A system and method for producing sodium methoxide

Abstract

The present invention discloses a system and method for producing sodium methoxide, belonging to the technical field of sodium methoxide preparation. The system for producing sodium methoxide includes reaction kettles D-101A / B, settling kettles V-101A to N, reactive distillation column T-101, low-pressure methanol column T-102, high-pressure methanol column T-103, and absorption column T-104. The method for producing sodium methoxide using the system for producing sodium methoxide includes the following steps: using anhydrous methanol and solid caustic soda as raw materials, and obtaining sodium methoxide through reactive distillation in the system; in the system, the methanol gas phase has no phase change and is recycled as a non-phase change gas phase, and the low-pressure methanol column T-102 and the high-pressure methanol column T-103 are used as partial heat coupling devices. The present invention overcomes the defects of the prior art, greatly reduces energy consumption, has remarkable practicability and economic benefits, and has a broad application prospect.

Description

Technical Field

[0001] The present invention belongs to the technical field of sodium methoxide preparation, and particularly relates to a system and method for producing sodium methoxide. Background Art

[0002] Currently, with the rapid development of China's manufacturing industry, all industries attach great importance to the active layout of their entire industrial chains. Among them, sodium methoxide can be used in the production of sulfonamides; it can be used as an alkaline condensing agent and catalyst in organic synthesis, for the synthesis of spices, dyes, etc., and is a raw material for vitamins B1, A, and sulfadiazine; it can be used as a raw material for pharmaceuticals and pesticides, and is an important raw material for the synthesis of drugs such as sulfamidine, sulfamethoxazole, and sulfonamide synergists, occupying an extremely important position in the chemical industry.

[0003] In the critical stage of increasing international environmental pressure, high energy costs, and increasing initiative in industry transformation, market competition will become increasingly fierce, and the industry will enter a low-profit era. Cost reduction and efficiency improvement will become one of the decisive factors in competition. Adopting double-effect heat coupling to produce sodium methoxide can achieve the purpose of energy conservation and consumption reduction, which is of great significance. Summary of the Invention

[0004] In view of this, the present invention provides a system and method for producing sodium methoxide, which uses anhydrous methanol and sodium hydroxide (solid caustic soda) as raw materials, and adopts a method of methanol gas-phase without phase change and partial device heat coupling to produce sodium methoxide products.

[0005] To achieve the above object, the present invention proposes the following technical solutions:

[0006] A system for producing sodium methoxide, according to the liquid-phase material flow direction, the system for producing sodium methoxide sequentially includes a reaction kettle D-101A / B, sedimentation kettles V-101A to N, a reactive distillation column T-101, a low-pressure methanol column T-102, a high-pressure methanol column T-103, and an absorption column T-104; the sedimentation kettles V-101A to N discharge alkali sludge at the bottom of the kettle; the tail gas in the system enters the absorption column T-104 for absorption; the high-pressure methanol column T-103 and the low-pressure methanol column T-102 are in complete heat coupling operation, and the gas phase at the top of the high-pressure methanol column T-103 provides heat source for the low-pressure methanol column T-102, and the condenser of the high-pressure methanol column T-103 is also the reboiler of the low-pressure methanol column T-102.

[0007] Further, the reactive distillation column T-101 can also be divided into a reactive stripping column T-101A and an atmospheric pressure methanol column T-101B.

[0008] Further, a feed preheater 1 and a feed preheater 2 are also provided before the reactive distillation column T-101.

[0009] Further, an air cooler or a water cooler is also provided for the reactive distillation column T-101.

[0010] The present invention also provides a method for producing sodium methoxide by using the system for producing sodium methoxide as described above, comprising the following steps:

[0011] Using anhydrous methanol and solid sodium hydroxide flakes as raw materials, sodium methoxide is obtained through reactive distillation in the system; wherein the high-pressure methanol column and the low-pressure methanol column are in completely thermally coupled operation, and the methanol gas phase in the system is a non-phase-change gas cycle, and the methanol gas phase does not need to be condensed and directly provides most of the heat for the reactive distillation column.

[0012] Further, the specific steps of the method are as follows:

[0013] 1) Pass anhydrous methanol and solid sodium hydroxide flakes into the reaction kettle D-101A / B for dissolution to obtain a sodium hydroxide methanol solution; 2) Pass the sodium hydroxide methanol solution into the settling kettle V-101A to N for static settling to obtain the settled sodium hydroxide methanol solution; 3) The settled sodium hydroxide methanol solution enters the first feed preheater and the second feed preheater in sequence and then enters the reactive distillation column T-101. The bottom of the column is fed with a circulating anhydrous methanol gas phase. The anhydrous methanol is taken out from the top of the column and sent to the top of the low-pressure methanol column T-102. The water-containing methanol is taken out from the middle (i.e., the side line take-off port) of the column and sent to the bottom of the low-pressure methanol column T-102. A 30 wt% sodium methoxide methanol solution is taken out from the bottom of the reactive distillation column T-101. This product can be dehydrated by a target dryer to obtain a sodium methoxide solid product with a purity of more than 99.5%; 4) The anhydrous methanol gas taken out from the top of the low-pressure methanol column T-102 enters the bottom of the reactive distillation column T-101 as the raw material of the anhydrous methanol gas phase. The water-containing methanol taken out from the bottom of the column is preheated by the high-pressure methanol column T-103 feed preheater and then sent into the high-pressure methanol column T-103 to recover anhydrous methanol from the high-pressure methanol column T-103; 5) The anhydrous methanol gas phase at the top of the high-pressure methanol column T-103 enters the condenser (the condenser is also the reboiler of the low-pressure methanol column T-102 and provides heat for the low-pressure methanol column T-102). After condensation, the material is sent to the top of the high-pressure methanol column T-103 and the top of the low-pressure methanol column T-102 respectively. The wastewater discharged from the bottom of the high-pressure methanol column T-103 is heat-exchanged and cooled with the feed sodium hydroxide methanol solution and then sent out of the device to provide heat for the raw material sodium hydroxide methanol solution and reduce energy loss; 6) The bottom of the absorption column T-104 is fed with the condensed tail gas in the system, and the top of the column is fed with process water for absorption. The water-containing methanol solution in the bottom of the absorption column T-104 after absorption enters the high-pressure methanol column T-103 to further recover anhydrous methanol; the purified tail gas is discharged from the top of the absorption column T-104.

[0014] The above process flow can also be evolved as follows:

[0015] Evolution process one:

[0016] The main deformation of this process flow is that the side-stream product of the reactive distillation column T-101 is first sent to the bottom of the high-pressure methanol column T-103, and wastewater is discharged from the bottom of the low-pressure methanol column T-102. Specifically:

[0017] 1) Anhydrous methanol and solid caustic soda are introduced into the reactors D-101A / B for dissolution to obtain a caustic methanol solution; 2) The caustic methanol solution is introduced into the settlers V-101A to N for static settlement to remove sludge, and the settled caustic methanol solution is obtained; 3) The settled caustic methanol solution enters the feed preheater I and feed preheater II in sequence, and then enters the reactive distillation column T-101. Anhydrous methanol gas phase is introduced into the bottom of the column. A 30 wt% sodium methoxide methanol solution is obtained from the bottom of the reactive distillation column T-101. This product can be dehydrated by a target dryer to obtain a sodium methoxide solid product with a purity of over 99.5%; The gas phase at the top of the reactive distillation column T-101 is condensed, and part of it is refluxed and part is sent to the top of the low-pressure methanol column T-102; The product taken from the middle of the reactive distillation column T-101 is sent to the bottom of the high-pressure methanol column T-103; 4) The material at the bottom of the high-pressure methanol column T-103 is sent to the middle of the low-pressure methanol column T-102. The gas phase of the high-pressure methanol column T-103 is condensed by a condenser and then sent to the top of the high-pressure methanol column T-103 and the top of the low-pressure methanol column T-102 respectively; 5) The gas phase at the top of the low-pressure methanol column T-102 enters the bottom of the reactive distillation column T-101 as the methanol gas phase raw material, and the wastewater discharged from the bottom of the low-pressure methanol column T-102 is sent out of the device; 6) The tail gas in the system enters the bottom of the absorption column T-104 for absorption treatment with process water. After absorption, a dilute methanol aqueous solution is obtained and sent to the low-pressure methanol column T-102 for methanol recovery, and then the wastewater is discharged (the dilute methanol solution at the bottom of the absorption column T-104 preferentially enters the low-pressure methanol column T-102 for methanol recovery. Methanol is recovered and wastewater is discharged simultaneously. The wastewater can be used as absorption water).

[0018] Evolved process two:

[0019] The main deformation of this process flow is that the reactive distillation column T-101 is divided into two parts, namely the reactive stripping column T-101A and the atmospheric pressure methanol column T-101B. The specific steps are as follows:

[0020] 1) Anhydrous methanol and solid caustic soda are introduced into the reaction kettle D-101A / B for dissolution to obtain a caustic soda solution; 2) The caustic soda solution is introduced into the settling kettle V-101A to N for static settling to obtain the settled caustic soda solution; 3) The settled caustic soda solution enters the top of the reaction stripping tower T-101A. Anhydrous methanol gas phase is introduced into the bottom of the reaction stripping tower T-101A. A 30 wt% sodium methoxide methanol solution is withdrawn from the bottom of the tower. This product can be dehydrated by a target dryer to obtain a sodium methoxide solid product with a purity of over 99.5%; The gas phase at the top of the reaction stripping tower T-101A directly enters the bottom of the atmospheric tower T-101B. After the gas phase at the top of the atmospheric tower T-101B is condensed, a part of it is refluxed and a part is sent to the top of the low-pressure methanol tower T-102; The material withdrawn from the bottom of the atmospheric tower T-101B is sent to the bottom of the low-pressure methanol tower T-102; 4) The liquid in the bottom of the low-pressure methanol tower T-102 is preheated in the feed preheater of the high-pressure methanol tower T-103 and then enters the middle of the high-pressure methanol tower T-103; 5) The gas phase at the top of the high-pressure methanol tower T-103 is condensed by a condenser and then sent to the top of the high-pressure methanol tower T-103 and the top of the low-pressure methanol tower T-102 respectively to recover anhydrous methanol from the middle of the high-pressure methanol tower T-103. Waste water is discharged from the bottom of the high-pressure methanol tower T-103; 6) The tail gas in the system is sent to the bottom of the absorption tower T-104 and is absorbed and treated with process water. The dilute methanol aqueous solution obtained after absorption is sent to the high-pressure methanol tower T-103 to recover anhydrous methanol and then the waste water is discharged.

[0021] Evolved Process Three:

[0022] The main deformation of this process flow is that the reactive distillation column T-101 is divided into two, namely the reaction stripping tower T-101A and the atmospheric methanol tower T-101B. The material withdrawn from the bottom of the atmospheric tower T-101B is sent to the bottom of the high-pressure methanol tower T-103, and waste water is discharged from the bottom of the low-pressure methanol tower T-102. The specific steps are as follows:

[0023] 1) Anhydrous methanol and solid sodium hydroxide flakes are introduced into the reaction kettle D-101A / B for dissolution to obtain a sodium methoxide solution; 2) The sodium methoxide solution is introduced into the settling kettle V-101A to N for static settling to obtain the settled sodium methoxide solution; 3) The settled sodium methoxide solution enters the top of the reaction stripping column T-101A. Anhydrous methanol gas phase is introduced into the kettle of the reaction stripping column T-101A. A 30 wt% sodium methoxide methanol solution is withdrawn from the kettle. This product can be dehydrated by a target dryer to obtain a sodium methoxide solid product with a purity of over 99.5%; The gas phase at the top of the reaction stripping column T-101A directly enters the kettle of the atmospheric column T-101B. The gas phase at the top of the atmospheric column T-101B is condensed and sent to the top of the low-pressure methanol column T-102; The material withdrawn from the kettle of the atmospheric column T-101B is sent to the kettle of the high-pressure methanol column T-103; 4) The material in the kettle of the high-pressure methanol column T-103 is sent to the middle of the low-pressure methanol column T-102. The gas phase at the top of the high-pressure methanol column T-103 is condensed by a condenser and sent to the top of the high-pressure methanol column T-103 and the top of the low-pressure methanol column T-102 respectively; 5) The anhydrous methanol gas phase at the top of the low-pressure methanol column T-102 enters the kettle of the stripping column T-101A, and wastewater is discharged from the kettle of the low-pressure methanol column T-102; 6) The tail gas in the system is sent to the kettle of the absorption column T-104 and is absorbed and treated with process water. After absorption, a dilute methanol aqueous solution is obtained and sent to the low-pressure methanol column T-102 to recover methanol and then the wastewater is discharged.

[0024] According to the process method provided by the present invention, the heat sources used for the reboiler of the reactive distillation column T-101 and the reboiler of the high-pressure methanol column T-103 can be fresh steam or heat transfer oil.

[0025] According to the process method provided by the present invention, the main condenser of the reactive distillation column T-101 and the tail condenser of the reactive distillation column T-101 can also be water coolers; The cooling media used can be circulating water, low-temperature water, chilled water, or other cooling media such as low-temperature materials inside the system.

[0026] Furthermore, the operating conditions of each column are as follows:

[0027] The operating pressure range of the reaction kettle D-101A / B is 100 - 150 kPaA;

[0028] The operating pressure range of the settling kettle V-101A to N is 100 - 120 kPaA;

[0029] The operating pressure range of the top of the reactive distillation column T-101 is 100 - 200 kPaA;

[0030] The operating pressure range of the top of the low-pressure methanol column T-102 is 220 - 320 kPaA;

[0031] The operating pressure range of the top of the high-pressure methanol column T-103 is 320 - 580 kPaA;

[0032] The operating pressure range at the top of the absorption tower T-104 is 100 - 130 kPaA.

[0033] Furthermore, the conditions for each tower are as follows:

[0034] The operating pressure range of the reactors D-101A / B is 101 - 110 kPaA, and the operating temperature is 20 - 80 °C;

[0035] The operating pressure range of the settling tanks V-101A - N is 101 - 110 kPaA, and the operating temperature is 20 - 60 °C;

[0036] The operating pressure range at the top of the reactive distillation column T-101 is 100 - 120 kPaA, the operating temperature at the top is 70 - 80 °C, and the operating temperature at the bottom of the column is 85 - 105 °C;

[0037] The operating pressure at the top of the low-pressure methanol column T-102 is 220 - 320 kPaA, the operating temperature at the top is 80 - 100 °C, and the operating temperature at the bottom of the column is 85 - 105 °C;

[0038] The operating pressure at the top of the high-pressure methanol column T-103 is 320 - 580 kPaA, the operating temperature at the top is 95 - 115 °C, and the operating temperature at the bottom of the column is 140 - 160 °C;

[0039] The operating pressure at the top of the absorption tower T-104 is 100 - 105 kPaA, the operating temperature at the top is 20 - 40 °C, and the operating temperature at the bottom of the column is 25 - 60 °C.

