10i and the supply source S1 of crude propylene oxide are connected by a line LG.

[0037] A top outlet 10t of the first distillation column T10 is connected to a first drum D10 by a line LA. The line LA is provided with a first liquefaction means C10 that liquefies the stream discharged from the top outlet 10t of the first distillation column T10, and the liquid discharged from the first liquefaction means C10 is stored in the first drum D10. The first liquefaction means C10 may be, for example, a heat exchanger to which a refrigerant is supplied.

[0038] The first drum D10 is connected to a feed inlet 20i of the second distillation column T20 via a line LF. The first drum D10 is connected to a reflux inlet 10r of the first distillation column T10 via a line L3. The reflux inlet 10r is located above the feed inlet 10i. A line LI for discharging heavy components is provided at the bottom outlet 10b of the first distillation column T10.

[0039] (Second distillation column T20 and its surroundings) The second distillation column T20 has a feed inlet 20i, a reflux inlet 20r, a bottom outlet 20b, and a top outlet 20t. The first drum D10 and the feed inlet 20i of the second distillation column T20 are connected by a line LF. The bottom outlet 20b of the second distillation column T20 and the feed inlet 30i of the third distillation column T30 are connected by a line LD. The line LA, the first liquefaction means C10, the first drum D10, the line LF, the second distillation column T20, and the line LD constitute a line connecting the top outlet 10t of the first distillation column T10 and the feed inlet 30i of the third distillation column T30. The line LF, the second distillation column T20, and the line LD constitute a line LL connecting the first drum D10 and the feed inlet 30i of the third distillation column T30. The top outlet 20t of the second distillation column T20 is connected to the inlet LQi of the liquefaction separation facility LQ.

[0040] (Liquefaction separation equipment LQ) The liquefaction separation equipment LQ is equipped with an inlet LQi, a gas phase outlet LQg, and a liquid phase outlet LQl. A gas phase stream supplied from the top outlet 20t of the second distillation column T20 is supplied to the inlet LQi via a line LB. The liquefaction separation equipment LQ liquefies at least a portion of the supplied gas phase stream, and discharges the gas phase from the gas phase outlet LQg and the liquid phase from the liquid phase outlet LQl. The liquid phase outlet LQl is connected to a reflux inlet 20r of the second distillation column T20 via a line LC.

[0041] (Example of Liquefaction Separation Facility LQ) An example of the liquefaction separation facility LQ in this embodiment will be described with reference to Fig. 2. Fig. 2 is a diagram showing the connection relationship between the liquefaction separation facility LQ and nearby facilities.

[0042] The liquefaction separation facility LQ includes a cooler (liquefaction unit) 26, a line LQ1, a gas-liquid separator 22, and a connection unit (liquefaction unit) LBJ1.

[0043] A line LB connects the top outlet 20t of the second distillation column T20 to the inlet 26i of the cooler 26 (the inlet LQi of the liquefaction separation facility LQ).

[0044] The line LQ1 connects the outlet 26 o of the cooler 26 and the fluid inlet 22 i of the gas-liquid separator 22 .

[0045] The gas-liquid separator 22 has a fluid inlet 22i, a gas phase outlet 22g (gas phase outlet LQg of the liquefaction separation facility LQ), and a liquid phase (oil phase) outlet 22o (liquid phase outlet LQl of the liquefaction separation facility LQ). The connection part LBJ1 is a junction of the line LQ1 and a line LE described later.

[0046] The cooler 26 and the connection part LBJ1 liquefy at least a portion of the stream supplied via line LB from the top outlet 20t of the second distillation column T20 by changing the phase from gas to liquid through cooling and by contact with the liquid, respectively. The gas-liquid separator 22 separates the fluid containing liquid and gas supplied from the fluid inlet 22i into gas and liquid, and discharges the gas phase from a gas-phase outlet 22g and the liquid phase from a liquid-phase outlet (oil-phase outlet) 22o.

[0047] The cooler 26 can be a heat exchanger to which a refrigerant is supplied. The shape of the heat exchanger is not particularly limited, and examples thereof include a shell-and-tube heat exchanger and a plate-type heat exchanger. An example of an operating condition of the cooler 26 is to cool the stream flowing through the cooler 26 so that the outlet temperature is equal to or lower than the boiling point of propylene oxide, or so that at least a liquid phase is produced at the outlet of the stream.

[0048] The gas-liquid separator 22 may have a variety of configurations as long as it can store a fluid containing a liquid and a gas, form a gas-liquid interface, separate the gas phase above the gas-liquid interface and the liquid phase below the gas-liquid interface, and independently discharge the gas phase from a gas-phase outlet and the liquid phase from a liquid-phase outlet. Typically, the liquid phase outlet 22o is provided at the bottom of the drum-shaped gas-liquid separator 22, and the gas phase outlet 22g is provided at the top of the gas-liquid separator 22.

[0049] The liquid phase outlet 22o of the gas-liquid separator 22 is connected to the reflux inlet 20r of the second distillation column T20 via a line LC. The reflux inlet 20r is provided above the feed inlet 20i. A line LJ is connected to the gas phase outlet 22g of the gas-liquid separator 22. A detoxification device that incinerates compounds in the gas phase may be connected to the line LJ.

[0050] 1, the third distillation column T30 has a feed inlet 30i, a reflux inlet 30r, a column bottom outlet 30b, an extractant inlet 30e, and a column top outlet 30t. The reflux inlet 30r and the extractant inlet 30e are provided above the feed inlet 30i.

[0051] The bottom outlet 20b of the second distillation column T20 and the feed inlet 30i of the third distillation column T30 are connected by a line LD(LL).

[0052] A third drum D30 is connected via line L7 to a top outlet 30t of the third distillation column T30. Line L7 is connected to a third liquefaction means C30 that liquefies the stream discharged from the top outlet 30t of the third distillation column T30. The third drum D30 stores the liquid discharged from the third liquefaction means C30. The third liquefaction means C30 may be, for example, a heat exchanger to which a refrigerant is supplied.

[0053] The third drum D30 is connected to the reflux inlet 30r of the third distillation column T30 via line L9. Furthermore, a product drum (an additional downstream drum) D200 is connected to the third drum D30 via line L8. The product drum D200 is a drum that stores purified propylene oxide supplied from the third drum D30. Such a drum is sometimes called a storage tank. The product drum D200 is provided with a line L10 for discharging purified propylene oxide. At least one product drum D200 may be provided, or multiple product drums may be provided. When multiple product drums are provided to store purified propylene oxide supplied from the third drum D30, the product drums may be connected one by one while switching between them to recover propylene oxide, or multiple product drums may be connected simultaneously to recover propylene oxide.

[0054] A line LE is connected to the bottom outlet 30b of the third distillation column T30. The side of line LE opposite the third distillation column T30 is connected to line LF. Note that the side of line LE opposite the third distillation column T30 is not limited to line LF as long as it is connected to a line for a flow toward the second distillation column T20 or directly to the second distillation column T20. For example, it may be connected to line LB, the second distillation column T20, the liquefaction separation facility LQ, line LC, or a combination of any two or more of these, as long as the extractant can be supplied directly or indirectly to the second distillation column T20. For example, in FIG. 2 , the side of line LE opposite the third distillation column T30 is connected to line LC and line LQ1 of the liquefaction separation facility LQ.

[0055] (Fourth Distillation Column T40) The fourth distillation column T40 has a feed inlet 40i, a reflux inlet 40r, a bottom outlet 40b, and a top outlet 40t. The top outlet 40t of the fourth distillation column T40 is connected to a fourth drum D40 via a line LP. The line LP is connected to a fourth liquefaction means C40 that liquefies the stream discharged from the top outlet 40t of the fourth distillation column T40. The fourth drum D40 stores the liquid discharged from the fourth liquefaction means C40. The fourth liquefaction means C40 may be, for example, a heat exchanger to which a refrigerant is supplied. The fourth drum D40 stores light impurities, such as C5 to C6 hydrocarbons, that accumulate in the extractant.

[0056] The fourth drum D40 is connected to a reflux inlet 40r of the fourth distillation column T40 via a line LW. A liquid discharge line LR is also connected to the fourth drum D40.

[0057] A line LS is connected to the bottom outlet 40b of the fourth distillation column T40. The line LS is connected to the extractant inlet 30e of the third distillation column T30.

[0058] (Pre-stage first distillation column T110 and pre-stage second distillation column (upstream distillation column) T120) The pre-stage first distillation column T110 is a distillation column that recovers unreacted propylene from a stream containing crude propylene oxide obtained by the reaction of a peroxide such as cumene hydroperoxide with propylene (epoxidation step). The pre-stage second distillation column T120 is a distillation column that further recovers heavy components from the stream containing crude propylene oxide.

[0059] The upstream first distillation column T110 has a feed inlet 110i for receiving a stream containing crude propylene oxide via a line LN from the epoxidation reactor EPR, which is a supply source of a stream containing crude propylene oxide for the epoxidation step, a column bottom outlet 110b, and a column top outlet 110t.

[0060] A line L110 for discharging unreacted propylene is connected to a top outlet 110t of the upstream first distillation column T110. A bottom outlet 110b of the upstream first distillation column T110 is connected to a feed inlet 120i of the upstream second distillation column T120 via a line LK.

[0061] The upstream second distillation column T120 has a feed inlet 120i for receiving a stream containing crude propylene oxide via a line LK, a reflux inlet 120r, a column bottom outlet 120b, and a column top outlet 120t.

[0062] A upstream second drum D120 is connected via line LH to the top outlet 120t of the upstream second distillation column T120. Line LH is connected to a upstream second liquefaction means C120 that liquefies the stream discharged from the top outlet 120t of the upstream second distillation column T120. The upstream second drum D120 stores the liquid discharged from the upstream second liquefaction means C120. The upstream second liquefaction means C120 may be, for example, a heat exchanger to which a refrigerant is supplied.

[0063] The upstream second drum D120 and the reflux inlet 120r of the upstream second distillation column T120 are connected via line L1. The reflux inlet 120r is provided above the feed inlet 120i. The upstream second drum D120 and the feed inlet 10i of the first distillation column T10 are connected via line LG.

[0064] The propylene oxide purification apparatus of this embodiment includes at least one of a line LX and a line LY.

[0065] The line LX connects the first drum D10 to the line LG and is configured to supply the liquid in the first drum D10 to the first distillation column T10 via the feed inlet 10i of the first distillation column T10.

[0066] Line LY is a line configured to supply the liquid in the third drum D30 to the first distillation column T10 via the feed inlet 10i of the first distillation column T10. Specifically, for example, line LY may be line LY1 that directly connects the third drum D30 to line LG, or line LY2 that is composed of line L8, a product drum D200, and a line L22 that connects the product drum D200 to line LG and connects the feed inlet 10i of the first distillation column T10 to the third drum D30 via the product drum D200.

[0067] (Method for Propylene Oxide Production) Next, a method for producing propylene oxide using the propylene oxide purification apparatus 100 according to the first embodiment will be described.

