A method for recovering and refining waste liquid from propylene oxide process

Abstract

This invention discloses a method for recovering and refining waste liquid from a propylene oxide (PO) process, belonging to the field of chemical technology. The method includes: dehydrating and heating the PO process waste liquid, then sending it to a waste liquid coarse separation tower for distillation to obtain a mixture of light components and a mixture of heavy components; completely condensing and separating the light component mixture; the resulting oil phase component entering an ethylbenzene refining tower for distillation to obtain ethylbenzene product and a propylene oxide-acetone mixture; the heavy component mixture entering a waste liquid de-heavy treatment tower to obtain a high-boiling-point mixture and an AMS-cumene-phenol mixture; the AMS-cumene-phenol mixture entering a cumene product tower for refining to obtain cumene product gas and an AMS-phenol mixture; and the AMS-phenol mixture entering an AMS product tower for refining to obtain an AMS product and an AMS-phenol mixed gas. This invention reduces emissions of waste gas, wastewater, and solid waste, and the return of cumene as a raw material to the system reduces material consumption and significantly improves the economic efficiency of the plant.

Description

Technical Field

[0001] This invention belongs to the field of chemical technology, specifically relating to a method for recovering and refining waste liquid from a propylene oxide process, and more particularly to a method for recovering waste liquid from a propylene oxide process and refining cumene, ethylbenzene, and α-methylstyrene. Background Technology

[0002] Propylene oxide (PO) plays an important role in chemical synthesis and is currently the third largest propylene derivative. In existing technologies, propylene oxide is mainly used to produce polyether polyols and propylene glycol; among which, polyether polyols are important raw materials for the production of polyurethane foam, insulation materials, elastomers, adhesives, and coatings, and the number of downstream products derived from them is vast and their applications are wide-ranging.

[0003] Due to the unique nature of the process, propylene oxide production units generate process waste liquid. This waste liquid mainly consists of cumene, ethylbenzene, dimethylbenzyl alcohol (DMPC), phenol, α-methylstyrene (AMS), propylene oxide, acetone, water, and high-boiling-point substances. Material and energy consumption are core indicators for all process routes in propylene oxide production, determining the future direction of the process. Therefore, providing a method for recovering and refining propylene oxide process waste liquid, capable of recovering and refining cumene, ethylbenzene, and AMS from the waste liquid, reducing emissions of these three pollutants, lowering material consumption, and significantly improving the economic efficiency of the unit, has become a pressing issue for those skilled in the art. Summary of the Invention

[0004] The purpose of this invention is to provide a method for recovering and refining propylene oxide process waste liquid, maximizing the recovery and refining of cumene from the propylene oxide process waste liquid to obtain the products cumene, ethylbenzene, and AMS. To achieve the above objective, the technical solution adopted by this invention is as follows:

[0005] This invention provides a method for recovering and refining waste liquid from a propylene oxide process, comprising the following steps:

[0006] Step 1. Dehydration and heating: The waste liquid from the propylene oxide process is dehydrated and heated to dehydrate dimethylbenzyl alcohol in the waste liquid to produce α-methylstyrene and water;

[0007] Step 2. Coarse separation: The material after dehydration and heating reaction is sent to a waste liquid coarse separation tower for distillation and separation to obtain a mixture of light components and a mixture of heavy components.

[0008] Step 3. Oil-water phase separation and ethylbenzene distillation: After the light component mixture is completely condensed in a condenser, oil-water phase separation is performed; the oil phase component enters the ethylbenzene refining tower for distillation and separation to obtain ethylbenzene product and propylene oxide-acetone mixture, respectively.

[0009] Step 4. Deweighting treatment: The heavy component mixture enters the waste liquid deweighting tower, and after distillation deweighting treatment, high-boiling-point mixture and AMS-cumene-phenol mixture are obtained respectively;

[0010] Step 5. Cumene distillation: The AMS-cumene-phenol mixture is purified in the cumene product tower to obtain cumene product gas and AMS-phenol mixture, respectively.