[0040] According to the process method provided by the present invention, the energy-saving method is as follows:

[0041] 1) The raw material of the caustic soda solution is preheated in two stages with steam condensate and the wastewater at the bottom of the high-pressure methanol column T-103 respectively, reducing the consumption of heat sources and also reducing the consumption of circulating water.

[0042] 2) The high-pressure methanol column T-103 and the low-pressure methanol column T-102 are in a completely thermally coupled operation. The gas phase at the top of the high-pressure methanol column T-103 provides heat for the low-pressure methanol column T-102, and the condenser of the high-pressure methanol column T-103 is also the reboiler of the low-pressure methanol column T-102. In this process, there is only one heat stream in the reboiler at the bottom of the high-pressure methanol column T-103, saving equipment investment and also greatly saving the consumption of circulating water and system thermal energy.

[0043] 3) The methanol gas phase in the system is a non-phase-change gas phase cycle. The methanol gas phase from the top of the low-pressure methanol column T-102 does not need to be condensed and is directly introduced into the bottom of the reactive distillation column T-101, providing most of the heat for the reactive distillation column T-101. Saving equipment investment and also greatly saving the consumption of circulating water and system thermal energy.

[0044] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0045] The present invention provides a process for producing sodium methoxide using methanol and sodium hydroxide (solid caustic soda) as raw materials. It can be used to produce sodium methoxide products. In the device, the gas phase at the top of the high-pressure methanol tower T-103 provides heat source for the low-pressure methanol tower T-102, and the methanol gas phase in the system is a non-phase-change gas cycle. The methanol gas phase from the top of the low-pressure methanol tower T-102 does not need to be condensed and is directly introduced into the bottom of the reactive distillation tower T-101, providing most of the heat for the reactive distillation tower T-101. Some heat exchangers in the process are omitted, saving equipment investment and also greatly saving the consumption of circulating water and system heat energy. The present invention overcomes the defects of the prior art, greatly reduces energy consumption, has remarkable practicability and economic benefits, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0047] Figure 1 It is the process flow diagram of Embodiment 1;

[0048] Figure 2 It is the process flow diagram of Embodiment 2;

[0049] Figure 3 It is the process flow diagram of Embodiment 3;

[0050] Figure 4 It is the process flow diagram of Embodiment 4. DETAILED DESCRIPTION OF THE INVENTION

[0051] Now, various exemplary embodiments of the present invention will be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention.

[0052] It should be understood that the terms described in the present invention are only for describing specific implementation modes and are not used to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.

[0053] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Although only preferred methods and materials are described in this invention, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of this invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0054] Without departing from the scope or spirit of this invention, various improvements and changes can be made to the specific embodiments of the description of this invention, which are obvious to those skilled in the art. Other embodiments obtained from the description of this invention are obvious to those skilled in the art. The description and examples of this application are merely exemplary.

[0055] Regarding the use of "comprising", "including", "having", "containing", etc. herein, they are all open-ended terms, meaning including but not limited to.

[0056] Example 1 (see the process flow chart in Figure 1 )

[0057] 1) Anhydrous methanol and solid sodium hydroxide are added to the reaction kettle D-101 (there are two reaction kettles A and B in the reaction kettle D-101, which are used alternately to ensure the continuous operation of the subsequent reactive distillation section) in a mass ratio of 4:1 for dissolution (the operating pressure is 101 - 110 kPaA, the operating temperature is 20 - 80 °C, and it takes about 2 hours until the sodium hydroxide is completely dissolved) to obtain a methyl alkali solution;

[0058] 2) The methyl alkali solution is introduced into the settling kettle V-101 (A - N represent N settling kettles, and the number of settling kettles is determined according to production needs. Since the discharge of alkali sludge from the settling kettle is intermittent and sufficient time is required for sedimentation, several more settling kettles need to be set up, at least 4 - 6. In this example, 6 settling kettles are set up) for static settling to remove the alkali sludge (the operating pressure is 101 - 110 kPaA, the operating temperature is 20 - 60 °C, and the sedimentation time is at least 24 hours until the alkali sludge is completely sedimented) to obtain the settled methyl alkali solution;