[0068] (Epoxidation Step) First, in the epoxidation reactor EPR, peroxide and propylene are reacted in the presence of a known catalyst to obtain a reaction mixture containing propylene oxide and a stream containing unreacted propylene. The reaction mixture may contain a peroxide-derived alcohol (e.g., 2-phenyl-2-propanol) and / or water. For example, an organic peroxide produces an alcohol, and hydrogen peroxide produces water. When the organic peroxide is cumene hydroperoxide, the peroxide-derived alcohol produced in the reaction mixture is 2-phenyl-2-propanol. When the organic peroxide is ethylbenzene hydroperoxide, the peroxide-derived alcohol produced in the reaction mixture is 1-phenylethyl alcohol. When the organic peroxide is tert-butyl hydroperoxide, the peroxide-derived alcohol produced in the reaction mixture is tert-butyl alcohol. The organic peroxide may be used alone or in combination.

[0069] The method for producing propylene used in the epoxidation step is not particularly limited, but propylene produced by the following production methods can be used.

[0070] Examples of methods for producing propylene include cracking naphtha or ethane, fluid catalytic cracking of vacuum diesel, dehydrogenation of propane, disproportionation of ethylene and 2-butene, the MTO (methanol to olefin) reaction of converting methanol or dimethyl ether, the Fischer-Tropsch (FT) synthesis method of reacting carbon monoxide with hydrogen, and dehydration of isopropanol. Other examples include methods for obtaining propylene using alcohols such as methanol, ethanol, isopropanol, butanol, and / or allyl alcohol, as well as acetone and glycerin as raw materials. The raw materials used in the propylene production methods may be derived from fossil resources, plants, or carbon dioxide, natural gas, coal, or other starting materials. Furthermore, propylene produced by chemical recycling technologies including thermal or catalytic decomposition of waste plastics, waste oil, wood, rice straw, corn, sugarcane, algae, and other plants, and waste materials obtained from these materials (sawdust, food waste, paper waste, etc.), gasification of waste materials, alcohol conversion, fermentation, dehydrogenation, hydrogenation, etc. Propylene derived from any of these production methods may be used, or propylene produced by combining two or more of these methods may be used.

[0071] The peroxide, which is the reaction raw material in the epoxidation step, is not particularly limited, and may be, for example, hydrogen peroxide, an organic peroxide, etc. The organic peroxide is not particularly limited, and may be, for example, at least one selected from the group consisting of cumene hydroperoxide, ethylbenzene hydroperoxide, and tert-butyl hydroperoxide, and it is particularly preferable to use cumene hydroperoxide.

[0072] When cumene hydroperoxide is used as the peroxide, a stream containing propylene oxide, 2-phenyl-2-propanol, and unreacted propylene can be obtained by reacting cumene hydroperoxide with propylene.

[0073] In the epoxidation reaction of the present invention, a solid catalyst is used for the purpose of obtaining the target product in high yield and / or for the purpose of carrying out the reaction under mild conditions.

[0074] An example of a catalyst for reacting peroxide with propylene is the so-called titanium-silica catalyst, which contains titanium chemically bonded to silicon oxide.

[0075] The catalyst is not particularly limited as long as it is a known epoxidation catalyst. An example of the catalyst is a titanium-containing silicon oxide catalyst. The titanium-containing silicon oxide is a porous silicate (SiO ２) in which some of the Si atoms are replaced with Ti. Such compounds have a bond represented by —Si—O—Ti. Examples of such compounds include those in which a titanium compound is supported on a silica carrier, those in which the compound is combined with a silicon oxide by a coprecipitation method or a sol-gel method, and zeolite compounds containing titanium. More specific examples include catalysts described in JP-A-2004-195379, JP-A-3731384, and JP-A-3797107; catalysts described in US2005014960 and CN102311363B; Ti-supported silica described in US2007260074; Ti-MCM-41 described in US5783167; Ti-MCM-48 described in JP-A-7-300312; Ti-HMS described in Nature 368 (1994) p321, CN101348472B, CN101307039B, CN101279960B, CN102872847B, and CN103030611B; Ti-SBA-15 described in Journal of Material 14, 1657-1664 (2002), etc.; TS-1 described in Journal of Catalysis 130, 1-8 (1991), etc.; TS-2 described in Applied Catalysis 58, L1-L4 (1991), etc.; Ti-Beta described in Journal of Catalysis 199, 41-47 (2001), etc.; Ti-ZSM-12 described in Zeolites 15, 236-242 (1995), etc.; TAPS0-5 described in Zeolites 15, 228-235 (1995), etc.; The Journal of Physical Examples of such a compound include Ti-MOR described in Chemistry B 102, 9297-9303 (1998) and the like; Ti-ITQ-7 described in Chemical Communications 761-762, (2000) and the like; Ti-UTD-1 described in Zeolites 15, 519-525, (1995) and the like; and Ti-MWW and precursors thereof described in Chemistry Letters 2000, p. 774 and the like (for example, JP-A-2005-262164).

[0076] The catalyst can be used in the form of a slurry or a fixed bed, and a fixed bed is preferred for large-scale industrial operations. When titanium-containing silicon oxide is used as a catalyst, it may be in the form of a powder or a molded body. When the reaction is carried out in a fixed bed, the titanium-containing silicon oxide is preferably in the form of a molded body. This reaction can be carried out by a batch method, a semi-continuous method, or a continuous method.

[0077] The peroxide and propylene are preferably reacted in a solvent. The solvent may be any solvent that is liquid under the temperature and pressure of the reaction and is substantially inert to the reactants and products. Examples of solvents include cumene, aromatic monocyclic compounds (e.g., benzene, toluene, chlorobenzene, orthodichlorobenzene), alkanes (e.g., octane, decane, dodecane), alcohols (methanol, ethanol), and water.

[0078] The temperature of the epoxidation reaction is preferably, for example, 0 to 200°C, and from the viewpoints of reaction rate and economical use of the catalyst, preferably 25 to 200°C, and from the viewpoint of reaction selectivity, preferably 40 to 150°C. The pressure inside each reactor during the epoxidation reaction is preferably adjusted so that the reaction mixture can be maintained in a liquid state. The pressure inside each reactor 1 is not particularly limited, and is preferably, for example, 100 to 10,000 kPa.

[0079] The molar ratio of propylene to peroxide (propylene / peroxide) is not particularly limited, and is preferably, for example, 2 / 1 to 50 / 1, and more preferably 4 / 1 to 10 / 1 from the viewpoint of reducing energy consumption in the step of recovering and recycling propylene while ensuring a good reaction rate of epoxidation.

[0080] (Removal of Unreacted Propylene) The resulting stream containing propylene oxide and alcohol and / or water derived from the peroxide is supplied to the first distillation column T110 in the upstream step via line LN.

[0081] In the upstream first distillation column T110, a stream containing propylene oxide and alcohol and / or water derived from the peroxide is distilled, and unreacted propylene is discharged from the top of the column via line L110, and a stream containing propylene oxide from which the unreacted propylene has been removed is discharged from the bottom of the column via line LK. A step of separating and recovering the unreacted propylene and recycling it as the reaction raw material for the epoxidation step may be further carried out.

[0082] Distillation in the upstream first distillation column T110 is typically performed under conditions that facilitate vaporization of propylene. The distillation conditions vary depending on the temperature and composition of the reaction liquid (the reaction mixture) supplied to the distillation column. For example, typically, the number of theoretical plates is 5 to 200, and the pressure in the distillation column is preferably 0 to 5 MPa, more preferably 0 to 3 MPa, in terms of gauge pressure. The column top temperature is preferably −50 to 150°C, more preferably −30 to 140°C, and the column bottom temperature is preferably 50 to 200°C, more preferably 80 to 200°C. Alternatively, a method of distilling propylene in stages using multiple distillation columns may be used.

[0083] The unreacted propylene separated and recovered in this manner can be mixed with newly supplied propylene and fed to the epoxidation reactor.

[0084] As described above, the peroxide is not particularly limited, but for example, when cumene hydroperoxide is used as the peroxide, a stream containing 2-phenyl-2-propanol and cumene is removed. A method for removing a stream containing 2-phenyl-2-propanol and cumene will be described.

[0085] (Removal of 2-phenyl-2-propanol and cumene) In the upstream second distillation column T120, a stream containing propylene oxide supplied via line LK is distilled, and 2-phenyl-2-propanol and cumene are discharged from the bottom of the column via line LLZ, and a stream containing propylene oxide is discharged from the top of the column via line LH.

[0086] A stream containing propylene oxide is liquefied by a first-step second liquefaction means C120 and stored in a first-step second drum D120 (a crude propylene oxide supply source). By returning the liquid in the first-step second drum D120 via a line L1 to a reflux inlet 120r of the first-step second distillation column T120 at an appropriate reflux ratio, an appropriate removal rate of 2-phenyl-2-propanol and cumene can be achieved.

[0087] Examples of suitable distillation conditions for the upstream second distillation column T120 include, for example, typically 5 to 200 theoretical plates, a gauge pressure in the distillation column of preferably 0 to 3 MPa, more preferably 0 to 1 MPa, a column top temperature of preferably 10 to 80°C, more preferably 30 to 60°C, and a column bottom temperature of preferably 100 to 250°C, more preferably 150 to 200°C.

[0088] (Removal of High-Boiling Components) Next, the crude propylene oxide stored in the upstream second drum D120 is supplied to the first distillation column T10 via line LG.

[0089] (Crude Propylene Oxide) In addition to propylene oxide, crude propylene oxide contains impurities. Examples of the impurities include organic acids such as formic acid, acetic acid, and propionic acid; esters such as methyl formate; water; alcohols such as methanol, ethanol, n-propyl alcohol, and isopropyl alcohol; glycols such as propylene glycol; ketones such as acetone; aldehydes such as formaldehyde, acetaldehyde, and propionaldehyde; hydrocarbons having 1 to 4 carbon atoms (referred to as C1-C4 hydrocarbons) such as methane, ethane, propane, propylene, cyclopropane, n-butane, isobutane, 1-butene, 2-butene, and butadiene; and hydrocarbons such as pentanes, pentenes, pentadienes, hexanes, hexenes, and hexadienes (referred to as C5-C6 hydrocarbons).

[0090] In the first distillation column T10, crude propylene oxide is distilled to discharge high-boiling components having boiling points higher than that of propylene oxide from the column bottom outlet 10b, and a propylene oxide-containing stream from which the high-boiling components have been removed is discharged from the column top outlet 10t.

[0091] Examples of impurities having a boiling point higher than that of propylene oxide include organic acids such as formic acid, acetic acid, and propionic acid; water; alcohols such as methanol, ethanol, n-propyl alcohol, and isopropyl alcohol; glycols such as propylene glycol; ketones such as acetone; and hydrocarbons such as pentanes, pentenes, pentadienes, hexanes, hexenes, and hexadienes (referred to as C5 to C6 hydrocarbons).

[0092] Examples of suitable operating conditions for the first distillation column T10 include 5 to 200 theoretical plates, an operating pressure of 0.01 to 5 MPa absolute, and a temperature of 0 to 300°C.

[0093] The stream discharged via line LA is liquefied in a first liquefaction means C10 and stored in a first drum D10.