[0011] Step 6. AMS distillation: The AMS-phenol mixture is purified in the AMS product column to obtain AMS product and AMS-phenol mixed gas respectively;

[0012] There is no specific order between steps 3 and steps 4-6.

[0013] In some embodiments of the present invention, in step 3, the oil phase after oil-water separation is divided into two streams, one of which enters the ethylbenzene refining tower for refining, and the other is returned to the waste liquid coarse separation tower;

[0014] The aqueous phase after oil and water separation is sent to a wastewater treatment system for further treatment.

[0015] In some embodiments of the present invention, in step 3, the propylene oxide-acetone mixture obtained by distillation separation in the ethylbenzene refining tower is completely condensed in a condenser and then stored in the reflux tank at the top of the ethylbenzene refining tower.

[0016] Preferably, the discharge from the reflux tank at the top of the ethylbenzene refining tower is divided into two streams. One stream is cooled by a cooler and then stored in a propylene oxide-acetone waste liquid buffer tank as propylene oxide-acetone waste liquid; the other stream is returned to the ethylbenzene refining tower.

[0017] In some embodiments of the present invention, in step 3, the ethylbenzene product obtained by distillation and separation in the ethylbenzene refining tower is cooled and then stored in an ethylbenzene buffer tank.

[0018] Preferably, the ethylbenzene product obtained by distillation separation in the ethylbenzene refining tower is divided into two streams. One stream is cooled and stored in an ethylbenzene buffer tank; the other stream is reboiled and returned to the ethylbenzene refining tower.

[0019] In some embodiments of the present invention, the heavy component mixture obtained by distillation separation in the waste liquid coarse separator in step 2 is discharged from the waste liquid coarse separator and divided into two streams. One stream is returned to the waste liquid coarse separator after reboiling, and the other stream enters the waste liquid deweighting tower for distillation deweighting treatment.

[0020] Preferably, in step 4, the high-boiling-point mixture obtained after the deweighting treatment is cooled and then sent to a high-boiling-point buffer tank for caching.

[0021] Preferably, after the high-boiling-point mixture is obtained after the deweighting treatment, it is discharged from the waste liquid deweighting tower and divided into two streams. One stream is returned to the waste liquid deweighting tower after reboiling, and the other stream is sent to the high-boiling-point buffer tank for caching after cooling.

[0022] In some embodiments of the present invention, in step 4, the AMS-cumene-phenol mixture obtained after deweighting treatment is completely condensed and then stored in the buffer tank at the top of the waste liquid deweighting tower. The discharge from the buffer tank at the top of the waste liquid deweighting tower is divided into two streams: one stream enters the cumene product tower for refining, and the other stream returns to the waste liquid deweighting tower.

[0023] In some embodiments of the present invention, in step 5, the cumene product gas obtained by refining in the cumene product tower is completely condensed in the top condenser of the cumene product tower and then stored in the top reflux tank of the cumene product tower.

[0024] Preferably, the discharge from the reflux tank at the top of the cumene product tower is divided into two streams: one stream returns to the cumene product tower, and the other stream is cooled and then sent to the cumene product tank for storage.

[0025] In some embodiments of the present invention, in step 5, the AMS-phenol mixture obtained by purification in the cumene product tower is divided into two streams after being discharged from the cumene product tower. One stream enters the AMS product tower for distillation and purification, while the other stream is returned to the cumene product tower after reboiling.

[0026] In some embodiments of the present invention, in step 6, the AMS-phenol mixed gas obtained by distillation in the AMS product tower is completely condensed in the top condenser of the AMS product tower and then stored in the top reflux tank of the AMS product tower. The discharge from the top reflux tank of the AMS product tower is divided into two streams, one of which is cooled and sent to the AMS-phenol waste liquid buffer tank, and the other is returned to the AMS product tower.

[0027] In some embodiments of the present invention, in step 6, the AMS product obtained by distillation in the AMS product column is discharged from the AMS product column and divided into two streams. One stream is cooled and sent to the AMS product buffer tank; the other stream is reboiled and returned to the AMS product column.

