Method and system for continuously recovering and refining triethylamine in glyphosate production

Abstract

The invention provides a method for continuously recovering and refining triethylamine in glyphosate production, which comprises the following steps: adding alkali to neutralize glyphosate acid mother liquor, and feeding a crude triethylamine solution replaced by reaction layering into a layering large tank for layering; upper-layer liquid obtained by layering continuously overflows to a triethylamine refining preheater to be heated and then enters a triethylamine refining tower, and lower-layer alkali mother liquor is heated by a triethylamine mother liquor preheater and then continuously conveyed to a triethylamine mother liquor rectifying tower; tower top gas phases of the triethylamine refining tower and the triethylamine mother liquor rectifying tower are condensed, enter a reflux tank at the same time and return to respective tower tops; a tower kettle discharged material of the triethylamine refining tower is used as a heat source of a triethylamine refining preheater to preheat upper-layer liquid, and a tower kettle discharged material of the triethylamine mother liquor rectifying tower is used as a heat source of a triethylamine mother liquor preheater to preheat lower-layer alkali mother liquor; the liquid phase at the upper part of the reflux tank flows back to the top of the triethylamine refining tower, and the liquid phase at the lower part flows back to the top of the triethylamine mother liquor rectifying tower, so that material coupling and negative feedback regulation of double-tower rectification are realized. The method is continuous, efficient, safe and environment-friendly.

Description

Technical Field

[0001] The invention belongs to the field of glyphosate production, and particularly relates to a method and system for continuously recovering and refining triethylamine in glyphosate production. Background Art

[0002] Currently, most domestic glyphosate production processes using the glycine process use formaldehyde, glycine, and dimethyl phosphite as raw materials, methanol as solvent, and triethylamine as catalyst to prepare a synthetic solution. Hydrochloric acid is then added for acidolysis and hydrolysis, and the solvent is removed by heating to produce a slurry containing glyphosate. This slurry is stirred, cooled, and crystallized. Alkali is added to adjust the pH to precipitate glyphosate crystals. Solid-liquid separation is then performed to produce glyphosate-containing wet powder and glyphosate acid mother liquor. The glyphosate wet powder is then dried to produce the technical product. The glyphosate acid mother liquor is typically treated by adding liquid caustic soda to regenerate the triethylamine salt into triethylamine. After standing and separating, the upper triethylamine layer and the lower alkali mother liquor layer are formed. The upper triethylamine layer is dehydrated to produce triethylamine, with a main content of over 99.0%, which can be recycled as a catalyst in the glyphosate synthesis process. The lower alkali mother liquor is distilled in a triethylamine mother liquor column, where trace amounts of triethylamine in the alkali mother liquor are extracted from the top of the column.

[0003] The triethylamine recovered by the above-mentioned existing methods is of high purity and low impurity content, making it suitable for reuse in glyphosate production. Technically, moisture content is generally the primary concern. However, as the number of triethylamine regeneration and recycling cycles increases, the triethylamine recovered by the existing methods is enriched with impurity amines (miscellaneous amines), such as monoethylamine, diethylamine, and methylamine, compared to freshly replenished triethylamine. In severe cases, this can lead to substandard triethylamine quality and affect the energy efficiency and conversion rate of the entire glyphosate production system.

[0004] Furthermore, the existing ethylamine recovery process is a batch process. The crude triethylamine from the upper layer of the large stratified tank enters a dehydration kettle, where it is manually dehydrated by adding alkali flakes. The sodium hydroxide aqueous solution at the bottom must then be manually recovered and used for glyphosate crystallization and neutralization. The triethylamine in the upper layer of the dehydration kettle is then recycled as a catalyst for the glyphosate synthesis process. This process is complex, involves multiple equipment, is inefficient, labor-intensive, produces large amounts of tail gas, poses high safety and environmental risks, and has significant adverse environmental impacts. Furthermore, during the distillation process, the alkali mother liquor from the lower layer of the large stratified tank produces a large amount of aqueous solution at the top of the tower, which has a low triethylamine content, consumes a lot of steam energy, and is difficult to separate and recover.

[0005] Therefore, it is necessary to provide a continuous, efficient, safe and environmentally friendly triethylamine recovery method. Summary of the Invention

[0006] The present invention provides a method for continuously recovering and refining triethylamine in glyphosate production. The method feeds the liquid from the upper layer of a large stratified tank into a triethylamine refining tower, and the alkaline mother liquor from the lower layer of the large stratified tank into a triethylamine mother liquor rectification tower. This optimizes the distillation process operating parameters, improves the quality of the triethylamine product, and achieves continuous and efficient recovery of triethylamine. The method provided by the present invention reduces operating costs and enhances safety and environmental performance.