[0094] A portion of the stream discharged from the top outlet 10t can be refluxed to the first distillation column T10 via line L3 to adjust the degree of removal of high boiling point components.

[0095] (Extractive Distillation) The stream in first drum D10 is then supplied via line LF to feed inlet 20i of second distillation column T20 for distillation in the presence of an extractant supplied directly or indirectly via line LE.

[0096] Examples of extractants include saturated hydrocarbons having 7 to 10 carbon atoms, such as heptane, octane, nonane, and decane; aromatic hydrocarbons, such as toluene, ethylbenzene, n-propylbenzene, and isopropylbenzene; ketones, such as acetone; and glycols, such as ethylene glycol and propylene glycol. Among these, saturated hydrocarbons and aromatic hydrocarbons having 7 to 10 carbon atoms are preferred, and saturated hydrocarbons having 7 to 10 carbon atoms are most suitable. Addition of such an extractant increases the relative volatility of low-boiling components, such as methanol, water, acetaldehyde, and hydrocarbons, from propylene oxide, facilitating their separation.

[0097] In the second distillation column T20, distillation is carried out in the presence of an extractant, and a stream containing water, formaldehyde, acetaldehyde, methanol, methyl formate, etc. is discharged from a top outlet 20t, and a stream containing propylene oxide and the extractant is discharged from a bottom outlet 20b.

[0098] Examples of suitable distillation conditions for the second distillation column T20 include 5 to 200 theoretical plates, an operating pressure of 0.01 to 5 MPa absolute, and a temperature of 0 to 300° C. The amount of extractant supplied to the second distillation column can be 0.1 to 20 times the weight of the propylene oxide supplied.

[0099] Next, the stream discharged from the top outlet of the second distillation column T20 via line LB is supplied to the inlet LQi of the liquefaction separation equipment LQ, where at least a portion of the stream is liquefied and separated into gas and liquid, and the gas phase is discharged from the gas phase outlet LQg and the liquid phase is discharged from the liquid phase outlet LQl.

[0100] Specifically, as shown in Fig. 2, the stream discharged from the top outlet 20t is first cooled in a cooler 26 provided in a line LQ1 to liquefy a portion of the stream. Specifically, it is preferable to lower the temperature of the stream to a temperature equal to or lower than the boiling point of propylene oxide to liquefy at least a portion of the propylene oxide.

[0101] Alternatively, the liquid extractant stream supplied via line LE may be supplied from connection LBJ1 to line LQ1, and a portion of the gas in the stream may be dissolved / absorbed into the liquid phase of the extractant, i.e., a portion of the gas in the stream may be liquefied. Specifically, it is preferred to liquefy a portion of the propylene oxide gas in the stream, i.e., to dissolve / absorb it into the liquid phase.

[0102] In the gas-liquid separator 22, the mixture of the streams in lines LB and LE is separated into a gas phase and a liquid phase. The gas phase is then discharged to the outside via a gas phase outlet 22g and line LJ. This gas phase mainly contains C1 to C4 hydrocarbons. Examples of C1 to C4 hydrocarbons include aldehydes such as formaldehyde, acetaldehyde, and propionaldehyde; esters such as methyl formate; water; alcohols such as methanol; and hydrocarbons with 1 to 4 carbon atoms, such as methane, ethane, propane, cyclopropane, propylene, n-butane, isobutane, 1-butene, 2-butene, and butadiene. A detoxification device for removing C1 to C4 hydrocarbons can be connected to line LJ, allowing for detoxification treatment as needed. Examples of detoxification devices include an adsorption device that adsorbs C1 to C4 hydrocarbons and a combustion device that combusts C1 to C4 hydrocarbons. One or more abatement devices for removing C1 to C4 hydrocarbons can be connected to the line LJ.

[0103] A liquid phase stream is also supplied to the reflux inlet 20r of the second distillation column T20 via the liquid phase outlet 22o and the line LC. If necessary, a liquid stream (FS) of the extractant supplied via the line LE2 may be supplied to the line LC.

[0104] The operating conditions of the gas-liquid separator 22 may be any conditions that allow an interface between the gas phase and the liquid phase to be formed, and preferably the temperature is 0 to 80° C. and the pressure is normal pressure to 2 MPa.

[0105] (Separation of Extractant) Returning to FIG. 1, the stream containing propylene oxide and extractant discharged from the bottom outlet 20b of the second distillation column T20 is then supplied to the feed inlet 30i of the third distillation column T30 via line LD.

[0106] In the third distillation column T30, a stream containing the extractant and propylene oxide is distilled, and a purified propylene oxide stream is discharged from a top outlet 30t via line L7, while an extractant stream is discharged from a bottom outlet 30b via line LE and / or line LT. The extractant stream can be supplied directly or indirectly to the second distillation column T20 via line LE, etc., as necessary. Furthermore, an extractant with a higher purity than the extractant discharged via line LE, which is supplied from a fourth distillation column T40 (described in detail below) via line LS, can be supplied to the third distillation column T30 via an extractant inlet 30e, thereby further increasing the purity of propylene oxide.

[0107] The stream discharged via line L7 is liquefied in third liquefaction means C30 and stored in third drum D30. A portion of the stream discharged from top outlet 30t can be refluxed to third distillation column T30 via line L9 to adjust the degree of removal of the extractant. The liquid in third drum D30 can be supplied to product drum D200 as needed.

[0108] Examples of suitable operating conditions for the third distillation column T30 include 5 to 200 theoretical plates, an operating pressure of 0.01 to 5 MPa absolute, and a temperature of 0°C to 300°C.

[0109] In this way, purified propylene oxide can be obtained in the third drum D30 and the product drum D200.

[0110] (Purification of Extractant) In this embodiment, in the fourth distillation column T40, a portion of the extractant stream discharged from the bottom outlet 30b of the third distillation column T30 and supplied via line LT is distilled, and a stream containing primarily components with lower boiling points than the extractant is discharged from the top outlet 40t and line LP, while a stream of extractant with a higher purity than the stream in line LP is discharged from the bottom outlet 40b. The extractant stream discharged from the bottom outlet 30b of the third distillation column T30 often contains at least a portion of components with lower boiling points than the extractant (e.g., hydrocarbons such as pentanes, pentenes, pentadienes, hexanes, hexenes, and hexadienes (referred to as C5-C6 hydrocarbons)). The fourth distillation column T40 can produce a high-purity extractant stream with reduced concentrations of the aforementioned compounds compared to the stream in line LE. This stream can be fed via line LS to the extractant inlet 30e of the third distillation column T30 to further increase the purity of the propylene oxide discharged via line L7.

[0111] Examples of suitable operating conditions for the fourth distillation column T40 include 5 to 200 theoretical plates, an operating pressure of 0.01 to 5 MPa absolute, and a temperature of 0 to 300°C.

[0112] A portion of the stream discharged from the top outlet 40t, liquefied, and stored in the fourth drum D40 can be refluxed via line LW to the reflux inlet 40r of the fourth distillation column T40, thereby adjusting the purity of the extractant contained in the stream in line LS.

[0113] According to this embodiment, crude propylene oxide is distilled in a first distillation column T10, and high-boiling components having a boiling point higher than that of propylene oxide are discharged from a bottom outlet 10b, and a propylene oxide-containing stream with the high-boiling components reduced is discharged from a top outlet 10t. In a second distillation column T20, streams from lines LA and LF are distilled together with an extractant, and a stream containing C1-C4 hydrocarbons and propylene oxide is discharged from a top outlet 20t, and a stream containing the extractant and propylene oxide is discharged from the bottom. Here, more than half of the total weight of propylene oxide in the streams from lines LA and LF is contained in the stream from line LD. In a third distillation column T30, the stream from line LD is distilled, and a stream containing the extractant is discharged from a bottom outlet 30b, and a purified propylene oxide stream is discharged from a top outlet 30t.

[0114] In addition, the liquefaction separation equipment LQ liquefies at least a portion of the flow in line LB, and separates the flow containing a liquid phase and a gas phase into a liquid phase and a gas phase.The liquid phase flow is returned to the second distillation column T20 via the liquid phase outlet 22o and line LC, while the gas phase flow can be discharged from the liquefaction separation equipment LQ via the gas phase outlet 22g without being returned to the second distillation column T20.

[0115] As a result, high-boiling point components can be reduced from the crude propylene oxide in the first distillation column T10, and C1 to C4 hydrocarbons such as aldehydes such as formaldehyde, acetaldehyde, and propionaldehyde; esters such as methyl formate; water; alcohols such as methanol; and hydrocarbons having 1 to 4 carbon atoms such as methane, ethane, propane, cyclopropane, propylene, n-butane, isobutane, 1-butene, 2-butene, and butadiene can be removed in the second distillation column T20 and liquefaction separation facility LQ, and high-purity propylene oxide can be obtained from the top of the third distillation column T30.

[0116] In particular, the liquefaction separation equipment LQ liquefies at least a portion of the propylene oxide contained in the stream in line LB, separates it from the gas phase, and returns it to the second distillation column T20, thereby reducing the loss of propylene oxide while removing C1 to C4 hydrocarbons. Because the C1 to C4 hydrocarbons are distributed to the top outlet 30t together with propylene oxide in the third distillation column T30, it is difficult to separate the C1 to C4 hydrocarbons from the propylene oxide when the C1 to C4 hydrocarbons are supplied to the third distillation column T30. However, according to this embodiment, by separating the gas containing C1 to C4 hydrocarbons from the propylene oxide in the liquefaction separation equipment LQ, the amount of C1 to C4 hydrocarbons in the propylene oxide obtained from the third distillation column T30 can be reduced, thereby increasing the purity of the propylene oxide.

[0117] (Function) During the purification of propylene oxide, some disturbance may occur. For example, the temperature and pressure conditions of the first distillation column T10, the second distillation column T20, and / or the third distillation column T30 may fluctuate, or the purity of the crude propylene oxide supplied to these columns may fluctuate. In such cases, the purification conditions, such as distillation, are not optimized, and the purity of the purified propylene oxide stored in the first drum D10 of the first distillation column T10 and / or the third drum D30 of the third distillation column T30 often decreases below the respective purities in the steady state. Even if crude propylene oxide of lower purity than expected stored in the first drum D10 is sent directly to the second distillation column T20 under normal operating conditions, it is difficult to obtain the expected product in the third drum D30 of the third distillation column T30. This requires a considerable degree of resetting of the operating conditions, which requires advanced operations and effort. Furthermore, crude propylene oxide of lower purity than expected stored in the third drum D30 cannot be sent to the product drum D200, etc.

[0118] Therefore, in such cases, the low-purity propylene oxide in the first drum D10 and the third drum D30 has often been discarded.

[0119] In contrast, the propylene oxide purification apparatus according to this embodiment has line LX, line LY1, or line LY2, so that a stream containing propylene oxide of a purity lower than expected and stored in first drum D10 and third drum D30 can be re-supplied from feed inlet 10i to first distillation column T10, and then passed through second distillation column T20 and third distillation column T30 in that order for purification. In this case, there is little need to reset the operating conditions of each purification apparatus, and re-purification can be performed efficiently. Therefore, the product yield can be increased.