[0028] In some embodiments of the present invention, the operating pressure of the waste liquid coarse separation tower is -0.1 to 0 MPaG, the operating pressure of the ethylbenzene refining tower is 0 to 0.1 MPaG, the operating pressure of the waste liquid deweighting tower is -0.1 to 0 MPaG, the operating pressure of the cumene product tower is -0.1 to 0 MPaG, and the operating pressure of the AMS product tower is -0.1 to 0 MPaG.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] This invention is scientifically designed, ingeniously conceived, and simple in method. It involves the distillation and separation of waste liquid from a propylene oxide plant, maximizing the recovery and purification of cumene from the process waste liquid to obtain cumene, ethylbenzene, and AMS products. This reduces emissions of waste gas, wastewater, and solid waste, and cumene is returned to the system as a raw material to reduce material consumption and significantly improve the plant's economic efficiency. Using this method, the recovery rates of cumene and ethylbenzene are greater than 99%, and the recovery rate of AMS is greater than 90%. The recovered products have a purity greater than 99.32 wt% for cumene, greater than 99.94 wt% for ethylbenzene, and greater than 99.50 wt% for AMS. Attached Figure Description

[0031] Appendix Figure 1 This is a schematic diagram of the process flow for the recovery and purification of waste liquid from the propylene oxide process of the present invention.

[0032] The names corresponding to the reference numerals in the attached figures are as follows:

[0033] a- Waste liquid coarse separation tower, b- Ethylbenzene refining tower, c- Waste liquid de-weighting tower, d- Cumene product tower, e- AMS product tower, f- DMPC dehydration heater, g- Waste liquid coarse separation tower bottom reboiler, h- Waste liquid coarse separation tower top condenser, i- Ethylbenzene refining tower bottom reboiler, j- Ethylbenzene refining tower bottom cooler, k- Ethylbenzene refining tower top condenser, l- Ethylbenzene refining tower top cooler, m- Waste liquid de-weighting tower bottom reboiler, n- Waste liquid de-weighting tower bottom cooler, o- Waste liquid de-weighting tower Top condenser of the tower, p-reboiler at the bottom of the cumene product tower, q-top condenser of the cumene product tower, r-top cooler of the cumene product tower, s-bottom reboiler of the AMS product tower, t-bottom cooler of the AMS product tower, u-top condenser of the AMS product tower, v-top cooler of the AMS product tower, w-top phase separation tank at the top of the waste liquid coarse separation tower, x-reflux tank of the ethylbenzene refining tower, y-reflux tank of the waste liquid de-heavy removal tower, z-reflux tank of the cumene product tower, aa-reflux tank of the AMS product tower. Detailed Implementation

[0034] To make the purpose, technical solution, and advantages of this invention patent clearer, the following description is provided in conjunction with the appendix. Figure 1 The present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the scope of the present invention.

[0035] A method for recovering and refining waste liquid from a propylene oxide process includes the following steps:

[0036] Step 1. Dehydration and heating: The waste liquid from the propylene oxide process is dehydrated and heated to dehydrate dimethylbenzyl alcohol in the waste liquid to produce α-methylstyrene and water;

[0037] Step 2. Coarse separation: The material after dehydration and heating reaction is sent to a waste liquid coarse separation tower for distillation and separation to obtain a mixture of light components and a mixture of heavy components.

[0038] Step 3. Oil-water phase separation and ethylbenzene distillation: After the light component mixture is completely condensed in a condenser, oil-water phase separation is performed; the oil phase component enters the ethylbenzene refining tower for distillation and separation to obtain ethylbenzene product and propylene oxide-acetone mixture, respectively.

[0039] Step 4. Deweighting treatment: The heavy component mixture enters the waste liquid deweighting tower, and after distillation deweighting treatment, high-boiling-point mixture and AMS-cumene-phenol mixture are obtained respectively;

[0040] Step 5. Cumene distillation: The AMS-cumene-phenol mixture is purified in the cumene product tower to obtain cumene product gas and AMS-phenol mixture, respectively.

[0041] Step 6. AMS distillation: The AMS-phenol mixture is purified in the AMS product column to obtain AMS product and AMS-phenol mixed gas respectively;

[0042] There is no specific order between steps 3 and steps 4-6.