[0007] The basic concept of the technical solution adopted in the present invention is as follows:

[0008] A method for continuously recovering and refining triethylamine in glyphosate production comprises the following steps:

[0009] Step S1: adding alkali to neutralize the glyphosate mother liquor, and sending the crude triethylamine solution obtained by the reaction and layer displacement into a large layer separation tank for layer separation;

[0010] Step S2: the upper layer liquid obtained by layering is continuously overflowed into the triethylamine refining preheater for heating and then enters the triethylamine refining tower, and the lower layer alkali mother liquor is continuously transported to the triethylamine mother liquor distillation tower after being heated in the triethylamine mother liquor preheater; the top gas phases of the triethylamine refining tower and the triethylamine mother liquor distillation tower are condensed and simultaneously enter the reflux tank and then return to the top of each tower; wherein, the tower bottom discharge of the triethylamine refining tower is used as a heat source for the triethylamine refining preheater to preheat the upper layer liquid, and the tower bottom discharge of the triethylamine mother liquor distillation tower is used as a heat source for the triethylamine mother liquor preheater to preheat the lower layer alkali mother liquor;

[0011] Step S3: the upper liquid phase of the reflux tank is refluxed to the top of the triethylamine refining tower, and the lower liquid phase is refluxed to the top of the triethylamine mother liquor distillation tower, thereby realizing material coupling and negative feedback regulation of the double-tower distillation.

[0012] As one method, the top gas phase of the triethylamine refining tower is condensed by the top condenser of the refining tower and sent to a reflux tank, and then discharged from the upper part of the reflux tank and returned to the top of the triethylamine refining tower by a pump; the top gas phase of the triethylamine mother liquor distillation tower is condensed by the top condenser of the distillation tower and sent to a reflux tank, and then discharged from the lower part of the reflux tank and returned to the top of the triethylamine mother liquor distillation tower by a pump.

[0013] As one method, the operating pressure of the triethylamine refining tower is 0.1-0.15 MPa, the tower top temperature is 70-75° C., the tower bottom temperature is 92-102° C., and the reflux ratio is total reflux.

[0014] As one method, the operating pressure of the triethylamine mother liquor distillation tower is 0.1-0.15 MPa, the tower top temperature is 75-85° C., the tower bottom temperature is 100-105° C., and the reflux ratio is 0.15-0.45.

[0015] As one method, the stratification temperature of the stratification tank is 60-65° C., the triethylamine content in the upper layer liquid is ≥98%, and the triethylamine residual content in the lower layer alkali mother liquor is ≤0.5%.

[0016] As one embodiment, the residence time of the reflux tank is 15 to 20 minutes, the triethylamine content in the upper liquid phase is ≥98%, and the triethylamine content in the lower liquid phase is ≤1.5%.

[0017] As a method, the heat source of the reboiler of the refining tower kettle of the triethylamine refining tower is 0.5Mpa raw steam, and the refrigerant of the condenser at the top of the refining tower of the triethylamine refining tower is circulating water; the heat source of the triethylamine mother liquor reboiler of the triethylamine mother liquor distillation tower is 0.5Mpa raw steam, and the refrigerant of the condenser at the top of the distillation tower is circulating water;

[0018] Preferably, the stratification time in the stratification tank is 15-20 minutes, and the pH is 10-12.

[0019] The present invention also provides a system for continuously recovering and refining triethylamine in glyphosate production, which comprises a large layering tank, a triethylamine refining preheater, a triethylamine refining tower, a refining tower top condenser, a refining tower kettle reboiler, a reflux tank, a refining tower reflux pump, a triethylamine mother liquor preheater, a triethylamine mother liquor rectification tower, a rectification tower top condenser, a triethylamine mother liquor reflux pump and a triethylamine mother liquor reboiler;

[0020] The first outlet of the layered tank is connected to the middle of the triethylamine refining tower through the triethylamine refining preheater, the bottom outlet of the triethylamine refining tower is connected to the triethylamine refining preheater, the top outlet of the triethylamine refining tower is connected to the reflux tank through the refining tower top condenser, and the bottom of the triethylamine refining tower is connected to the reboiler of the refining tower;

[0021] The first outlet of the reflux tank is connected to the upper part of the triethylamine mother liquor distillation tower through a triethylamine mother liquor reflux pump, and the second outlet is connected to the upper part of the triethylamine refining tower through a refining tower reflux pump;

[0022] The second outlet of the stratification tank is connected to the middle of the triethylamine mother liquor distillation tower through the triethylamine mother liquor preheater, the top outlet of the triethylamine mother liquor distillation tower is connected to the reflux tank through the distillation tower top condenser, the bottom outlet of the triethylamine mother liquor distillation tower is connected to the triethylamine mother liquor preheater, and the bottom of the triethylamine mother liquor distillation tower is connected to the triethylamine mother liquor reboiler.