[0120] Specifically, for example, when the purity of the propylene oxide-containing liquid stored in at least one of the first drum D10 and the third drum D30 falls below a predetermined threshold, the propylene oxide-containing liquid stored in at least one of the first drum D10 and the third drum D30 can be returned to the first distillation column T10 via the line LX or the lines LY1 and / or LY2, and purified.

[0121] Second Embodiment Next, a second embodiment of the propylene oxide purification device 110 will be described with reference to Fig. 3. In this section, only differences from the first embodiment will be described, and a description of the same points as the first embodiment will be omitted.

[0122] The propylene oxide purification apparatus 110 of this embodiment differs from the first embodiment in that the lines LX, LY1, and LY2 are connected to the upstream second drum D120 of the upstream second distillation column T120 instead of the line LG.

[0123] In this embodiment, too, the unexpected low-purity propylene oxide stream from the first drum D10 and the third drum D30 can be supplied to the feed inlet 10i of the first distillation column T10 via the upstream second drum D120 and line LG, thereby achieving the same effects.

[0124] Third Embodiment Next, a third embodiment of the propylene oxide purification device 120 will be described with reference to Fig. 4. In this section, only differences from the first embodiment will be described, and a description of the same points as the first embodiment will be omitted.

[0125] The propylene oxide purification apparatus of this embodiment differs from the first embodiment in that an intermediate drum D130 is provided in the line LG, and the lines LX and LY1 are connected to the intermediate drum D130 instead of the line LG. Note that the line LY2 may also be connected to the intermediate drum D130 instead of the line LG. Furthermore, another drum may be installed between the intermediate drum D130 and the line LG.

[0126] In this embodiment, too, a low-purity propylene oxide stream unexpectedly present in the first drum D10 and the third drum D30 can be supplied to the feed inlet 10i of the first distillation column T10 via the intermediate drum D130 and line LG, thereby achieving the same advantageous effects. Furthermore, in this embodiment, because a constant amount of propylene oxide can be stored in the intermediate drum D130, there is also the advantage that, even if there is an increase or decrease in the propylene oxide-containing stream supplied to the intermediate drum D130 from line LX and line LY1, the amount of liquid supplied to the first distillation column T10 via line LG does not fluctuate suddenly, and can be supplied stably.

[0127] There may be a line LGG for returning the flow in the intermediate drum D130 to the second drum D120 in the preceding process.

[0128] Fourth Embodiment Next, a fourth embodiment of the propylene oxide purification device 130 will be described with reference to Fig. 5. In this section, only the differences from the third embodiment will be described, and a description of the same points as the third embodiment will be omitted.

[0129] The propylene oxide purification apparatus of this embodiment differs from the third embodiment in that the side cut outlet 10s, rather than the top outlet 10t of the first distillation column T10, is connected to the first drum D10 via a line (first side cut line) LA. Since the stream discharged from the side cut outlet 10s is usually a liquid, a liquefaction means is not required between the side cut outlet 10s and the first drum D10, but a liquefaction means may be present. A line LLA is connected to the top outlet 10t of the first distillation column T10.

[0130] In this first distillation column T10, a stream containing propylene oxide is discharged from a side cut outlet 10s, and components having a boiling point lower than that of propylene oxide are discharged from a top outlet 10t. Although not shown, the line LLA may be equipped with a liquefaction means for liquefying the stream discharged from the side cut outlet 10s, a drum for storing the liquid, and a reflux line for refluxing the liquid in the drum to the first distillation column T10.

[0131] In this embodiment, too, the unexpected low-purity propylene oxide stream from the first drum D10 and the third drum D30 can be supplied to the feed inlet 10i of the first distillation column T10 via the intermediate drum D130 and line LG, thereby achieving the same advantageous effects.

[0132] Such a change may be made not only to the third embodiment but also to other embodiments.

[0133] Fifth Embodiment Next, a fifth embodiment of a propylene oxide purification device 140 will be described with reference to Fig. 6. In this section, only differences from the third embodiment will be described, and a description of the same points as the third embodiment will be omitted.

[0134] The propylene oxide purification apparatus of this embodiment differs from the third embodiment in that the side cut outlet 30s, rather than the top outlet 30t of the third distillation column T30, is connected to the third drum D30 via a line (third side cut line) L7. Since the stream discharged from the side cut outlet 30s is usually a liquid, a liquefaction means is not required between the side cut outlet 30s and the third drum D30, but a liquefaction means may be present. A line LLB is connected to the top outlet 30t of the third distillation column T30.

[0135] In such a third distillation column T30, a stream containing propylene oxide is discharged from a side cut outlet 30s, and components having a boiling point lower than that of propylene oxide are discharged from a top outlet 30t. Although not shown, line LLB may be equipped with a liquefaction means for liquefying the stream discharged from the side cut outlet 30s, a drum for storing the liquid, and a reflux line for refluxing the liquid in the drum to the third distillation column T30.

[0136] In this embodiment, too, the unexpected low-purity propylene oxide stream from the first drum D10 and the third drum D30 can be supplied to the feed inlet 10i of the first distillation column T10 via the intermediate drum D130 and line LG, thereby achieving the same advantageous effects.

[0137] Such a change may be made not only to the third embodiment but also to other embodiments.

[0138] Sixth Embodiment Next, a sixth embodiment of a propylene oxide purification apparatus 150 will be described with reference to Fig. 7. In this section, only differences from the third embodiment shown in Fig. 4 will be described, and a description of the same points as the third embodiment will be omitted.

[0139] In this embodiment, a sixth distillation column (auxiliary distillation column) T60 is provided in a line LG connecting the feed inlet 10i of the first distillation column T10 and the intermediate drum D130.

[0140] (Sixth Distillation Column (Auxiliary Distillation Column) T60) The sixth distillation column (auxiliary distillation column) T60 has a feed inlet 60i, a reflux inlet 60r, a column bottom outlet 60b, and a column top outlet 60t. The intermediate drum D130 is connected to the feed inlet 60i of the sixth distillation column (auxiliary distillation column) T60 via a line LG1 (LG).

[0141] A sixth drum (auxiliary drum) D60 is connected via line LG2 (LG) to a top outlet 60t of the sixth distillation column (auxiliary distillation column) T60. Line LG2 is connected to liquefaction means C60, which liquefies the stream discharged from the top outlet 60t of the sixth distillation column (auxiliary distillation column) T60. The sixth drum (auxiliary drum) D60 stores the liquid discharged from the liquefaction means C60. The liquefaction means C60 may be, for example, a heat exchanger to which a refrigerant is supplied.

[0142] The sixth drum (auxiliary drum) D60 is connected to the feed inlet 10i of the first distillation column T10 via line LG3 (LG). The sixth drum (auxiliary drum) D60 is further connected to the reflux inlet 60r of the sixth distillation column (auxiliary distillation column) T60 via line L60. The reflux inlet 60r is located above the feed inlet 60i. A line LM is connected to the bottom outlet 60b of the sixth distillation column (auxiliary distillation column) T60. High boiling components are discharged from line LM. By providing the sixth distillation column (auxiliary distillation column) T60 in addition to the first distillation column T10, the load on the first distillation column T10 can be reduced, making it easier to remove high boiling components. The sixth drum D60 is further connected to the intermediate drum D130 via line LX2.

[0143] In this embodiment, since lines LX, LY1, and LY2 are provided, an unexpected low-purity propylene oxide stream from the first drum D10 and the third drum D30 can be supplied to the feed inlet 10i of the first distillation column T10 via the intermediate drum D130 and line LG, achieving the same advantageous effects. Furthermore, since line LX2 is provided in this embodiment, an unexpected low-purity propylene oxide stream from the sixth drum D60 can be supplied to the feed inlet 10i of the first distillation column T10 via the intermediate drum D130, line LG, and the sixth distillation column (auxiliary distillation column) T60, similarly increasing the product yield.

[0144] Such a change may be made not only to the third embodiment but also to other embodiments.

[0145] Seventh Embodiment Next, a seventh embodiment of a propylene oxide purification apparatus 160 will be described with reference to Fig. 8. In this section, only differences from the third embodiment shown in Fig. 4 will be described, and a description of the same points as the third embodiment will be omitted.

[0146] In this embodiment, a seventh distillation column (auxiliary distillation column) T70 is provided in a line LG connecting the intermediate drum D130 and the feed inlet 10i of the first distillation column T10.

[0147] (Seventh Distillation Column (Auxiliary Distillation Column) T70) The seventh distillation column (auxiliary distillation column) T70 has a feed inlet 70i, a column bottom outlet 70b, and a column top outlet 70t. The intermediate drum D130 is connected to the feed inlet 70i of the seventh distillation column (auxiliary distillation column) T70 via a line LG1 (LG). The seventh distillation column (auxiliary distillation column) T70 may have a reflux inlet 70r.

[0148] In Figure 8, low-boiling components are withdrawn as a vapor phase directly from the top outlet 70t of the seventh distillation column (auxiliary distillation column) T70 via line L70. The vapor phase components withdrawn here mainly contain C1 to C4 hydrocarbons. Examples of C1 to C4 hydrocarbons include aldehydes such as formaldehyde, acetaldehyde, and propionaldehyde; esters such as methyl formate; water; alcohols such as methanol; and hydrocarbons having 1 to 4 carbon atoms, such as methane, ethane, propane, cyclopropane, propylene, n-butane, isobutane, 1-butene, 2-butene, and butadiene.

[0149] As shown by the dotted line in FIG. 8 , a seventh drum (auxiliary drum) D70 may be connected to the top outlet 70t of the seventh distillation column (auxiliary distillation column) T70 via line L70. In this case, line L70 is provided with a liquefaction means C70 that liquefies the stream discharged from the top outlet 70t of the seventh distillation column (auxiliary distillation column) T70, and the seventh drum D70 stores the liquid discharged from the liquefaction means C70. The liquefaction means C70 may be, for example, a heat exchanger to which a refrigerant is supplied. In this case, the seventh drum D70 is connected to a reflux inlet 70r of the seventh distillation column (auxiliary distillation column) T70 via line L71. The reflux inlet 70r is located above the feed inlet 70i. A liquid discharge line L73 is connected to the seventh drum D70. Components with boiling points lower than propylene oxide are discharged from line L73. The seventh drum D70 is further connected to an intermediate drum D130 via a line LX3.

[0150] The bottom outlet 70b of the seventh distillation column (auxiliary distillation column) T70 is connected to the feed inlet 10i of the first distillation column T10 via a line LG2 (LG, LL).

[0151] In this embodiment, since lines LX, LY1, and LY2 are provided, an unexpected low-purity propylene oxide stream from the first drum D10 and the third drum D30 can be supplied to the feed inlet 10i of the first distillation column T10 via the intermediate drum D130, line LG1, the seventh distillation column (auxiliary distillation column) T70, and line LG2, achieving the same advantageous effects. Furthermore, since line LX3 is provided in this embodiment, an unexpected low-purity propylene oxide stream from the seventh drum D70 can be supplied to the feed inlet 10i of the first distillation column T10 via the intermediate drum D130, line LG1, the seventh distillation column (auxiliary distillation column) T70, and line LG2, achieving the same high product yield.