[0043] In step 3, the oil phase after oil-water separation is divided into two streams, one of which enters the ethylbenzene refining tower for refining, and the other is returned to the waste liquid coarse separation tower.

[0044] The aqueous phase after oil and water separation is sent to a wastewater treatment system for further treatment.

[0045] In step 3, the propylene oxide-acetone mixture obtained by distillation separation in the ethylbenzene refining tower is completely condensed in a condenser and then stored in the reflux tank at the top of the ethylbenzene refining tower.

[0046] Preferably, the discharge from the reflux tank at the top of the ethylbenzene refining tower is divided into two streams. One stream is cooled by a cooler and then stored in a propylene oxide-acetone waste liquid buffer tank as propylene oxide-acetone waste liquid; the other stream is returned to the ethylbenzene refining tower.

[0047] In step 3, the ethylbenzene product obtained by distillation and separation in the ethylbenzene refining tower is cooled and then stored in an ethylbenzene buffer tank.

[0048] Preferably, the ethylbenzene product obtained by distillation separation in the ethylbenzene refining tower is divided into two streams. One stream is cooled and stored in an ethylbenzene buffer tank; the other stream is reboiled and returned to the ethylbenzene refining tower.

[0049] The heavy component mixture obtained by distillation separation in the waste liquid coarse separator in step 2 is discharged from the waste liquid coarse separator and divided into two streams. One stream is returned to the waste liquid coarse separator after reboiling, and the other stream enters the waste liquid deweighting tower for distillation deweighting treatment.

[0050] Preferably, in step 4, the high-boiling-point mixture obtained after the deweighting treatment is cooled and then sent to a high-boiling-point buffer tank for caching.

[0051] Preferably, after the high-boiling-point mixture is obtained after the deweighting treatment, it is discharged from the waste liquid deweighting tower and divided into two streams. One stream is returned to the waste liquid deweighting tower after reboiling, and the other stream is sent to the high-boiling-point buffer tank for caching after cooling.

[0052] In step 4, the AMS-cumene-phenol mixture obtained after deweighting treatment is completely condensed and then stored in the buffer tank at the top of the waste liquid deweighting tower. The discharge from the buffer tank at the top of the waste liquid deweighting tower is divided into two streams: one stream enters the cumene product tower for refining, and the other stream returns to the waste liquid deweighting tower.

[0053] In step 5, the cumene product gas obtained by refining in the cumene product tower is completely condensed in the top condenser of the cumene product tower and then stored in the top reflux tank of the cumene product tower.

[0054] Preferably, the discharge from the reflux tank at the top of the cumene product tower is divided into two streams: one stream returns to the cumene product tower, and the other stream is cooled and then sent to the cumene product tank for storage.

[0055] In step 5, the AMS-phenol mixture obtained by purification in the cumene product tower is divided into two streams after being discharged from the cumene product tower. One stream enters the AMS product tower for distillation and purification, while the other stream is returned to the cumene product tower after reboiling.

[0056] In step 6, the AMS-phenol mixture obtained by distillation in the AMS product tower is completely condensed in the top condenser of the AMS product tower and then stored in the top reflux tank of the AMS product tower. The discharge from the top reflux tank of the AMS product tower is divided into two streams. One stream is cooled and sent to the AMS-phenol waste liquid buffer tank, and the other stream is returned to the AMS product tower.

[0057] In step 6, the AMS product obtained by distillation in the AMS product tower is discharged from the AMS product tower and divided into two streams. One stream is cooled and sent to the AMS product buffer tank; the other stream is reboiled and returned to the AMS product tower.

[0058] Example 1

[0059] As attached Figure 1 As shown in the figure, this embodiment discloses the method for recycling and refining propylene oxide process waste liquid of the present invention, specifically: Step 1. Dehydration and heating: 40°C propylene oxide process waste liquid 1 (flow rate: 1700 kg / h) from the propylene oxide unit is sent to the DMPC dehydration heater f for dehydration and heating, so that 95% of the dimethylbenzyl alcohol (DMPC) in the waste liquid is dehydrated to generate α-methylstyrene (AMS) and water.