[0023] As a method, a porous distributor is provided radially below the feed port inside the large layered tank, and a plurality of corrugated inclined plates are provided between the bottom of the porous distributor and the bottom of the shell.

[0024] Preferably, the angle between the corrugated inclined plate and the horizontal direction is 55°; the layering time is 15-20 minutes, and the pH is 10-12.

[0025] As a way, the tower body material of the triethylamine refining tower and the mother liquor rectification tower is 2205 duplex stainless steel or titanium material, and the filler is a Pall ring or a regular filler.

[0026] Compared with the prior art, the present application has the following advantages:

[0027] 1. The present application provides a method for continuously recovering refined triethylamine in glyphosate production, which reduces labor intensity, enhances safety and environmental protection, and improves the purity of triethylamine to 99.99% compared with the prior art intermittent method.

[0028] 2. In the method of the present application, after continuous stratification in the stratified large tank, the upper liquid is sent to the triethylamine refining tower, and the lower mother liquor is sent to the triethylamine mother liquor rectification tower. The material temperature is 60-65℃, and after reducing the triethylamine dehydrating process, almost no heat is lost.

[0029] 3. In the method of the present application, the triethylamine refining tower outlet temperature is 92-102℃, which is used as a triethylamine refining preheater heat source; the triethylamine mother liquor rectification tower outlet temperature is 100-105℃, which is used as a triethylamine mother liquor rectification tower preheater, and the heat is fully utilized. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 is a schematic diagram of the system for continuously recovering refined triethylamine in glyphosate production according to the present application.

[0031] Figure 2 is a structural schematic diagram of the stratified large tank;

[0032] Figure 3 is Figure 2 is a structural schematic diagram of the multi-hole distributor in

[0033] Markings in the figure:

[0034] 1 stratified large tank, 1-1 feed inlet, 1-2 upper outlet, 1-3 multi-hole distributor, 1-4 corrugated inclined plate, 1-5 lower outlet, 2 triethylamine refining preheater, 3 triethylamine refining tower, 4 refining tower overhead condenser, 5 refining tower reboiler, 6 reflux tank, 7 refining tank reflux pump, 8 triethylamine mother liquor preheater, 9 triethylamine mother liquor rectification tower, 10 rectification tower overhead condenser, 11 triethylamine mother liquor reflux pump, 12 triethylamine mother liquor reboiler. DETAILED DESCRIPTION

[0035] The technical solutions of the embodiments of the present application are described below in a clear and complete manner. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the described embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the present application.

[0036] The technical concept of the present invention is specifically operated in the following continuous recovery and refining triethylamine system:

[0037] like Figure 1 As shown, the system includes a large layered tank 1, a triethylamine refining preheater 2, a triethylamine refining tower 3, a refining tower top condenser 4, a refining tower kettle reboiler 5, a reflux tank 6, a refining tower reflux pump 7, a triethylamine mother liquor preheater 8, a triethylamine mother liquor distillation tower 9, a distillation tower top condenser 10, a triethylamine mother liquor reflux pump 11 and a triethylamine mother liquor reboiler 12.

[0038] The first outlet of the layered tank 1 is connected to the middle of the triethylamine refining tower 3 through the triethylamine refining preheater 2, the bottom outlet of the triethylamine refining tower 3 is connected to the triethylamine product storage tank through the triethylamine refining preheater 2, and the top outlet of the triethylamine refining tower 3 is connected to the reflux tank 6 through the refining tower top condenser 4. The bottom of the triethylamine refining tower 3 is connected to the refining tower kettle reboiler 5.

[0039] The first outlet of the reflux tank 6 is connected to the upper part of the triethylamine mother liquor distillation tower 9 through the triethylamine mother liquor reflux pump 11, and the second outlet is connected to the upper part of the triethylamine refining tower 3 through the refining tower reflux pump 7.

[0040] The second outlet of the stratification tank 1 is connected to the middle of the triethylamine mother liquor distillation tower 9 via the triethylamine mother liquor preheater 8. The top outlet of the triethylamine mother liquor distillation tower 9 is connected to the reflux tank 6 via the distillation tower top condenser 10. The bottom outlet of the triethylamine mother liquor distillation tower 9 is connected to the alkaline solution storage device after passing through the triethylamine mother liquor preheater 8. The bottom of the triethylamine mother liquor distillation tower 9 is connected to a triethylamine mother liquor reboiler 12.