[0152] Such a change may be made not only to the third embodiment but also to other embodiments.

[0153] (First Modified Embodiment of Liquefaction Separation Facility LQ) A first modified embodiment of the liquefaction separation facility LQ will be described with reference to FIG.

[0154] The liquefaction separation equipment LQ of this embodiment differs from the embodiment of Figure 2 in that it is provided with a connection part LBJ2 that connects the line LH connected to the water supply source with the line LB, and in that it is provided with a three-phase separator 23 instead of the gas-liquid separator 22.

[0155] In this embodiment, the connection part LBJ2 is provided between the line LB, i.e., the cooler 26, and the second distillation column T20, but it may also be provided between the line LQ1, i.e., the cooler 26, and the three-phase separator 23.

[0156] Line LH supplies liquid or gaseous water from connection LBJ2 to line LB. The amount of water supplied can be determined so that the ratio of the amount of water to the weight of stream (F2) supplied from top outlet 20t satisfies water / top stream = 0.01 / 1 to 1 / 1.

[0157] The three-phase separator 23 has a fluid inlet 23i, a gas phase outlet 23g, an oil phase outlet 23o, and an aqueous phase outlet 23w, and separates the fluid into a gas phase, an aqueous phase, and an oil phase. The fluid inlet 23i is connected to a line LQ1, the gas phase outlet 23g is connected to a line LJ, the oil phase outlet 23o is connected to a line LC, and the aqueous phase outlet 23w is connected to a line L5.

[0158] Specifically, as shown in Fig. 9, the three-phase separator 23 can be a drum having a main drum 23c and a boot portion 23b protruding downward from the main drum 23c. In such a three-phase separator 23, an oil-water interface can be formed in the boot portion 23b, and a gas-liquid (gas-oil) interface can be formed in the main drum 23c. A fluid inlet 23i can be provided in the upper part of the main drum 23c, an oil phase outlet 23o can be provided in the lower part of the main drum 23c, and an aqueous phase outlet 23w can be provided in the lower part of the boot portion 23b.

[0159] In this embodiment, liquid or gaseous water is supplied from line LH to a connection point LBJ2 of line LB. Connection point LBJ2 brings water into contact with the stream supplied from the top outlet 20t of second distillation column T20 via line LB, thereby dissolving / absorbing at least a portion of the stream into water and liquefying a portion of the gas in the stream. Specifically, a portion of the propylene oxide gas and water-soluble / absorbable components in the stream (aldehydes such as formaldehyde and acetaldehyde, alcohols such as methanol, glycols such as propylene glycol, ketones such as acetone, esters such as methyl formate, etc.) can be dissolved / absorbed into water and liquefied.

[0160] Furthermore, in three-phase separator 23, the mixture of the stream through line LB, the water through line LH, and the stream through line LE is separated into a gas phase, an aqueous phase, and an oil phase. The gas phase is then discharged to the outside via line LJ, the oil phase is returned to the reflux inlet 20r of second distillation column T20 via line LC, and the aqueous phase is discharged to the outside via line L5 without being returned to second distillation column T20. A known water treatment device can be connected to line L5.

[0161] According to this embodiment, at least a portion of the flow in line LB is liquefied by the cooler 26, and the connection parts LBJ2 and LBJ1, and the fluid containing liquid and gas is separated into a gas phase, an aqueous phase, and an oil phase in the three-phase separator 23. The oil phase is refluxed from the oil phase outlet (liquid phase outlet) 23o via line LC to the second distillation column T20, the aqueous phase is discharged from the aqueous phase outlet 23w via line L5, and the gas phase is discharged from the gas phase outlet 23g in the same manner as in the first embodiment.

[0162] In this embodiment, particularly, by supplying water to line LB via connection LBJ2, water-soluble / absorbable components of the gas flowing through line LB are dissolved in / absorbed by water. Specifically, some of the water-soluble / absorbable components in the flow (aldehydes such as formaldehyde and acetaldehyde, alcohols such as methanol, glycols such as propylene glycol, ketones such as acetone, esters such as methyl formate, etc.) are dissolved in / absorbed by the aqueous phase. The aqueous phase separated from the oil phase by three-phase separator 23 is discharged without being returned to second distillation column T20, thereby separating the water-soluble / absorbable components and further increasing the purity of the purified propylene oxide.

[0163] In this embodiment, by supplying a liquid containing an extractant via line LBJ1, it becomes easier to separate propylene oxide and water in the three-phase separator 23, and the loss of propylene oxide can be minimized.

[0164] The line LE supplies a liquid or gaseous extractant to the line LB from the connection point LBJ1. The amount of the extractant supplied to the line LB is preferably such that the ratio of the amount of the extractant to the weight of the stream (F2) supplied from the top outlet 20t is 0.01 / 1 to 10 / 1, more preferably 0.1 / 1 to 10 / 1.

[0165] (Second Modified Example of Liquefaction Separation Facility) Next, a second modified example of the liquefaction separation facility LQ will be described with reference to FIG.

[0166] This embodiment differs from the embodiment shown in FIG. 2 in that it mainly comprises a fifth distillation column (liquefaction section) T50 instead of the gas-liquid separator.

[0167] Line LB connects the top outlet 20t of the second distillation column T20 to the inlet 26i of the cooler C26 (the inlet LQi of the liquefaction separation facility LQ).

[0168] The fifth distillation column T50 has a feed inlet 50i, a column top outlet (vapor phase outlet) 50t, and a column bottom outlet (liquid phase outlet) 50b. A line LQ1 connects the outlet 26o of the cooler C26 to the feed inlet 50i of the fifth distillation column T50. The fifth distillation column T50 may have a reflux inlet 50r.

[0169] The line LQ1 is provided with a connection part LBJ1 with the line LE, similar to the embodiment shown in Fig. 2. The line LE may be provided with an intermediate drum D510.

[0170] The cooler C26 is preferably provided between the junction LBJ1 and the second distillation column T20, but may also be provided between the junction LBJ1 and the fifth distillation column T50.

[0171] In FIG. 10, low boiling gases are extracted from the top outlet 50t of the fifth distillation column T50 via a line LJ.

[0172] As shown by the dotted line in Figure 10, the top outlet 50t of the fifth distillation column T50 and the drum D520 may be connected by a line LJ. In this case, the line LJ is provided with a liquefaction means C50 that liquefies the stream discharged from the top outlet 50t of the fifth distillation column T50, and the drum D520 stores the liquid discharged from the liquefaction means C50. The liquefaction means C50 may be, for example, a heat exchanger to which a refrigerant is supplied. In this case, the drum D520 and the reflux inlet 50r of the fifth distillation column T50 are connected by a line L19. The reflux inlet 50r is provided above the feed inlet 50i. A line L20 for discharging the stream is also connected to the drum D520.

[0173] The bottom outlet 50b of the fifth distillation column T50 is connected to the reflux inlet 20r of the second distillation column T20 via a line LC. An intermediate drum D530 may be provided on the line LC.

[0174] In this embodiment, a mixture of a stream containing C1-C4 hydrocarbons and propylene oxide discharged from the top outlet 20t of the second distillation column T20 and a stream of extractant supplied from line LE is distilled in a fifth distillation column T50, and a stream mainly containing C1-C4 hydrocarbons is discharged via the top outlet 50t and line LJ, and a stream containing the extractant and propylene oxide with reduced C1-C4 hydrocarbons is discharged from the bottom outlet 50b to the reflux inlet 20r of the second distillation column T20.

[0175] An example of suitable operating conditions for the fifth distillation column T50 is temperature and pressure conditions that allow C1 to C4 hydrocarbons in the fluid flowing in from the feed inlet 50i to be extracted through the column top outlet 50t, and propylene oxide and the extractant to be extracted through the column bottom outlet 50b. Specifically, the number of theoretical plates is 5 to 200, the operating pressure is 0.01 to 5 MPa absolute, and the temperature is 0°C to 100°C.

[0176] As a result, in the fifth distillation column T50, the propylene oxide in the stream supplied from the top outlet 20t of the second distillation column T20 is liquefied and discharged as a liquid from the bottom outlet 50b corresponding to the liquid phase outlet, while the C1 to C4 hydrocarbons in the stream remain in the gaseous state and are discharged from the top outlet 50t corresponding to the gas phase outlet.

[0177] 2, in this embodiment, the stream discharged from the top outlet 20t of the second distillation column T20 can be cooled in a cooler 26 provided in line LQ1 to liquefy a portion of the stream. Also, the liquid stream of the extractant supplied via line LE can be supplied from a connection point LBJ1 to line LQ1 to liquefy a portion of the gas in the stream.

[0178] According to this embodiment, as in the embodiment of FIG. 2, at least a portion of the propylene oxide contained in the stream supplied via line LB is liquefied in liquefaction separation facility LQ, separated from the gas phase, and returned to second distillation column T20, thereby making it possible to reduce loss of propylene oxide while removing C1 to C4 hydrocarbons.

[0179] The present invention is not limited to the above-described embodiment, and various modifications can be made.

[0180] (Liquefaction separation equipment LQ) In the above embodiment, the liquefaction separation equipment LQ does not have to be provided. In that case, instead of the liquefaction separation equipment LQ, a normal liquid discharge system can be provided, for example, having a flow cooler, a liquid storage drum, a reflux line from the drum to the second distillation column, and a liquid discharge line from the drum.

[0181] (Line LE) When the liquefaction separation equipment LQ is not provided, or when the liquefaction separation equipment LQ does not have the connection part LBJ1, the line LE may be connected to the line LF, the line LB, the line LC, or the second distillation column T20 to supply the extractant. Even when the liquefaction separation equipment LQ has the connection part LBJ1 as shown in Figure 2, the extractant flow from the line LE may be supplied to the line LF, the line LC, or the second distillation column T20 via a line LE2 branching off from the line LE.

[0182] (Fourth Distillation Column T40) The apparatus does not necessarily have to include the fourth distillation column T40. In this case, the extractant may be supplied to the extractant inlet 30e of the third distillation column T30, or may be supplied to, for example, line LE.

[0183] (Second Distillation Column T20) The apparatus does not necessarily have to include the second distillation column T20. For example, the apparatus can be implemented as long as it includes an extractant-using separation means that contacts the liquid discharged from the first drum D10 with an extractant to separate the liquid into a stream containing light components and a stream containing propylene oxide and the extractant, and supplies the stream containing propylene oxide and the extractant to the feed inlet of the third distillation column T30.

[0184] (Gas-Liquid Separator, Three-Phase Separator, and Oil-Water Separator) For example, the configurations of the gas-liquid separator 22 and the three-phase separator 23 are not limited to those described above. The gas-liquid separator 22 may be any suitable device as long as it can separate a mixture of gas and liquid phases into the gas and liquid phases and separate and discharge the gas and liquid phases. The three-phase separator 23 may be any suitable device as long as it can separate a mixture of gas, water, and oil phases into the gas, water, and oil phases and separate and discharge the gas, water, and oil phases. Instead of the three-phase separator, a combination of a gas-liquid separator and an oil-water separator that separates the oil and water phases may be used. The oil-water separator may be any suitable device as long as it can separate a mixture of oil and water phases into the oil and water phases and separate and discharge the oil and water phases. For example, the shape of each separator is not particularly limited. If the separator has a drum shape, it may be vertical or horizontal, and may have baffles for gas-liquid separation and oil-water separation inside the separator.