[0059] 3) The settled sodium hydroxide solution enters the feed preheater 1 and feed preheater 2 in sequence for preheating (preheated to 40 - 80 °C and 80 - 120 °C respectively), and then enters the middle of the reactive distillation column T-101 (the top operating pressure is 100 - 120 kPaA, the top operating temperature is 60 - 70 °C, the bottom operating pressure is 120 - 140 kPaA, and the bottom operating temperature is 85 - 105 °C). The anhydrous methanol gas phase in circulation is introduced into the bottom of the reactive distillation column T-101, and the mass ratio of the introduced amount to the feed amount of the sodium hydroxide solution in the reactive distillation column T-101 is (4 - 4.9):1. The anhydrous methanol is taken out from the top of the reactive distillation column T-101 and sent to the top of the low-pressure methanol column T-102, and the methanol containing water is taken out from the middle (i.e., the side draw outlet) and sent to the bottom of the low-pressure methanol column T-102. The methanol sodium methanol solution with a purity of 30 wt% is taken out from the bottom of the reactive distillation column T-101. This product can be dehydrated by a target dryer to obtain a sodium methoxide solid product with a purity of more than 99.5%;

[0060] 4) The anhydrous methanol gas phase is taken out from the top of the low-pressure methanol column T-102 (the top operating pressure is 220 - 320 kPaA, the top operating temperature is 80 - 100 °C, the bottom operating pressure is 220 - 320 kPaA, and the bottom operating temperature is 85 - 105 °C) and enters the bottom of the reactive distillation column T-101 as the raw material of the anhydrous methanol gas phase. The ratio of the amount of the anhydrous methanol gas phase to the feed amount of the sodium hydroxide solution in the reactive distillation column T-101 is approximately (4 - 4.9):1. The methanol containing water taken out from the bottom is preheated by the feed preheater of the high-pressure methanol column T-103 and then sent into the middle of the high-pressure methanol column T-103;

[0061] 5) The anhydrous methanol gas phase at the top of the high-pressure methanol column T-103 (the top operating pressure is 320 - 580 kPaA, the top operating temperature is 95 - 115 °C, the bottom operating pressure is 330 - 590 kPaA, and the bottom operating temperature is 140 - 160 °C) enters the condenser (the condenser is also the reboiler of the low-pressure methanol column T-102, providing heat source for the low-pressure methanol column T-102). After condensation, the materials are respectively sent to the top of the high-pressure methanol column T-103 and the top of the low-pressure methanol column T-102. The wastewater discharged from the bottom of the high-pressure methanol column T-103 is exchanged heat with the feed sodium hydroxide solution for cooling and then sent out of the device, providing heat source for the raw material sodium hydroxide solution and reducing energy loss;

[0062] 6) The tail gas condensed in the system is introduced into the bottom of the absorption column T-104 (the top operating pressure is 100 - 105 kPaA, the top operating temperature is 20 - 40 °C, the bottom operating pressure is 105 - 110 kPaA, and the bottom operating temperature is 25 - 60 °C), and process water is introduced into the top for absorption. The methanol solution containing water in the bottom of the absorption column T-104 after absorption enters the middle of the high-pressure methanol column T-103 for further recovery of methanol and then discharges the wastewater; the purified tail gas is discharged from the top of the absorption column T-104.

[0063] Example 2 (for the process flow chart, see Figure 2 )

[0064] 1) Anhydrous methanol and solid sodium hydroxide flakes are fed into reactor D-101 (there are two reactors A and B in reactor D-101, which are used alternately to ensure the continuous operation of the subsequent reactive distillation section) according to a mass ratio of 4:1 for dissolution (the operating pressure is 101 - 110 kPaA, the operating temperature is 20 - 80 °C, and it takes about 2 hours until the sodium hydroxide flakes are completely dissolved) to obtain a sodium methoxide solution;

[0065] 2) The sodium methoxide solution is fed into sedimentation tank V-101 (A - N represent N sedimentation tanks, and the number of sedimentation tanks is determined according to production needs. Since the discharge of alkali sludge from the sedimentation tank is intermittent and sedimentation requires sufficient time, several more sedimentation tanks need to be set up to ensure the continuous operation of reactive distillation, at least 4 - 6. In this example, 6 sedimentation tanks are set up) for static sedimentation to remove alkali sludge (the operating pressure is 101 - 110 kPaA, the operating temperature is 20 - 60 °C, and the sedimentation time is at least 24 hours until the alkali sludge is completely sedimented) to obtain the sedimented sodium methoxide solution;

[0066] 3) The sedimented sodium methoxide solution is preheated in feed preheater 1 and feed preheater 2 (preheated to 40 - 80 °C and 80 - 120 °C respectively) and then enters the middle of reactive distillation column T-101 (the top operating pressure is 100 - 120 kPaA, the top operating temperature is 60 - 70 °C, the bottom operating pressure is 120 - 140 kPaA, and the bottom operating temperature is 85 - 105 °C). Anhydrous methanol gas phase is fed into the bottom of the column, and the mass ratio of the feeding amount to the feeding amount of the sodium methoxide solution in reactive distillation column T-101 is (4 - 4.9):1. A sodium methoxide methanol solution with a purity of 30 wt% is obtained from the bottom of reactive distillation column T-101. This product can be dehydrated by a target dryer to obtain a sodium methoxide solid product with a purity of more than 99.5%;