[0041] like Figure 2 The figure shows a schematic diagram of the structure of a layered large tank 1. The layered large tank 1 includes a horizontal shell, in which a porous distributor 1-3 is provided radially, and a plurality of corrugated inclined plates 1-4 (with an angle of 55° to the horizontal direction) are provided below the porous distributor 1-3 and between the bottom of the horizontal shell. A feed port 1-1 and an upper discharge port 1-2 are provided above the horizontal shell, and a lower discharge port 1-5 is provided at the bottom of the horizontal shell. Figure 3 As shown, the porous distributors 1-3 are plate-like structures with small holes of various sizes, which are conducive to the pre-separation of light and heavy components.

[0042] The following is a detailed introduction to the workflow of the above system:

[0043] The upper layer liquid of the layered tank 1 is mainly triethylamine and a small amount of water, and the temperature is 60-65℃, which is sent to the triethylamine refining preheater 2 to be heated to 70-75℃, and then is sent to the triethylamine refining tower 3 for rectification. The triethylamine refining tower 3 obtains triethylamine product with a purity of 99.99wt% at the bottom, and enters the triethylamine refining preheater 2 as a heat source to heat the raw material. The top of the triethylamine refining tower 3 is a mixture of triethylamine and water, which is condensed after passing through the top condenser 4 of the refining tower, and then is sent to the reflux tank 6, and is discharged from the second outlet of the upper part of the reflux tank 6 and is pumped back to the top or upper part of the triethylamine refining tower 3 by the reflux pump 7 of the refining tower.

[0044] The liquid in the lower layer of the layered tank 1 is mainly base mother liquor and a small amount of triethylamine, which is heated to 75-85℃ by the triethylamine mother liquor preheater 8, and then is sent to the triethylamine mother liquor rectification tower 9. The discharge at the bottom outlet of the triethylamine mother liquor rectification tower 9 is a base solution, and enters the triethylamine mother liquor preheater 8 as a heat source. The top output of the triethylamine mother liquor rectification tower 9 is triethylamine and a small amount of water, which is condensed after entering the top condenser 10 of the rectification tower, and then is sent to the reflux tank 6, and is pumped back to the upper part of the triethylamine refining tower 3 by the reflux pump 7 of the refining tower.

[0045] Based on the description of the system structure and the working process, it can be seen that the method of the present application adopts the innovative rectification system integration design process of “layered tank 1 upper and lower layer branch processing + double tower (triethylamine refining tower 3 and triethylamine mother liquor rectification tower 9) cooperative rectification + double tower shared reflux tank 6”, which realizes a significant technical breakthrough through multi-stage separation and cooperative optimization.

[0046] Firstly, the layered tank 1 adopts the density gradient phase separation technology, and the light and heavy components are pre-separated through the multi-hole distributor 1-3 (the separation efficiency is improved by 15%-20%), the upper layer light component overflows into the triethylamine refining tower 3, and the lower layer heavy component is sent to the triethylamine mother liquor rectification tower 9, which effectively reduces the back mixing phenomenon (the back mixing amount is reduced by 30%). The material temperature is 60-65℃, and after the dehydration process of putting in pieces of caustic soda, almost no heat is lost, which reduces the energy consumption of the system. The operating temperature of the layered tank 1 is 60-65℃, which significantly reduces the liquid phase flow resistance and accelerates the gravity sedimentation. Moreover, a multi-hole distributor 1-3 is arranged below the feed inlet in the layered tank 1 to realize the pre-separation of light and heavy components, and a plurality of groups of corrugated inclined plates 1-4 (with an inclination angle of 55° to the horizontal direction) are additionally arranged, so that the effective sedimentation area is increased by 3 times, and the stratification time is shortened to 15-20 minutes. The pH is controlled between 10 and 12, which further accelerates the water droplet coalescence rate.

[0047] Secondly, the common reflux tank 6 realizes the fluid mechanics coupling of the double-tower rectification section, compared with the traditional double-tower configuration, the tank volume is reduced by 40% (the typical design volume coefficient is reduced from 1.8 to 1.2), the reflux tank 6 forms a buffer capacity pool (the residence time is extended to 15-20 minutes), and the response time to the feed fluctuation (±10% flow change) is extended by 3 times.

[0048] Thirdly, the material coupling between the double towers forms a negative feedback mechanism, when the triethylamine refining tower 3 is subjected to load fluctuation, the triethylamine mother liquor rectification tower 9 can automatically adjust the operating parameters, and the operating stability and process adaptability are improved.

[0049] Embodiment 1

[0050] Step S1, after the acid mother liquor in the glyphosate production process is neutralized by adding alkali, the crude triethylamine solution replaced by reaction layering is sent to the layering large tank 1 at a flow rate of 32000 kg / h, the triethylamine content is 1wt%, the operating temperature is 65℃, the operating pressure is normal pressure, and the pH of the triethylamine solution is 11.