[0185] (Liquefaction Section of Liquefaction Separation Equipment LQ) In the above embodiment, the line LB of the liquefaction separation equipment LQ includes both the connection LBJ1 and the cooler 26 as a liquefaction section, but may include only one of them. The line LB may include two or more coolers. The connection LBJ1 and the cooler 26 that are not provided in the line LB may be provided in another component of the liquefaction separation equipment LQ, i.e., the gas-liquid separator 22. Alternatively, the line LB of the liquefaction separation equipment LQ may not include either the connection LBJ1 or the cooler 26, but may include the connection LBJ1 and / or the cooler 26 in another component of the liquefaction separation equipment LQ, i.e., the gas-liquid separator 22. If the connection LBJ1 is not provided in the liquefaction separation equipment LQ, the connection LBJ1 may be provided in the line LA, the line LC, and the second distillation column T20 to supply the extractant.

[0186] In the embodiment of Figure 9, the line LB of the liquefaction separation facility LQ includes all of the connections LBJ1 and LBJ2 and the cooler 26 as liquefaction units, but it may include only one of the three, or a combination of any two of the three. Of the connections LBJ1 and LBJ2 and the cooler 26 that are not provided in the line LB, they may be provided in other components of the liquefaction separation facility LQ, i.e., the three-phase separator 23 or the gas-liquid separator 22. Also, it is possible for the line LB of the liquefaction separation facility LQ to not include any of the connections LBJ1 and LBJ2 and the cooler 26, and for the connections LBJ1 and LBJ2 and / or the cooler 26 to be provided in other components of the liquefaction separation facility LQ, i.e., the three-phase separator 23 or the gas-liquid separator 22. In addition, when the connection part LBJ1 is not provided in the liquefaction separation facility LQ, the connection part LBJ1 can be provided in the line LA, the line LC, and the second distillation column T20 in order to supply the extractant.

[0187] In the embodiment of FIG. 10 , line LB of the liquefaction separation facility LQ includes a cooler 26 and a connection LBJ1, but it may include only one of these, or neither of these. Even if line LB does not include either the cooler 26 or the connection LBJ1, the fifth distillation column T50 can still perform the liquefaction function. If the connection LBJ1 is not provided on line LB, the connection LBJ1 can be provided on another component of the liquefaction separation facility LQ, such as the fifth distillation column T50. If the connection LBJ1 is not provided on the liquefaction separation facility LQ, the connection LBJ1 can be provided on line LA, line LC, and second distillation column T20 to supply the extractant.

[0188] Furthermore, in the above embodiment, when the cooler 26 and the connection part LBJ1 are provided in the line LB, either one may be provided on the upstream side of the line LB (toward the top outlet 20t of the second distillation column), but from the viewpoint of equipment costs, it is preferable that the cooler 26 be provided on the upstream side.

[0189] Furthermore, in the above embodiment, when a connection portion LBJ2 is provided on the line LB, the connection portion LBJ2 may be located upstream or downstream of the cooler 26, or upstream or downstream of the connection portion LBJ1, but from the viewpoint of achieving sufficient liquefaction, it is preferable that the connection portion LBJ2 be located upstream of the cooler 26 and the connection portion LBJ1.

[0190] Of course, the extraction agent can be recycled without being recycled, or the extraction agent can be further purified and recycled.

[0191] In the above embodiment, the upstream second side cut line provided at the side cut outlet (not shown) instead of the top outlet 20t of the second distillation column T20 may be connected to the inlet LQi of the liquefaction separation equipment LQ.

[0192] (Method for restarting a propylene oxide purification apparatus according to one embodiment) Next, a method for restarting a propylene oxide purification apparatus according to one embodiment will be described. Here, an example using the propylene oxide purification apparatus 120 according to the third embodiment shown in FIG. 4 will be described.

[0193] (Step O) In step O, during shutdown of the propylene oxide purification apparatus 120, at least one of the streams containing propylene oxide in the upstream second drum D120, the first drum D10, and the third drum D30 is stored in at least one of the upstream second drum D120, the first drum D10, and the third drum D30, and / or in a drum other than the three drums. Examples of such a drum include an intermediate drum D130 provided between the upstream second drum D120 and the feed inlet 10i of the first distillation column T10, and / or a product drum D200 connected to the third drum D30.

[0194] The stream to be stored may be any stream containing propylene oxide as a main component (50% by mass or more), and may also contain components lighter and heavier than propylene oxide.

[0195] For example, when the propylene oxide purification apparatus is shut down, it is preferable not to discharge all of the propylene oxide-containing stream stored in the intermediate drum D130 and / or the product drum D200, but to retain at least a portion of it. Note that if the propylene oxide-containing stream stored in the intermediate drum D130 or the product drum D200 is discharged all of the time when the propylene oxide purification apparatus is shut down, the product propylene oxide may be returned to the intermediate drum D130 or the product drum D200 before start-up.

[0196] The first drum D10 and the third drum D30 may be empty at the start of startup, and are usually emptied when the apparatus is stopped for a long period of time.

[0197] (Step P) In step P, the stream containing propylene oxide stored in step O is supplied to the feed inlet 110i of the upstream first distillation column T110, and the upstream first distillation column T110 and the upstream second distillation column T120 are operated. At the start of step P, the epoxidation reactor is not in operation.

[0198] The operation of a distillation column involves heating the liquid at the bottom of the column using a heat source such as a reboiler, and the temperature of the liquid at the bottom of the column is maintained within the target temperature range for steady-state operation of each distillation column. The pressure of the distillation column is also controlled within the target range for steady-state operation.

[0199] In process P, the majority of the stream supplied to the upstream first distillation column T110 is discharged from bottom outlet 110b and supplied via line LK and feed inlet 120i to the upstream second distillation column T120. The majority of the stream supplied to the upstream second distillation column T120 is discharged from top outlet 120t and stored as a liquid in the upstream second drum D120 via line LH. The stream from the upstream second drum D120 may be refluxed to the upstream second distillation column T120.

[0200] In step P, the stream stored in the upstream second drum D120 may be supplied to the first distillation column T10, but it is preferable not to supply it to the first distillation column T10, but to reflux it entirely to the upstream first distillation column T110 via the intermediate drum D130.

[0201] In process P, most of the stream containing propylene oxide is circulated to the first distillation column T110 in the preceding step via the first distillation column T110 in the preceding step, line LK, the second distillation column T120 in the preceding step, line LH, the second drum D120 in the preceding step, and the intermediate drum D130, thereby stabilizing the temperature of the entire distillation column from the bottom to the top.

[0202] If necessary, a small amount of a top-drawn component such as propylene may be added to the first distillation column T110 in the preceding step, and a small amount of a bottom-drawn component such as cumene or 2-phenyl-propanol may be added to the second distillation column T120 in the preceding step.

[0203] (Process Q: First Aspect) In process Q, the stream containing propylene oxide stored in process O is supplied to first distillation column T10, and an extractant is supplied to second distillation column T20, thereby operating first distillation column T10, second distillation column T20, third distillation column T30, and fourth distillation column T40, and stabilizing the temperature of the entire distillation column from the bottom to the top of these distillation columns. At the start of process Q, the epoxidation reactor is not in operation. Process P and process Q may be started either first, or simultaneously.

[0204] In a first embodiment of step Q, the following steps Q1 to Q3 are further carried out, and first, the first distillation column T10 and the second distillation column T20 are separated. First, as described above, in step Q, the stream containing propylene oxide accumulated in step O is supplied to the first distillation column T10, and the first distillation column T10 is operated, whereby a stream containing propylene oxide is discharged from the top outlet 10t of the first distillation column T10 and accumulated as a liquid in the first drum D10. (Step Q1) In step Q1, the stream accumulated in the first drum D10 of the first distillation column T10 is refluxed to the first distillation column T10 without being sent to the second distillation column T20.

[0205] In addition, in step Q1, the extractant supplied to the second distillation column T20 in step Q is circulated among the second distillation column T20, the third distillation column T30, and the fourth distillation column T40 without being mixed with the stream containing propylene oxide from the first drum D10.

[0206] Specifically, the fourth distillation column T40 is started up by supplying the extractant from the extractant supply source to the feed inlet 40i of the fourth distillation column T40, and the stream stored in the fourth drum D40 of the fourth distillation column T40 is refluxed to the fourth distillation column T40. Next, the extractant discharged from the bottom outlet 40b of the fourth distillation column T40 is supplied via line LS to the extractant inlet 30e of the third distillation column T30, and the third distillation column T30 is operated. Next, the extractant discharged from the bottom outlet 30b of the third distillation column T30 is supplied via line LE to the feed inlet 20i of the second distillation column T20, and the second distillation column T20 is operated. The extractant supplied to the second distillation column T20 is discharged from the bottom outlet 20b and supplied to the feed inlet 30i of the third distillation column T30.

[0207] A portion of the extractant discharged from the bottom outlet 30b of the third distillation column T30 is supplied to the feed inlet 40i of the fourth distillation column T40 via line LT, thereby enabling the extraction agent to be circulated while maintaining its purity.

[0208] In step Q1, if necessary, the extractant-containing stream discharged from the top outlet 20t of the second distillation column T20 can be supplied to a liquefaction separation facility LQ, and then the liquid can be returned to the second distillation column T20 again.

[0209] By carrying out step Q1, the temperature of the entire distillation column from the bottom to the top of the first distillation column T10, the second distillation column T20, the third distillation column T30, and the fourth distillation column T40 can be stabilized.

[0210] (Step Q2) In step Q2, after step Q1, the propylene oxide-containing stream stored in the first drum D10 is supplied to the third distillation column T30 without passing through the second distillation column T20, and the propylene oxide-containing stream is distilled together with the extractant in the third distillation column T30. The propylene oxide-containing stream discharged from the column top outlet 30t is stored in the third drum D30 and refluxed to the third distillation column T30 via the line L9.

[0211] Specifically, methods for directly or indirectly supplying the stream from first drum D10 to third distillation column T30 include direct supply to third distillation column T30, supply to line LD, supply to line L9, supply to third drum D30, supply to line L7, and supply to line LS. In particular, it is preferable to supply the propylene oxide-containing stream from first drum D10 to third drum D30 of third distillation column T30 via line LLL, as shown in Figure 4, and then supply it to third distillation column T30 via line L9. The lines may be fixed pipes or detachable lines.

[0212] In step Q2, the circulation of the extractant between the second distillation column T20, the third distillation column T30, and the fourth distillation column T40 continues, and the supply of the extractant to the second distillation column T20 continues.

[0213] In this way, propylene oxide is supplied to the third distillation column T30, which separates propylene oxide from the extractant, bypassing the second distillation column T20, which is an extractive distillation column and in which the extractant is the main component in step Q1. This makes it possible to gradually increase the propylene oxide concentration in the second distillation column T20 by utilizing the propylene oxide in the stream returning to the second distillation column T20 via line LE, and thereby suppresses the time required for stabilization when the supply of a stream containing propylene oxide from the first drum D10 to the second distillation column T20 is started in the next step Q3.