[0067] After the gas phase at the top of reactive distillation column T-101 is condensed, part of it is refluxed and part is sent to the top of low-pressure methanol column T-102; the water-containing methanol is withdrawn from the middle part (i.e., the side draw outlet) of reactive distillation column T-101 and sent to the bottom of high-pressure methanol column T-103, and the withdrawal amount is in a mass ratio of (1.7 - 2.6):1 to the sodium methoxide solution in reactive distillation column T-101;

[0068] 4) The bottom material of high-pressure methanol column T-103 (the top operating pressure is 320 - 580 kPaA, the top operating temperature is 95 - 115 °C, the bottom operating pressure is 330 - 590 kPaA, and the bottom operating temperature is 140 - 160 °C) is sent to the middle part of low-pressure methanol column T-102. The gas phase of high-pressure methanol column T-103 is condensed by a condenser and then sent to the top of high-pressure methanol column T-103 and the top of low-pressure methanol column T-102 respectively;

[0069] 5) The gas phase at the top of the low-pressure methanol tower T-102 (with a top operating pressure of 220 - 320 kPaA, a top operating temperature of 80 - 100 °C, a bottom operating pressure of 220 - 320 kPaA, and a bottom operating temperature of 85 - 105 °C) enters the bottom of the reactive distillation tower T-101 as the gas-phase raw material of anhydrous methanol. The mass ratio of the amount of anhydrous methanol to the feed amount of the methylamine solution in the reactive distillation tower T-101 is (4 - 4.9):1. The wastewater discharged from the bottom of the low-pressure methanol tower T-102 is sent out of the device.

[0070] 6) The tail gas in the system enters the absorption tower T-104 (with a top operating pressure of 100 - 105 kPaA, a top operating temperature of 20 - 40 °C, a bottom operating pressure of 105 - 110 kPaA, and a bottom operating temperature of 25 - 60 °C). The bottom of the tower uses process water for absorption treatment. After absorption, the obtained dilute methanol aqueous solution is sent to the low-pressure methanol tower T-102 to recover methanol and then the wastewater is discharged.

[0071] Example 3 (The process flow diagram is shown in Figure 3 )

[0072] 1) Anhydrous methanol and solid caustic soda are introduced into the reaction kettle D-101 (there are two reaction kettles A and B in the reaction kettle D-101, which are used alternately to ensure the continuous operation of the subsequent reactive distillation section) according to a mass ratio of 4:1 for dissolution (the operating pressure is 101 - 110 kPaA, the operating temperature is 20 - 80 °C, and it takes about 2 hours until the caustic soda is completely dissolved) to obtain the methylamine solution.

[0073] 2) The methylamine solution is introduced into the settling kettle V-101 (A - N represent N settling kettles, and the number of settling kettles is determined according to production needs. Since the discharge of alkali sludge from the settling kettle is intermittent and sufficient time is required for sedimentation, in order to ensure the continuous operation of the reactive distillation, several more settling kettles need to be set, at least 4 - 6. In this example, 6 settling kettles are set) for static settling to remove the alkali sludge (the operating pressure is 101 - 110 kPaA, the operating temperature is 20 - 60 °C, and the sedimentation time is at least 24 hours until the alkali sludge is completely sedimented) to obtain the settled methylamine solution.

[0074] 3) The settled sodium methylate solution enters the feed preheater 1 and feed preheater 2 in sequence for preheating (preheated to 40 - 80 °C and 80 - 120 °C respectively), and then enters the top of the reaction stripper T - 101A (the top operating pressure is 100 - 120 kPaA, the top operating temperature is 80 - 90 °C, the bottom operating pressure is 120 - 140 kPaA, and the bottom operating temperature is 85 - 105 °C). Anhydrous methanol gas phase is introduced into the bottom of the reaction stripper T - 101A, and the mass ratio of the introduced amount to the sodium methylate solution feed amount of the reactive distillation column T - 101A is (4 - 4.9):1. The product taken from the bottom is a sodium methoxide methanol solution with a purity of 30 wt%. This product can be dehydrated by a target dryer to obtain a sodium methoxide solid product with a purity of over 99.5%;

[0075] The gas phase at the top of the reaction stripper T - 101A directly enters the bottom of the atmospheric column T - 101B (the top operating pressure is 100 - 120 kPaA, the top operating temperature is 60 - 70 °C, the bottom operating pressure is 100 - 120 kPaA, and the bottom operating temperature is 70 - 80 °C). After the gas phase at the top of the atmospheric column T - 101B is condensed, part of it is refluxed and part is sent to the top of the low - pressure methanol column T - 102; The aqueous methanol solution taken from the bottom of the atmospheric column T - 101B is sent to the bottom of the low - pressure methanol column T - 102, and the taken - out amount and the mass ratio of the sodium methylate solution feed amount of the reaction stripper T - 101A is (1.7 - 2.6):1;