[0051] Step S2, the temperature of the upper liquid of the layering large tank 1 is 65℃, which is overflowed at normal pressure and sent to the triethylamine refining preheater 2 to be heated to 74℃, and then enters the triethylamine refining tower 3, and the flow rate is controlled by the automatic adjusting valve group to be 2757 kg / h. The triethylamine refining preheater 2 takes the tower bottom product of the triethylamine refining tower 3 as the heat source, the temperature of the tower bottom product is reduced from 94℃ to 79℃, the tower bottom product stream is used as the heat source, and the preheater load is 25463 Kal / h.

[0052] The top operating pressure of triethylamine refining tower 3 is 102 kPa(A), the bottom operating pressure is 117 kPa(A), the top operating temperature is 74°C, the bottom operating temperature is 93°C, and total reflux is applied. All triethylamine extracted from the top of triethylamine mother liquor distillation tower 9 is fed to triethylamine refining tower 3. Triethylamine refining tower 3 is made of titanium and packed with random packing Pall rings. The top gas phase is a mixture of triethylamine and water at a flow rate of 702 kg / h. After condensation in refining tower overhead condenser 4 at a temperature of 72°C, it is fed to reflux drum 6, from which the gas is discharged and pumped back to the top of triethylamine refining tower 3 at a reflux rate of 1144.5 kg / h. The mass fraction of tower still product triethylamine is 99.99wt%, and flow is 3199.5kg / h. The tower still output and tower still liquid level are automatically controlled, and the controlled liquid level is 50%, and the triethylamine recovery rate is 99.98%. Refining tower still reboiler 5 is heated by raw steam with 0.5Mpa (A), and the steam consumption is 268kg / h, and it is 135277Kal / h that steam provides heat load. Raw steam is interlocked with tower still temperature, and the automatic control tower still temperature is at 93~94 ℃, total reflux, and the triethylamine that the overhead distillation of a part of triethylamine mother liquor rectifying tower 9 comes out is sent into triethylamine treating tower 3, and the tower top temperature of control triethylamine treating tower 3 is 74~75 ℃.

[0053] The lower layer of the stratification tank 1 consists primarily of alkali mother liquor and a small amount of triethylamine. The liquid is controlled by an automatic regulating valve assembly at a flow rate of 29,243 kg / h and a temperature of 60°C. After being heated to 80°C in a triethylamine mother liquor preheater 8, it is fed into a triethylamine mother liquor distillation column 9. The triethylamine mother liquor preheater 8 uses the bottom stream of the triethylamine mother liquor distillation column 9 as a heat source, cooling the bottom stream from 103°C to 80°C. The bottom stream acts as a heat source, providing a preheater load of 690,604 kal / h. The top operating pressure of the triethylamine mother liquor distillation column 9 is 102 kPa(A), the bottom operating pressure is 112 kPa(A), the top operating temperature is 80°C, the bottom operating temperature is 103°C, and the reflux ratio is 0.3. The triethylamine mother liquor distillation column 9 is made of titanium and packed with random packing Pall rings. The bottom discharge of the triethylamine mother liquor distillation tower 9 is an alkaline aqueous solution. The bottom discharge is automatically controlled with the bottom liquid level, maintaining the liquid level at 50% at a flow rate of 28,800 kg / h, which serves as the heat source for the triethylamine mother liquor preheater 8. The overhead vapor phase of the triethylamine mother liquor distillation tower 9 consists of 86.8 wt% triethylamine and 13.2 wt% water at a flow rate of 576 kg / h. After condensation in the top condenser 10, it is fed to the reflux drum 6, where the condensed temperature reaches 72°C. The bottom discharge of the reflux drum 6 is then pumped back to the top of the triethylamine mother liquor distillation tower 9 at a reflux rate of 133 kg / h. The refrigerant for the top condenser 10 is recycled water. The live steam is linked to the bottom temperature, automatically controlling the bottom temperature at 103-104°C. The reflux rate is linked to the top temperature, maintaining the top temperature of the triethylamine refining tower 3 at 80-81°C.

[0054] The triethylamine mother liquor reboiler 12 is heated by 0.5 MPa (A) live steam, the steam consumption is 1457 kg / h, and the steam provides a heat load of 733493 Kal / h.

[0055] Step S3: The triethylamine content in the upper liquid phase of the reflux tank 6 is 98.24 wt%, and the upper liquid phase is pumped back to the triethylamine refining column 3 by the refining column reflux pump 7. The triethylamine content in the lower liquid phase of the reflux tank 6 is 1.3 wt%, and the lower liquid phase is pumped back to the top of the triethylamine mother liquor rectification column 9 by the triethylamine mother liquor reflux pump 11. The material temperature in the reflux tank 6 is 68°C at normal pressure.