[0214] By carrying out step Q2, the top temperatures of the first distillation column T10, the second distillation column T20, the third distillation column T30, and the fourth distillation column T40 can be stabilized.

[0215] In step Q2, if necessary, the extractant-containing stream discharged from the top of the second distillation column T20 can be supplied to a liquefaction separation facility LQ, and then the liquid can be returned to the second distillation column T20 again.

[0216] (Step Q3) In step Q3, supply of a stream containing propylene oxide from the first drum D10 via the line LF to the feed inlet 20i of the second distillation column T20 is started.

[0217] In step Q3, the circulation of the extractant between the second distillation column T20, the third distillation column T30, and the fourth distillation column T40 continues, and the supply of the extractant to the second distillation column T20 continues.

[0218] As a result, propylene oxide and the extractant are distilled in the second distillation column T20, and a stream containing propylene oxide and the extractant is supplied to the third distillation column T30 via the column bottom outlet 20b and the line LD, and in the third distillation column T30, a stream containing propylene oxide is discharged from the column top outlet 30t and stored in the third drum D30 via the line L7. At least a portion of the content of the third drum D30 may be refluxed to the third distillation column T30.

[0219] By supplying propylene oxide from the first distillation column T10 to the second distillation column T20, the concentrations of propylene oxide and the extractant in each distillation column approach steady-state concentrations. Simultaneously with the start of step Q3 or at an appropriate time thereafter, the bypass of the stream from the first drum D10 to the third distillation column T30 by step Q2 is terminated. Step Q3 allows the temperature of the entire distillation column, from the bottom to the top of each distillation column, to be stabilized.

[0220] In step Q3, if necessary, the extractant-containing stream discharged from the top of the second distillation column T20 can be supplied to a liquefaction separation facility LQ, and then the liquid can be returned to the second distillation column T20.

[0221] (Second Aspect of Step Q) In the first aspect of Step Q described above, Steps Q1, Q2, and Q3 were performed in Step Q to initially separate the first distillation column T10 and the second distillation column T20, but these do not necessarily have to be separated in Step Q. Here, differences from the first aspect of Step Q will be described.

[0222] First, in step Q, the propylene oxide-containing stream stored in step O is supplied to first distillation column T10, and an extractant is supplied to second distillation column T20, and the first distillation column T10, second distillation column T20, third distillation column T30, and fourth distillation column T40 are operated in the same manner as in the first embodiment, thereby stabilizing the temperature of the entire distillation column from the bottom to the top of these distillation columns. By operating first distillation column T10, a propylene oxide-containing stream is discharged from the top outlet 10t of first distillation column T10 and stored as a liquid in first drum D10. In the second embodiment of step Q, steps Q1 to Q3 are replaced with step Q1'. In step Q1', the propylene oxide-containing stream discharged from the top outlet 10t is supplied to second distillation column T20 via first drum D10 and line LF. In the same manner as above, the extractant is circulated among the second distillation column T20, the third distillation column T30, and the fourth distillation column T40, and is supplied to the second distillation column T20.

[0223] As a result, a stream containing propylene oxide and the extractant is distilled in the second distillation column T20, and the stream containing propylene oxide and the extractant discharged from the column bottom outlet 20b is supplied to the third distillation column T30, and in the third distillation column T30, a stream containing propylene oxide is discharged from the column top outlet 30t and stored in line L7 and the third drum D30. It is preferable to reflux a part or all of the stream from the third drum D30 to the third distillation column T30.

[0224] If necessary, the extractant-containing stream discharged from the top of the second distillation column T20 can be fed to a liquefaction separation facility LQ, and then the liquid can be returned to the second distillation column T20 again.

[0225] By supplying a portion of the extractant discharged from the bottom outlet 30b of the third distillation column T30 to the feed inlet 40i of the fourth distillation column T40, it is possible to further circulate the extractant while maintaining its purity.

[0226] In the second embodiment of this step Q, the concentrations of propylene oxide and the extractant can be brought close to a steady state, and the temperature of the entire distillation column from the bottom to the top of each distillation column can be stabilized.

[0227] By performing steps P and Q, the system of the upstream first distillation column T110 and the upstream second distillation column T120 can be separated from the systems of the first distillation column T10, the second distillation column T20, the third distillation column T30, and the fourth distillation column T40, and each distillation column can be started up in a state where it is possible to quickly stabilize the column top temperature.

[0228] (Process R) In process R, after the start of processes P and Q, a reaction between peroxide and propylene is initiated in the epoxidation reactor EPR to produce a first mixture stream containing propylene oxide and a peroxide-derived alcohol (such as 2-phenyl-2-propanol), and the first mixture stream is supplied to the feed inlet 110i of the upstream first distillation column T110 via line LN, and the stream in the upstream second drum D120 is supplied to the feed inlet 10i of the first distillation column T10. As a result, impurities in the first mixture stream are purified using a purification device, and purified propylene oxide is stored in the product drum D200.

[0229] After the start of the Q3 step or the Q' step, it is preferable to move to the R step after confirming that the purity of the propylene oxide in the third drum D30 has reached the product purity.

[0230] There is no limitation on the order in which the epoxy reaction is started, the first mixture stream is supplied to line LN, and the stream in the upstream second drum D120 is supplied to the feed inlet 10i of the first distillation column T10, and these may be performed simultaneously or at different times.

[0231] It is preferable to preliminarily introduce a solvent into the epoxidation reactor EPR used in the epoxidation step, after which propylene and peroxide are introduced into the epoxidation reactor EPR, and recovery of unreacted propylene is started using the upstream first distillation column T110.

[0232] (Operation and Effect) In the present embodiment, a stream having a higher purity of propylene oxide than the first mixture stream containing propylene oxide and a peroxide-derived alcohol (such as 2-phenyl-2-propanol) that is supplied from the epoxidation reactor EPR to the upstream first distillation column T110 in a steady state is stored in a drum in advance in step O, and this stream is supplied to the upstream first distillation column T110 to start the operation of the upstream first distillation column T110 and the upstream second distillation column T120, and is also supplied to the first distillation column T10 to start the operation of the first distillation column T10, the second distillation column T20, and the third distillation column T30, after which the reaction in the epoxidation reactor EPR is started, and the first mixture stream containing propylene oxide and the peroxide-derived alcohol (2-phenyl-2-propanol) and / or water is supplied to the upstream first distillation column T110, and as a result, the first mixture stream containing propylene oxide that is supplied from the epoxidation reactor EPR is purified.

[0233] This allows the conditions, such as temperature and pressure, in the upstream first distillation column T110, the upstream second distillation column T120, and the first distillation column T10, the second distillation column T20, and the third distillation column T30 to be stabilized to a state close to the target values ​​for steady operation, before the first mixture stream is supplied to the upstream first distillation column T110 and purification can be initiated. This means that purified propylene oxide can be obtained immediately after the first mixture stream is supplied to the upstream first distillation column T110. This reduces the time required to stabilize the operating conditions of the entire distillation column system. Furthermore, because the first mixture stream is supplied to the upstream first distillation column T110 when the distillation conditions are met, the difficulty of operation can be reduced.

[0234] In contrast, if, during start-up, the first mixture stream produced in the epoxidation reactor EPR is supplied to the upstream first distillation column T110, and operation of the upstream first distillation column T110 and the upstream second distillation column T120 is started, and then the stream discharged from the top outlet 120t of the upstream second distillation column T120 is supplied to the first distillation column T10, and operation of the first distillation column T10, the second distillation column T20, and the third distillation column T30 is started, each distillation column will start from a no-flow state and distill the streams supplied sequentially from the upstream side, and conditions such as temperature and pressure will reach their target values ​​for steady-state operation, requiring a long start-up time. Furthermore, if the first mixture stream is continuously supplied to the upstream first distillation column T110, and the operating conditions of each distillation column cannot be brought to their target values, the first mixture stream will have to be reduced or stopped, making operation difficult.

[0235] Here, storing at least one of the streams containing propylene oxide in the intermediate drum D130 and / or the product drum D200 in the O step is preferable from the following viewpoints.

[0236] That is, storing the stream in a drum provided separately from the upstream second drum D120 and third drum D30, which are often provided as reflux drums, has the advantage that the amount of liquid supplied to the first distillation column T10 can be easily kept constant even when the flow rates of the propylene oxide-containing liquid supplied from the upstream second distillation column T120, first distillation column T10, and third distillation column T30 are unstable. Another advantage is that a sufficient amount of stream can be stored.

[0237] It should be noted that this embodiment is not limited to the device shown in FIG. 4, but can be implemented in the various devices and modified modes described above.

[0238] For example, in the purification system of the sixth embodiment having a sixth distillation column T60 shown in Figure 7, in step Q, the stream containing propylene oxide accumulated in step O is first supplied to the sixth distillation column T60, and the stream accumulated in the sixth drum D60 is supplied to the first distillation column T10. It is preferable to reflux the stream from the sixth drum D60 to the sixth distillation column T60 and then supply the stream from the sixth drum D60 to the first distillation column T10, and it is also preferable to reflux the stream from the first drum D10 to the first distillation column T10.

[0239] Steps Q1 to Q3 and step Q1' are the same as those in the above-described embodiment. In the second embodiment in which steps Q1 to Q3 are performed, the system can be divided into a system including sixth distillation column T60 and first distillation column T10 and a system including second distillation column T20 and third distillation column T30.

[0240] For example, in the purification system of the seventh embodiment having the seventh distillation column T70 shown in Figure 8, in step Q, the stream containing propylene oxide accumulated in step O is first supplied to the seventh distillation column T70, and the stream discharged from the column bottom outlet 70b is supplied to the first distillation column T10. It is preferable to reflux the stream from the seventh drum D70 to the seventh distillation column T70, and then supply the stream discharged from the column bottom outlet 70b to the first distillation column T10, and it is also preferable to reflux the stream from the first drum D10 to the first distillation column T10.

[0241] Steps Q1 to Q3 and step Q1' are the same as those in the above-described embodiment. In the second embodiment in which steps Q1 to Q3 are performed, the system can be divided into a system including seventh distillation column T70 and first distillation column T10, and a system including second distillation column T20 and third distillation column T30.

[0242] 10i...Feed inlet, 10b...Tower bottom outlet, 10t...Tower top outlet, T10...First distillation column, 20i...Feed inlet, 20b...Tower bottom outlet, 20t...Tower top outlet, 23...3 phase Separator, T20...second distillation column, 30i...feed inlet, 30b...bottom outlet, 30t...column top outlet, T30...third distillation column, T40...fourth distillation column, T50...fifth distillation column, LA, LB, LC, LD, LE, LF, LX, LY...Line, 40i...Feed inlet, 40b...Column bottom outlet, 40t...Tower top outlet, T40...Fourth distillation column, 50i...Fine 50b...Tower bottom outlet, 50t...Tower top outlet, C10...First liquefaction means, C30...Third liquefaction means, C40...Fourth liquefaction means, T50...Fifth distillation column, T60...Sixth liquefaction means Distillation column (auxiliary distillation column), T70... seventh distillation column (auxiliary distillation column), T110... upstream step first distillation column, T120... upstream step second distillation column, D10... first drum, D30... third drum, D40... fourth drum, C120... upstream step second liquefaction means, D120... upstream step second drum, D130... intermediate drum, D200... product drum (downstream additional drum), LA... first side cut line, L7... third side cut line, LQ... liquefaction separation equipment, S1... source of stream containing propylene oxide, S2... source of stream containing propylene oxide and alcohol, 100, 110, 120, 130, 140, 150, 160... propylene oxide purification apparatus, EPR... epoxidation reactor.