[0060] Step 2. Coarse separation: The 155°C stream 2 after dehydration and heating reaction is sent to the middle of the waste liquid coarse separation tower a for distillation separation to obtain light component mixture stream 5 and heavy component mixture stream; wherein the composition of light component mixture stream 5 is PO, acetone, ethylbenzene and water.

[0061] Step 3. Oil-water phase separation and ethylbenzene distillation: The light component mixture stream 5 is discharged from the top of the waste liquid roughing tower a and then enters the condenser h at the top of the waste liquid roughing tower for total condensation. The gas-liquid two-phase stream 6 after total condensation enters the left side of the baffle of the phase separation tank w at the top of the waste liquid roughing tower for oil-water phase separation; thus obtaining the oil phase PO-acetone-ethylbenzene mixture and water.

[0062] The aqueous phase stream 10 (74.8 kg / h) separated from the phase separation tank w at the top of the waste liquid coarse separation tower is sent to the wastewater treatment system.

[0063] The 23.4℃ oil phase discharge stream 7, separated from the phase separation tank w at the top of the waste liquid roughing tower, is divided into two streams: an oil phase recirculation stream 8 and an oil phase output stream 9. The oil phase recirculation stream 8 is returned to the top of the waste liquid roughing tower a, while the oil phase output stream 9 (276 kg / h) enters the middle of the ethylbenzene refining tower b for distillation and separation, yielding ethylbenzene product and a PO-acetone mixture, respectively.

[0064] The ethylbenzene product obtained from the distillation separation in ethylbenzene refining column b is discharged from the bottom of column b and divided into two streams: ethylbenzene product recirculation stream 11 and ethylbenzene product outflow stream 12. Epoxy benzene product recirculation stream 11, at 148.9℃, enters the reboiler i at the bottom of the ethylbenzene refining column for reboiling and then returns to ethylbenzene refining column b. Epoxy benzene product outflow stream 12 (233.2 kg / h) enters the cooler j at the bottom of the ethylbenzene refining column for cooling. The cooled Epoxy benzene product outflow stream 13, at 40℃, is then sent to the ethylbenzene product buffer tank.

[0065] The PO-acetone mixed stream 14, obtained from the distillation separation in ethylbenzene refining column b, is discharged from the top of column b and then enters the condenser k at the top of column b for total condensation. The PO-acetone mixed stream 15, after total condensation at 45.4℃, enters the reflux tank x of column b for storage. The PO-acetone mixed discharge stream 16 from the reflux tank x is divided into two streams: a PO-acetone mixed circulating stream 17 and a PO-acetone mixed outflow stream 18. The PO-acetone mixed circulating stream 17 is refluxed to the top of column b, while the PO-acetone mixed outflow stream 18 (42.8 kg / h) enters the cooler l at the top of column b for cooling. The cooled PO-acetone mixed outflow stream 19, at 10℃, is sent to the PO-acetone waste buffer tank.

[0066] Step 4. Heavy component removal treatment: The heavy component mixture obtained from the distillation separation in the waste liquid coarse separator a in Step 2 is discharged from the bottom of the waste liquid coarse separator a and divided into two streams. One stream is the heavy component recirculation stream 3, and the other is the heavy component outflow stream 4. The heavy component recirculation stream 3, at 131.7℃, enters the reboiler g at the bottom of the waste liquid coarse separator for reboiling and then returns to the waste liquid coarse separator a. The heavy component outflow stream 4 (1349.2 kg / h) enters the middle of the waste liquid heavy component removal tower c for distillation and heavy component removal. After heavy component removal treatment, a high-boiling-point mixture and an AMS-cumene-phenol mixture are obtained, respectively.

[0067] The high-boiling-point mixture obtained after deweighting treatment is discharged from the bottom of the waste liquid deweighting tower c and splits into two streams. One stream is a high-boiling-point mixture-phenol-DMPC circulating stream 20, and the other stream is a high-boiling-point mixture-phenol-DMPC outflow stream 21. The high-boiling-point mixture-phenol-DMPC circulating stream 20, at 88.3℃, enters the reboiler m at the bottom of the waste liquid deweighting tower for reboiling and then returns to the waste liquid deweighting tower c. The high-boiling-point mixture-phenol-DMPC outflow stream 21 (705 kg / h) enters the cooler n at the bottom of the waste liquid deweighting tower for cooling. The cooled high-boiling-point mixture-phenol-DMPC outflow stream 22, at 50℃, is sent to the high-boiling-point buffer tank.