[0056] When the feed flow fluctuates ±15%, the steam and the double-column column temperature are automatically adjusted, and the flow of the lower liquid phase of the reflux tank (6) refluxed to the triethylamine mother liquor column 9 is automatically adjusted, so that the double-column pressure difference is maintained within ±5 kPa.

[0057] The final column product triethylamine mass fraction is 99.99 wt%, and the triethylamine recovery rate is 99.98%. Since the column material provides heat for the preheater, the energy utilization rate is improved.

[0058] In the traditional process, the crude triethylamine in the upper layer of the layered tank 1 is not purified by rectification, but is directly recycled back to the plant for use. The crude triethylamine in the lower layer of the layered tank 1 is sent to the triethylamine mother liquor column for single-column rectification. The column material is discharged after being condensed by circulating water, and 690604 Kal / h of heat is directly wasted, causing energy waste and environmental pollution.

[0059] Example 2

[0060] Step S1: After the acid mother liquor in the glyphosate production process is neutralized by adding alkali, the ethylamine solution displaced by reaction and layering is sent to the layered tank 1 at a flow rate of 16000 kg / h, the triethylamine content is 1 wt%, the operating temperature is 64°C, the operating pressure is normal pressure, and the pH of the triethylamine solution is 11.

[0061] Step S2: The temperature of the upper liquid of the layered tank 1 is 64°C, which is overflowed at normal pressure into the triethylamine refining preheater 2 and heated to 72°C, and then enters the triethylamine refining column 3, and the flow is controlled by the automatic control valve group to be 1380 kg / h. The triethylamine refining preheater 2 uses the column product of the triethylamine refining column 3 as a heat source, and the temperature of the column product is reduced from 92°C to 77°C. The column product stream is used as a heat source, and the preheater load is 12750 Kal / h.

[0062] The overhead operating pressure of the triethylamine refining column 3 is 101 KPa(A), the column bottom operating pressure is 113 KPa(A), the overhead operating temperature is 73°C, the column bottom operating temperature is 92°C, total reflux is used, and all of the triethylamine taken from the top of the triethylamine mother liquor rectifying column 9 is fed into the triethylamine refining column 3. The material of the triethylamine refining column 3 is titanium, and the packing is the scattered packing of Pahl ring. The overhead gas phase of the triethylamine refining column 3 is a mixture of triethylamine and water, the flow rate is 355 kg / h, the temperature is 72°C after condensation by the overhead condenser 4 of the refining column, and the condensate is fed into the reflux tank 6, and then discharged from the upper part of the reflux tank 6 and pumped back to the top of the triethylamine refining column 3, the reflux flow rate is 1025 kg / h. The mass fraction of the column bottom product triethylamine is 99.99 wt%, the flow rate is 1600 kg / h, the column bottom discharge and the column liquid level are automatically controlled, the control liquid level is 50%, and the triethylamine recovery rate is 99.99%. The column bottom reboiler 5 of the refining column is heated by 0.5 MPa(A) live steam, the steam consumption is 140 kg / h. The live steam is linked with the column bottom temperature, the column bottom temperature is automatically controlled at 92-93°C, the reflux flow rate is linked with the overhead temperature, and the overhead temperature of the triethylamine refining column 3 is controlled at 72-73°C.

[0063] The lower layer liquid of the layered large tank 1 is mostly alkali mother liquor and a small amount of triethylamine, the flow rate is 14620 g / h, and the temperature is 61°C, which is heated and raised to 82°C by the triethylamine mother liquor preheater 8 and then fed into the triethylamine mother liquor rectifying column 9. The triethylamine mother liquor preheater 8 uses the column bottom stream of the triethylamine mother liquor rectifying column 9 as the heat source, and the column bottom material temperature is lowered from 104°C to 81°C. The column bottom stream is used as the heat source, and the preheater load is 345300 Kal / h. The overhead operating pressure of the triethylamine mother liquor rectifying column 9 is 103 KPa(A), the column bottom operating pressure is 108 KPa(A), the overhead operating temperature is 80°C, the column bottom operating temperature is 102°C, and the reflux ratio is 0.35. The material of the triethylamine mother liquor rectifying column 9 is titanium, and the packing is the scattered packing of Pahl ring. The column bottom discharge of the triethylamine mother liquor rectifying column 9 is an aqueous alkali solution, the column bottom discharge and the column liquid level are automatically controlled, the control liquid level is 50%, the flow rate is 14400 kg / h, and the column bottom discharge is used as the heat source of the triethylamine mother liquor preheater 8. The overhead gas phase of the triethylamine mother liquor rectifying column 9 is 86.8 wt% triethylamine and 13.2 wt% water, the flow rate is 220 kg / h, which is condensed by the rectifying column overhead condenser 10 and then fed into the reflux tank 6, and the condensed temperature is 71°C. The condensate is discharged from the lower part of the reflux tank 6 and pumped back to the top of the triethylamine mother liquor rectifying column 9, and the reflux flow rate is 68 kg / h. The coolant of the rectifying column overhead condenser 10 is circulating water. The live steam is linked with the column bottom temperature, the column bottom temperature is automatically controlled at 101-102°C, the reflux flow rate is linked with the overhead temperature, and the overhead temperature of the triethylamine refining column 3 is controlled at 80-81°C.