[0076] 4) The bottom liquid of the low - pressure methanol column T - 102 (the top operating pressure is 220 - 320 kPaA, the top operating temperature is 80 - 100 °C, the bottom operating pressure is 220 - 320 kPaA, and the bottom operating temperature is 85 - 105 °C) is preheated in the feed preheater of the high - pressure methanol column T - 103 (preheated to 115 - 135 °C) and then enters the middle part of the high - pressure methanol column T - 103;

[0077] 5) The gas phase at the top of the high - pressure methanol column T - 103 (the top operating pressure is 320 - 580 kPaA, the top operating temperature is 95 - 115 °C, the bottom operating pressure is 330 - 590 kPaA, and the bottom operating temperature is 140 - 160 °C) is condensed by a condenser and then sent to the top of the high - pressure methanol column T - 103 and the top of the low - pressure methanol column T - 102 respectively. The mass ratio of the amount of anhydrous methanol to the sodium methylate solution feed amount of the reactive distillation column T - 101A is (0.7 - 1.2):1. Waste water is discharged from the bottom of the high - pressure methanol column T - 103;

[0078] 6) The tail gas in the system is sent to the bottom of the absorption tower T-104 (the top operating pressure is 100-105 kPaA, the top operating temperature is 20-40 °C, the bottom operating pressure is 105-110 kPaA, and the bottom operating temperature is 25-60 °C). It is absorbed using process water. After absorption, the dilute methanol aqueous solution is sent to the high-pressure methanol tower T-103 to recover methanol and then the wastewater is discharged. The mass ratio of the amount of anhydrous methanol to the mass of the sodium methoxide solution fed to the reactive distillation column T-101A is (0.8-1.2):60.

[0079] Example 4 (see the process flow diagram in Figure 4 )

[0080] 1) Anhydrous methanol and solid sodium hydroxide flakes are fed into the reaction kettle D-101 (there are two reaction kettles A and B in the reaction kettle D-101, which are used alternately to ensure the continuous operation of the subsequent reactive distillation section) in a mass ratio of 4:1 for dissolution (the operating pressure is 101-110 kPaA, the operating temperature is 20-80 °C, and it takes about 2 hours until the sodium hydroxide flakes are completely dissolved) to obtain a sodium methoxide solution.

[0081] 2) The sodium methoxide solution is fed into the settling kettle V-101 (A to N represent N settling kettles, and the number of settling kettles is determined according to production needs. Since the discharge of alkali sludge from the settling kettle is intermittent and sufficient settling time is required, several more, at least 4-6, are needed to ensure the continuous operation of the reactive distillation. In this example, 6 settling kettles are set) for static settling to remove the alkali sludge (the operating pressure is 101-110 kPaA, the operating temperature is 20-60 °C, and the settling time is at least 24 hours until the alkali sludge is completely settled) to obtain the settled sodium methoxide solution.

[0082] 3) The settled sodium methoxide solution is preheated in the feed preheater I and the feed preheater II in sequence (preheated to 40-80 °C and 80-120 °C respectively) and then enters the top of the reactive stripping tower T-101A (the top operating pressure is 100-120 kPaA, the top operating temperature is 80-90 °C, the bottom operating pressure is 120-140 kPaA, and the bottom operating temperature is 85-105 °C). Anhydrous methanol gas phase is fed into the bottom of the reactive stripping tower T-101A, and the feeding amount is in a mass ratio of (4-4.9):1 to the mass of the sodium methoxide solution fed to the reactive distillation column T-101A. The product withdrawn from the bottom is a 30 wt% sodium methoxide methanol solution, which can be dried by a target dryer to remove the volume and obtain a sodium methoxide solid product with a purity of more than 99.5%.

[0083] The gas phase at the top of the reaction stripper column T-101A directly enters the bottom of the atmospheric column T-101B. The gas phase at the top of the atmospheric column T-101B (with an operating pressure at the top of 100 - 120 kPaA, an operating temperature at the top of 60 - 70 °C, an operating pressure at the bottom of 100 - 120 kPaA, and an operating temperature at the bottom of 70 - 80 °C) is condensed and sent to the top of the low-pressure methanol column T-102; the methanol aqueous solution withdrawn from the bottom of the atmospheric column T-101B is sent to the bottom of the high-pressure methanol column T-103, and the mass ratio of the withdrawal amount to the mass of the methylamine solution feed to the reaction stripper column T-101A is (1.7 - 2.6):1;