[0068] After the deweighting treatment, the AMS-cumene-phenol mixed stream 23 is discharged from the top of the waste liquid deweighting tower c and then enters the top condenser o of the waste liquid deweighting tower for total condensation. The condensed AMS-cumene-phenol mixed stream 24 at 50.7℃ enters the waste liquid deweighting tower reflux tank y for storage. The AMS-cumene-phenol mixed discharge stream 25 from the waste liquid deweighting tower reflux tank y is divided into two streams: the AMS-cumene-phenol mixed circulating stream 26 and the AMS-cumene-phenol mixed outflow stream 27. The AMS-cumene-phenol mixed circulating stream 26 is refluxed to the top of the waste liquid deweighting tower c, while the AMS-cumene-phenol mixed outflow stream 27 (644.2 kg / h) enters the cumene product tower d for distillation.

[0069] Step 5. Cumene distillation: The AMS-cumene-phenol mixed outflow stream 27 is fed into the cumene product tower d for distillation and purification, yielding cumene product and AMS-phenol mixture respectively.

[0070] The cumene product stream 30, obtained from the distillation and purification of cumene product column d, is discharged from the top of column d and then enters the cumene product column top condenser q for total condensation. The cumene product stream 31, at 110.9℃ after total condensation, enters the cumene product column reflux tank z for storage. The cumene product discharge stream 32 from the cumene product column reflux tank z is divided into two streams: a cumene product circulation stream 33 and a cumene product collection stream 34. The cumene product circulation stream 33 is returned to the top of cumene product column d, while the cumene product collection stream 34 (300 kg / h) enters the cumene product column top cooler r for cooling. After cooling to 40℃, the cumene product collection stream 35 is sent to the cumene product tank. Stream 35 contains cumene product with a purity of 99.32 wt%.

[0071] The AMS-phenol mixed stream obtained by distillation and purification in cumene product column d is discharged from the bottom of cumene product column d and splits into two streams: AMS-phenol mixed recirculation stream 28 and AMS-phenol mixed outflow stream 29. AMS-phenol mixed recirculation stream 28, at 127.6℃, enters the reboiler p at the bottom of the cumene product column for reboiling and then returns to cumene product column d; AMS-phenol mixed outflow stream 29 (344.2 kg / h) is sent to the middle section of AMS product column e.

[0072] Step 6. AMS distillation: The AMS-phenol mixed outflow stream 29 (344.2 kg / h) is fed into the middle of the AMS product tower e for distillation and purification to obtain AMS-phenol mixed gas and AMS product respectively.

[0073] The AMS-phenol mixture 39 obtained by distillation in AMS product column e is discharged from the top of AMS product column e and then enters the top condenser u of AMS product column for total condensation. The AMS-phenol mixture stream 40 with a temperature of 109.6℃ after total condensation enters the reflux tank aa of AMS product column for storage.

[0074] The AMS-phenol mixed discharge stream 41 of the AMS product tower reflux tank aa is divided into two streams: the AMS-phenol mixed circulation stream 42 and the AMS-phenol mixed outflow stream 43. The AMS-phenol mixed circulation stream 42 is refluxed to the top of the AMS product tower e, while the AMS-phenol mixed outflow stream 43 (35 kg / h) enters the AMS product tower top cooler v for cooling. After cooling to 50°C, the AMS-phenol mixed outflow stream 44 is sent to the AMS-phenol waste buffer tank.