[0064] The triethylamine mother liquor reboiler 12 is heated by 0.5 MPa(A) live steam, and the steam consumption is 760 kg / h.

[0065] Step S3: The content of triethylamine in the upper liquid phase of the reflux tank 6 is 98.3wt%, the upper liquid is pumped back to the triethylamine refining tower 3, and the content of triethylamine in the lower liquid phase of the reflux tank 6 is 1.29%, the lower liquid phase is pumped back to the top of the triethylamine mother liquor rectification tower 9. The temperature of the material in the reflux tank 6 is 68℃ under normal pressure.

[0066] The mass fraction of the final tower kettle product triethylamine is 99.99%, and the triethylamine recovery rate is 99.99%.

[0067] Comparative Example 1

[0068] Using the existing intermittent process, the crude triethylamine in the upper layer of the layered large tank 1 enters the dehydration kettle, and is dehydrated by manually adding sodium hydroxide tablets, and then the bottom sodium hydroxide aqueous solution is manually recovered for use in the glyphosate crystallization neutralization; the triethylamine in the upper part of the dehydration kettle is used as a catalyst and recycled to the glyphosate synthesis process.

[0069] This process is complex in operation, involves many devices, has low efficiency, high labor intensity, large tail gas, high safety and environmental protection risks, and has a large adverse impact on the environment. In addition, the alkali mother liquor in the lower layer of the layered large tank 1 will produce a large amount of aqueous solution at the top of the rectification process, with low triethylamine content and high steam energy consumption, and the aqueous solution is difficult to separate and recover.

[0070] The present application is a continuous operation, the whole process is continuous and automatic, greatly reducing the frequency of worker operation, greatly reducing the safety and environmental protection risks, and the product quality is higher. The steam consumption of the present application is reduced by about 15% compared with the original process.

[0071] Comparative Example 2

[0072] The difference from Example 1 is that the triethylamine refining tower 3 and the triethylamine mother liquor rectification tower 9 are independently provided with a reflux device respectively.

[0073] This scheme needs to set up 2 reflux tanks, compared with sharing 1 reflux tank, the tank volume increases by 40%, increasing the equipment investment.

[0074] The system process of the present application uses a reflux tank 6 with a specific structure, which has the function of gravity stratification, reducing the material turnover time. When the feed flow and content fluctuate, the reflux tank 6 forms a buffer capacity pool, the response time to feed fluctuation (±10% flow change) is prolonged by 3 times, and the triethylamine recovery rate is increased from 99.65% to 99.98%.

Claims

1. A method for continuously recovering and refining triethylamine in glyphosate production, characterized in that: The following steps are involved: Step S1: adding alkali to neutralize the glyphosate mother liquor, and sending the crude triethylamine solution obtained by the reaction and layer displacement into the large layer separation tank (1) for layer separation; Step S2: the upper layer liquid obtained by layering is continuously overflowed into the triethylamine refining preheater (2) for heating and then enters the triethylamine refining tower (3); the lower layer alkali mother liquor is heated in the triethylamine mother liquor preheater (8) and then continuously transported to the triethylamine mother liquor distillation tower (9); the top gas phases of the triethylamine refining tower (3) and the triethylamine mother liquor distillation tower (9) are condensed and simultaneously enter the reflux tank (6) and then return to the top of each tower; wherein the bottom discharge of the triethylamine refining tower (3) is used as a heat source for the triethylamine refining preheater (2) to preheat the upper layer liquid, and the bottom discharge of the triethylamine mother liquor distillation tower (9) is used as a heat source for the triethylamine mother liquor preheater (8) to preheat the lower layer alkali mother liquor; Step S3: The upper liquid phase of the reflux tank (6) is refluxed to the top of the triethylamine refining tower (3), and the lower liquid phase is refluxed to the top of the triethylamine mother liquor distillation tower (9), thereby realizing material coupling and negative feedback regulation of the double-tower distillation.