Claims

1. A first distillation column having a feed inlet connected via line LG to a supply source of a stream containing propylene oxide, a top outlet or a side cut outlet, and a bottom outlet; either a first liquefaction means for liquefying the stream discharged from the top outlet of the first distillation column or a first side cut line connected to the side cut outlet of the first distillation column; a first drum for storing liquid supplied from the first liquefaction means or the first side cut line; a third distillation column having a feed inlet connected to the first drum via line LL, a top outlet or a side cut outlet, and a bottom outlet; either a third liquefaction means for liquefying the stream discharged from the top outlet of the third distillation column or a third side cut line connected to the side cut outlet of the third distillation column; a third drum for storing liquid discharged from the third liquefaction means or the third side cut line; and at least one of line LX and line LY, wherein the line LX is configured to supply the liquid in the first drum to the first distillation column via the feed inlet of the first distillation column, The propylene oxide purification apparatus, wherein the line LY is configured to supply the liquid in the third drum to the first distillation column through the feed inlet of the first distillation column.

2. The propylene oxide purification system according to claim 1, further comprising a product drum connected to the third drum, and the line LY connects the feed inlet of the first distillation column to the third drum via the product drum.

3. A propylene oxide purification apparatus according to claim 1 or 2, wherein the line LL is provided with a second distillation column having a feed inlet connected to the first drum of the first distillation column, a top outlet, and a bottom outlet connected to the feed inlet of the third distillation column, and the apparatus further comprises a line for directly or indirectly supplying an extractant into the second distillation column.

4. The propylene oxide purification system according to claim 3, further comprising: a liquefaction separation facility LQ that liquefies at least a portion of the stream supplied from the top outlet or side cut outlet of the second distillation column via line LB, and discharges the gas phase from the gas phase outlet and the liquid phase from the liquid phase outlet; and a line LC that connects the liquid phase outlet of the liquefaction separation facility LQ with the reflux inlet of the second distillation column.

5. The propylene oxide purification system according to claim 4, wherein the liquefaction separation facility LQ has a gas-liquid separator including the gas phase outlet, the liquid phase outlet, and a fluid inlet connected to the top outlet of the second distillation column by the line LB.

6. The propylene oxide purification apparatus according to claim 4, wherein the liquefaction separation facility LQ comprises a three-phase separator including the vapor phase outlet, the liquid phase outlet, the aqueous phase outlet, and a fluid inlet connected to the top outlet of the second distillation column by the line LB, and the apparatus further comprises a line for directly or indirectly supplying water into the three-phase separator.

7. The propylene oxide purification system according to claim 4, wherein the liquefaction separation facility LQ comprises a liquefaction means connected to the top outlet of the second distillation column via a line LB, and a fifth distillation column including a feed inlet connected to the liquefaction means, the vapor phase outlet provided at the top of the column, and the liquid phase outlet provided at the bottom of the column.

8. The propylene oxide purification apparatus according to claim 1 or 2, wherein the line LX connects the first drum and the line LG, and the line LY connects the third drum and the line LG.

9. A propylene oxide purification apparatus according to claim 1 or 2, further comprising: a first-stage second distillation column having a feed inlet connected to a supply source of a stream containing propylene oxide and peroxide-derived alcohol and / or water, a top outlet, and a bottom outlet; a first-stage second liquefaction means for liquefying the stream discharged from the top outlet of the first-stage second distillation column; and a first-stage second drum for storing the liquid discharged from the first-stage second liquefaction means, wherein the supply source of the propylene oxide-containing stream is the first-stage second drum, the line LX connects the first drum and the first-stage second drum, and the line LY connects the third drum and the first-stage second drum.

10. The propylene oxide purification apparatus according to claim 1 or 2, further comprising an intermediate drum provided in the line LG, the line LX connecting the first drum and the intermediate drum, and the line LY connecting the third drum and the intermediate drum.

11. A propylene oxide purification system according to claim 10, further comprising: a first-stage second distillation column having a feed inlet connected to a supply source of a stream containing propylene oxide and alcohol and / or water derived from a peroxide, a top outlet, and a bottom outlet; a first-stage second liquefaction means for liquefying the stream discharged from the top outlet of the first-stage second distillation column; and a first-stage second drum for storing the liquid discharged from the first-stage second liquefaction means, wherein the supply source of the stream containing propylene oxide is the first-stage second drum of the first-stage second distillation column.

12. The propylene oxide purification apparatus according to claim 1 or 2, wherein a line LG connecting the feed inlet of the first distillation column to a supply source of a stream containing propylene oxide is provided with an auxiliary distillation column for distilling the stream fed from the supply source.

13. A method for producing purified propylene oxide using the propylene oxide purification apparatus described in claim 1 or 2, comprising a step of returning the propylene oxide-containing liquid stored in at least one of the first drum and the third drum to the first distillation column via at least one of the line LX and the line LY when the purity of the propylene oxide-containing liquid stored in at least one of the first drum and the third drum falls below a predetermined threshold.

14. An epoxidation reactor for reacting peroxide with propylene to produce a first mixture stream containing propylene oxide and a peroxide-derived alcohol and / or water; a first upstream distillation column having a feed inlet to which the first mixture stream is supplied, either a top outlet or a side cut outlet to discharge a stream containing unreacted propylene, and a bottom outlet to discharge a stream containing propylene oxide and a peroxide-derived alcohol and / or water; a second upstream distillation column having a feed inlet to which a stream discharged from the bottom outlet of the first upstream distillation column is supplied, a bottom outlet to discharge a stream containing peroxide-derived alcohol and / or water, and either a top outlet or a side cut outlet to discharge a stream containing propylene oxide; either a second upstream liquefaction means for liquefying the stream discharged from the top outlet of the second upstream distillation column or a second upstream side cut line connected to the side cut outlet of the second upstream distillation column; a second upstream drum for storing a liquid discharged from the second upstream liquefaction means or the second upstream side cut line; a first distillation column having a feed inlet connected to the second drum in the preceding step, either a top outlet or a side cut outlet for discharging propylene oxide and light components, and a bottom outlet for discharging heavy components; either a first liquefaction means for liquefying a stream discharged from the top outlet of the first distillation column or a first side cut line connected to the side cut outlet of the first distillation column; a first drum for storing a liquid discharged from the first liquefaction means or the first side cut line; a second distillation column having a feed inlet connected to the first drum, either a top outlet or a side cut outlet for discharging light components and extractant, and a bottom outlet for discharging a stream containing propylene oxide and extractant; a third distillation column having a feed inlet to which a stream containing propylene oxide and extractant is supplied from the bottom outlet of the second distillation column, either a top outlet or a side cut outlet for discharging a stream containing propylene oxide, and a bottom outlet for discharging the extractant; either a third liquefaction means for liquefying the stream discharged from the top outlet of the third distillation column or a third side cut line connected to a side cut outlet of the third distillation column;and a third drum for storing a liquid discharged from the third liquefaction means or the third side cut line, the method comprising: a step O of storing at least one of the propylene oxide-containing streams in the upstream second drum, the first drum, and the third drum in at least one of the upstream second drum, the first drum, and the third drum, and / or in a drum other than the three drums of the upstream second drum, the first drum, and the third drum, during a shutdown of the propylene oxide purification apparatus; a step P of supplying the propylene oxide-containing stream stored in the step O to a feed inlet of the upstream first distillation column, and operating the upstream first distillation column and the upstream second distillation column; a step Q of supplying the propylene oxide-containing stream stored in the step O to a feed inlet of the first distillation column, and supplying an extractant to the second distillation column, and operating the first distillation column, the second distillation column, and the third distillation column; and an R step of, after the initiation of the steps P and Q, initiating a reaction of peroxide with propylene in the epoxidation reactor to produce a first mixture stream containing propylene oxide and alcohol and / or water derived from the peroxide, supplying the first mixture stream to the feed inlet of the first distillation column in the previous step, and supplying a stream in the second drum in the previous step to the feed inlet of the first distillation column.

15. The method according to claim 14, wherein in step O, at least one of the streams containing propylene oxide is stored in an intermediate drum provided between the second drum of the previous step and the feed inlet of the first distillation column, and / or in a product drum connected to the third drum.

16. The method according to claim 14 or 15, wherein step Q further comprises: step Q1, in which the stream accumulated in the first drum of the first distillation column is refluxed to the first distillation column without being sent to the second distillation column, and an extractant is circulated between the second distillation column and the third distillation column; step Q2, after step Q1, in which the stream accumulated in the first drum of the first distillation column is supplied to the third distillation column without passing through the second distillation column, and distilled in the third distillation column, and a stream from the top outlet or side cut outlet of the third distillation column is refluxed from the third drum to the third distillation column; and step Q3, after step Q2, in which the stream from the first drum of the first distillation column is supplied to the feed inlet of the second distillation column.

17. The method according to claim 16, wherein in step Q2, the stream stored in the first drum of the first distillation column is supplied to the third distillation column via a line without passing through the second distillation column.

18. The method according to claim 16, wherein in step Q2, the stream stored in the first drum of the first distillation column is supplied to the third drum of the third distillation column without passing through the second distillation column.

19. The method according to claim 16, wherein the apparatus further comprises: a fourth distillation column having a feed inlet connected to the bottom outlet of the third distillation column, a top outlet, and a bottom outlet; a fourth liquefaction means for liquefying a stream discharged from the top outlet of the fourth distillation column; and a fourth drum for storing a liquid discharged from the fourth liquefaction means; and wherein step Q further comprises the steps of supplying at least a portion of the stream containing the extractant discharged from the bottom outlet of the third distillation column to the fourth distillation column and totally refluxing the stream from the fourth drum to the fourth distillation column.

20. The method according to claim 14 or 15, further comprising providing another distillation column between the first distillation column and the previous-step second drum, the another distillation column having a feed inlet connected to the previous-step second drum, a column top outlet connected to the auxiliary drum via liquefaction means, a reflux inlet connected to the auxiliary drum, and a column bottom outlet, the auxiliary drum or the column bottom outlet being connected to the feed inlet 10i of the first distillation column, and in step Q, the propylene oxide-containing stream stored in step O is supplied to the another distillation column, and then supplied to the first distillation column via the auxiliary drum or the column bottom outlet.

21. The method according to claim 20, wherein in step O, at least one of the streams containing propylene oxide is stored in an intermediate drum provided between the second drum of the previous step and the feed inlet of the other distillation column, and / or in a product drum connected to the third drum.

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