[0075] The AMS product obtained from distillation in AMS product column e is discharged from the bottom of the column and divided into two streams: AMS product recirculation stream 36 and AMS product outflow stream 37. AMS product recirculation stream 36, at 117.6℃, enters the reboiler s at the bottom of the AMS product column for reboiling and then returns to AMS product column e. AMS product outflow stream 37 (309.2 kg / h) enters the cooler t at the bottom of the AMS product column for cooling. After cooling to 40℃, AMS product outflow stream 38 is sent to the AMS product buffer tank. Stream 38 is AMS product with a purity of 99.5 wt%.

[0076] In this embodiment, the feed rate of the propylene oxide process waste liquid is 1700 kg / h, wherein the mass fraction of high-boiling-point substances is 25.33 wt%, the mass fraction of DMPC is 23.92 wt%, the mass fraction of cumene is 17.7 wt%, the mass fraction of phenol is 14.91 wt%, the mass fraction of ethylbenzene is 13.74 wt%, the mass fraction of PO is 2.3 wt%, the mass fraction of water is 1 wt%, the mass fraction of acetone is 0.6 wt%, and the mass fraction of AMS is 0.5 wt%.

[0077] In this embodiment, the operating pressure of the waste liquid coarse separation tower a is -0.068 MPaG, the top temperature is 92.7℃, and the bottom temperature is 137.9℃.

[0078] In this embodiment, the operating pressure of the ethylbenzene refining tower b is 0.03 MPaG, the top temperature is 50.3°C, and the bottom temperature is 149°C.

[0079] In this embodiment, the operating pressure of the waste liquid deweighting tower c is -0.099 MPaG, the top temperature of the tower is 52.2℃, and the bottom temperature of the tower is 95.8℃.

[0080] In this embodiment, the operating pressure of the cumene product tower d is -0.071 MPaG, the top temperature is 111°C, and the bottom temperature is 127.8°C.

[0081] In this embodiment, the operating pressure of the AMS product tower e is -0.081 MPaG, the top temperature is 110°C, and the bottom temperature is 117.8°C.

[0082] In this embodiment, the recovery rate of cumene is greater than 99%, and the purity of cumene is greater than 99.32 wt%. The recovery rate of ethylbenzene is greater than 99%, and the purity of ethylbenzene is greater than 99.94 wt%. The recovery rate of AMS is greater than 90%, and the purity of AMS is greater than 99.50 wt%.

[0083] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for recovering and refining waste liquid from a propylene oxide process, characterized in that, Includes the following steps: Step 1. Dehydration and heating: The waste liquid from the propylene oxide process is dehydrated and heated to dehydrate dimethylbenzyl alcohol in the waste liquid to produce α-methylstyrene and water; Step 2. Coarse separation: The material after dehydration and heating reaction is sent to the waste liquid coarse separation tower for distillation and separation to obtain a mixture of light components and a mixture of heavy components. The operating pressure of the waste liquid coarse separation tower is -0.1~0 MPaG. Step 3. Oil-water phase separation and ethylbenzene distillation: After the light component mixture is completely condensed in a condenser, it undergoes oil-water phase separation; the oil phase component enters the ethylbenzene refining tower for distillation and separation to obtain ethylbenzene product and propylene oxide-acetone mixture, respectively. Step 4. Deweighting treatment: The heavy component mixture enters the waste liquid deweighting tower, and after distillation deweighting treatment, high-boiling-point mixture and AMS-cumene-phenol mixture are obtained respectively; Step 5. Cumene distillation: The AMS-cumene-phenol mixture is purified in the cumene product tower to obtain cumene product gas and AMS-phenol mixture, respectively. Step 6. AMS distillation: The AMS-phenol mixture is purified in the AMS product column to obtain AMS product and AMS-phenol mixed gas respectively; There is no specific order between steps 3 and steps 4-6.

2. The method for recovering and refining propylene oxide process waste liquid according to claim 1, characterized in that, In step 3, the oil phase after oil-water separation is divided into two streams, one of which enters the ethylbenzene refining tower for refining, and the other is returned to the waste liquid coarse separation tower. The aqueous phase after oil and water separation is sent to a wastewater treatment system for further treatment.

3. A method for recovering and refining propylene oxide process waste liquid according to claim 1 or 2, characterized in that, In step 3, the propylene oxide-acetone mixture obtained by distillation separation in the ethylbenzene refining tower is completely condensed in a condenser and then stored in the reflux tank at the top of the ethylbenzene refining tower.