2. The method for continuously recovering and refining triethylamine in glyphosate production according to claim 1, wherein: The top gas phase of the triethylamine refining tower (3) is condensed by the refining tower top condenser (4) and then sent to the reflux tank (6), and is discharged from the upper part of the reflux tank (6) and returned to the top of the triethylamine refining tower (3) through a pump; the top gas phase of the triethylamine mother liquor distillation tower (9) is condensed by the distillation tower top condenser (10) and then sent to the reflux tank (6), and then is discharged from the lower part of the reflux tank (6) and returned to the top of the triethylamine mother liquor distillation tower (9) through a pump.

3. The method for continuously recovering and refining triethylamine in glyphosate production according to claim 1, characterized in that: The operating pressure of the triethylamine refining tower (3) is 0.1-0.15 MPa, the tower top temperature is 70-75°C, the tower bottom temperature is 92-102°C, and the reflux ratio is full reflux.

4. The method for continuously recovering and refining triethylamine in glyphosate production according to claim 1, characterized in that: The operating pressure of the triethylamine mother liquor distillation tower (9) is 0.1-0.15 MPa, the tower top temperature is 75-85° C., the tower bottom temperature is 100-105° C., and the reflux ratio is 0.15-0.

45.

5. The method for continuously recovering and refining triethylamine in glyphosate production according to claim 1, characterized in that: The layering temperature of the large layering tank (1) is 60-65° C., the content of triethylamine in the upper layer liquid is ≥98%, and the residual amount of triethylamine in the lower layer alkali mother liquor is ≤0.5%.

6. The method for continuously recovering and refining triethylamine in glyphosate production according to claim 1, characterized in that: The residence time of the reflux tank (6) is 15 to 20 minutes, the triethylamine content in the upper liquid phase is ≥98%, and the triethylamine content in the lower liquid phase is ≤1.5%.

7. The method for continuously recovering and refining triethylamine in glyphosate production according to claim 1, characterized in that: The heat source of the reboiler (5) of the refining tower kettle of the triethylamine refining tower (3) is 0.5Mpa raw steam, and the refrigerant of the refining tower top condenser (4) of the triethylamine refining tower (3) is circulating water; the heat source of the triethylamine mother liquor reboiler (12) of the triethylamine mother liquor rectifying tower (9) is 0.5Mpa raw steam, and the refrigerant of the rectifying tower top condenser (10) is circulating water; Preferably, the stratification time in the stratification tank (1) is 15-20 minutes, and the pH is 10-12.

8. A system for continuously recovering and refining triethylamine in glyphosate production, characterized in that: The invention comprises a large layering tank (1), a triethylamine refining preheater (2), a triethylamine refining tower (3), a refining tower top condenser (4), a refining tower kettle reboiler (5), a reflux tank (6), a refining tower reflux pump (7), a triethylamine mother liquor preheater (8), a triethylamine mother liquor rectifying tower (9), a rectifying tower top condenser (10), a triethylamine mother liquor reflux pump (11) and a triethylamine mother liquor reboiler (12); The first outlet of the large layered tank (1) is connected to the middle of the triethylamine refining tower (3) through the triethylamine refining preheater (2), the bottom outlet of the triethylamine refining tower (3) is connected to the triethylamine refining preheater (2), the top outlet of the triethylamine refining tower (3) is connected to the reflux tank (6) through the refining tower top condenser (4), and the bottom of the triethylamine refining tower (3) is connected to the refining tower kettle reboiler (5); The first outlet of the reflux tank (6) is connected to the upper part of the triethylamine mother liquor distillation tower (9) through the triethylamine mother liquor reflux pump (11), and the second outlet is connected to the upper part of the triethylamine refining tower (3) through the refining tower reflux pump (7); The second outlet of the large layering tank (1) is connected to the middle of the triethylamine mother liquor distillation tower (9) via the triethylamine mother liquor preheater (8); the top outlet of the triethylamine mother liquor distillation tower (9) is connected to the reflux tank (6) via the distillation tower top condenser (10); the bottom outlet of the triethylamine mother liquor distillation tower (9) is connected to the triethylamine mother liquor preheater (8); and the bottom of the triethylamine mother liquor distillation tower (9) is connected to the triethylamine mother liquor reboiler (12).

9. The system for continuously recovering and refining triethylamine in glyphosate production according to claim 8, characterized in that: A porous distributor (1-3) is provided radially below the feed port (1-1) inside the large layered tank (1), and a plurality of corrugated inclined plates (1-4) are provided between the bottom of the porous distributor (1-3) and the bottom of the shell. Preferably, the angle between the corrugated inclined plate and the horizontal direction is 55°; the layering time is 15-20 minutes, and the pH is 10-12.

10. The system for continuously recovering and refining triethylamine in glyphosate production according to claim 8, characterized in that: The tower bodies of the triethylamine refining tower (3) and the mother liquor distillation tower (9) are made of 2205 duplex stainless steel or titanium, and the fillers are ball rings or structured packings.

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