[0084] 4) The material at the bottom of the high-pressure methanol column T-103 (with an operating pressure at the top of 320 - 580 kPaA, an operating temperature at the top of 95 - 115 °C, an operating pressure at the bottom of 330 - 590 kPaA, and an operating temperature at the bottom of 140 - 160 °C) is sent to the middle of the low-pressure methanol column T-102 (with an operating pressure at the top of 220 - 320 kPaA, an operating temperature at the top of 80 - 100 °C, an operating pressure at the bottom of 220 - 320 kPaA, and an operating temperature at the bottom of 85 - 105 °C). The gas phase at the top of the high-pressure methanol column T-103 is condensed by a condenser and then sent to the top of the high-pressure methanol column T-103 and the top of the low-pressure methanol column T-102 respectively;

[0085] 5) The anhydrous methanol gas phase at the top of the low-pressure methanol column T-102 enters the bottom of the reactive distillation column T-101. The mass ratio of the amount of the anhydrous methanol gas phase to the mass of the methylamine solution feed to the reaction stripper column T-101A is (4 - 4.9):1. Waste water is discharged from the bottom of the low-pressure methanol column T-102;

[0086] 6) The tail gas in the system is sent to the bottom of the absorption column T-104 (with an operating pressure at the top of 100 - 105 kPaA, an operating temperature at the top of 20 - 40 °C, an operating pressure at the bottom of 105 - 110 kPaA, and an operating temperature at the bottom of 25 - 60 °C) for absorption treatment with process water. After absorption, the obtained dilute methanol aqueous solution is sent to the low-pressure methanol column T-102 to recover methanol and then the waste water is discharged. The mass ratio of the amount of anhydrous methanol to the mass of the methylamine solution feed to the reactive distillation column T-101A is (0.8 - 1.2):60.

[0087] In the system of the present invention, heat exchange between hot materials and cold materials, and condensate of low-pressure steam can preheat any tower in the system or their permutations and combinations. The above various heat exchange methods and their combinations only provide a process method for the heat exchange network for producing sodium methoxide of the present invention, rather than any limitation on the spirit of the present invention. Those skilled in the relevant art can make appropriate modifications, changes and combinations according to the method provided by the present invention to implement this technology. It should be particularly noted that all these similar modifications, changes and recombinations to the process flow provided by the present invention are obvious to those skilled in the art and are regarded as within the spirit, scope and content of the present invention.

[0088] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for producing sodium methoxide using a system for producing sodium methoxide, characterized in that, The method for producing sodium methoxide comprises the following steps: anhydrous methanol and solid caustic soda as raw materials are dissolved and reacted in a reaction kettle to obtain a methoxide solution; the methoxide solution is settled in a settling kettle to obtain the settled methoxide solution, and the alkali sludge is directly discharged; the settled methoxide solution is preheated and then sent to the middle part of a reactive distillation column, and anhydrous methanol gas phase taken from the top of a low-pressure methanol column is introduced into the kettle of the column; the gas phase at the top of the reactive distillation column is condensed by circulating water and low-temperature water, and a part of the condensed gas is used as reflux, and the other part enters the top of the low-pressure methanol column, and a sodium methoxide-methanol solution product is obtained at the kettle of the reactive distillation column; the material taken from the middle of the reactive distillation column enters the bottom of the low-pressure methanol column; the gaseous methanol material taken from the top of the low-pressure methanol column is directly introduced into the bottom of the reactive distillation column, and the material at the kettle of the low-pressure methanol column enters the middle part of a high-pressure methanol column after being preheated by a high-pressure methanol column feed preheater; a part of the material taken from the top of the high-pressure methanol column is returned to the top of the high-pressure methanol column as reflux, and the other part is taken out to the top of the low-pressure methanol column, and the waste water discharged from the kettle of the high-pressure methanol column is taken out of the device after being heat-exchanged and cooled with the incoming methoxide solution raw material feed; The system for producing sodium methoxide, in the order of the liquid-phase material flow direction, successively comprises a reaction kettle, a settling kettle, a reactive distillation column, a low-pressure methanol column and a high-pressure methanol column; alkali sludge is discharged from the bottom of the settling kettle; the tail gas in the system enters an absorption column for absorption; the high-pressure methanol column and the low-pressure methanol column are in a fully thermally coupled operation, the gas phase at the top of the high-pressure methanol column provides heat source for the low-pressure methanol column, and the condenser of the high-pressure methanol column is also the reboiler of the low-pressure methanol column; A feed preheater I and a feed preheater II are also provided before the reactive distillation column.

2. The method according to claim 1, characterized in that, The operating conditions of each column are as follows: The operating pressure range of the reaction kettle is 100-150 kPaA; The operating pressure range of the settling kettle is 100-120 kPaA; The operating pressure range at the top of the reactive distillation column is 100-200 kPaA; The operating pressure range at the top of the low-pressure methanol column is 220-320 kPaA; The operating pressure range at the top of the high-pressure methanol column is 320-580 kPaA; The operating pressure range at the top of the absorption column is 100-130 kPaA.

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