4. The method for recovering and refining propylene oxide process waste liquid according to claim 3, characterized in that, The discharge from the reflux tank at the top of the ethylbenzene refining tower is divided into two streams. One stream is cooled by a cooler and then stored in the propylene oxide-acetone waste liquid buffer tank as propylene oxide-acetone waste liquid; the other stream is returned to the ethylbenzene refining tower.

5. A method for recovering and refining propylene oxide process waste liquid according to claim 1 or 2, characterized in that, In step 3, the ethylbenzene product obtained by distillation and separation in the ethylbenzene refining tower is cooled and then stored in an ethylbenzene buffer tank.

6. A method for recovering and refining propylene oxide process waste liquid according to claim 1 or 2, characterized in that, In step 3, the ethylbenzene product obtained by distillation and separation in the ethylbenzene refining tower is divided into two streams. One stream is cooled and stored in an ethylbenzene buffer tank; the other stream is reboiled and returned to the ethylbenzene refining tower.

7. The method for recovering and refining propylene oxide process waste liquid according to claim 1, characterized in that, The heavy component mixture obtained by distillation separation in the waste liquid coarse separator in step 2 is discharged from the waste liquid coarse separator and divided into two streams. One stream is returned to the waste liquid coarse separator after reboiling, while the other stream enters the waste liquid deweighting tower for distillation deweighting treatment.

8. The method for recovering and refining propylene oxide process waste liquid according to claim 1, characterized in that, In step 4, the high-boiling-point mixture obtained after the deweighting treatment is cooled and then sent to a high-boiling-point buffer tank for caching.

9. The method for recovering and refining propylene oxide process waste liquid according to claim 1, characterized in that, After the deweighting process, the high-boiling-point mixture is discharged from the waste liquid deweighting tower and split into two streams. One stream is returned to the waste liquid deweighting tower after reboiling, and the other stream is sent to the high-boiling-point buffer tank for caching after cooling.

10. The method for recovering and refining propylene oxide process waste liquid according to claim 1, characterized in that, In step 4, the AMS-cumene-phenol mixture obtained after deweighting treatment is completely condensed and then stored in the buffer tank at the top of the waste liquid deweighting tower. The discharge from the buffer tank at the top of the waste liquid deweighting tower is divided into two streams: one stream enters the cumene product tower for refining, and the other stream returns to the waste liquid deweighting tower.

11. The method for recovering and refining propylene oxide process waste liquid according to claim 10, characterized in that, In step 5, the cumene product gas obtained by refining in the cumene product tower is completely condensed in the top condenser of the cumene product tower and then stored in the top reflux tank of the cumene product tower.

12. The method for recovering and refining propylene oxide process waste liquid according to claim 11, characterized in that, The discharge from the reflux tank at the top of the cumene product tower is divided into two streams: one stream returns to the cumene product tower, and the other stream is cooled and sent to the cumene product tank for storage.

13. A method for recovering and refining propylene oxide process waste liquid according to claim 11, characterized in that, In step 5, the AMS-phenol mixture obtained by purification in the cumene product tower is divided into two streams after being discharged from the cumene product tower. One stream enters the AMS product tower for distillation and purification, while the other stream is returned to the cumene product tower after reboiling.

14. A method for recovering and refining propylene oxide process waste liquid according to claim 1, characterized in that, In step 6, the AMS-phenol mixture obtained by distillation in the AMS product tower is completely condensed in the top condenser of the AMS product tower and then stored in the top reflux tank of the AMS product tower. The discharge from the top reflux tank of the AMS product tower is divided into two streams. One stream is cooled and sent to the AMS-phenol waste liquid buffer tank, and the other stream is returned to the AMS product tower.

15. The method for recovering and refining propylene oxide process waste liquid according to claim 14, characterized in that, In step 6, the AMS product obtained by distillation in the AMS product tower is discharged from the AMS product tower and divided into two streams. One stream is cooled and sent to the AMS product buffer tank; the other stream is reboiled and returned to the AMS product tower.

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