CN109678704B - Method for automatically controlling mono-esterification reaction of adipic acid - Google Patents
Method for automatically controlling mono-esterification reaction of adipic acid Download PDFInfo
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- CN109678704B CN109678704B CN201811503627.3A CN201811503627A CN109678704B CN 109678704 B CN109678704 B CN 109678704B CN 201811503627 A CN201811503627 A CN 201811503627A CN 109678704 B CN109678704 B CN 109678704B
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Abstract
The invention relates to a method for automatically controlling the mono-esterification reaction of adipic acid, which mainly solves the problems of poor accuracy, poor reliability, poor anti-interference capability and low production efficiency in the prior art. The invention adopts a method for automatically controlling adipic acid mono-esterification reaction, wherein an adipic acid raw material enters a pre-esterification reaction kettle after passing through a weighing hopper, an intermediate hopper and a spiral conveyor, and contacts with a methanol raw material, a mixture after reaction enters a pre-esterification buffer tank, and a material flow at the bottom of the pre-esterification buffer tank is sent to a catalytic reaction tower as an adipic acid mono-esterification product; wherein, the pipeline that the intermediate hopper links with the auger conveyor is equipped with the rotary valve, and the rotary valve is the proportional signal control, and establish the correlation with methyl alcohol feed flow metering valve, the technical scheme of the raw materials proportion of control entering the pre-esterification reaction kettle has solved above-mentioned problem betterly, can be used in adipic acid mono-esterification production.
Description
Technical Field
The invention relates to a method for automatically controlling the mono-esterification reaction of adipic acid, belonging to the technical field of fire safety.
Background
Monomethyl adipate, also known as fatty acid methyl ester, having a molecular weight of 160 and a molecular formula C7H12O4The pure product is colorless, clear and transparent liquid, is easy to dissolve in alcohol ether and insoluble in water, is an important organic synthetic raw material and is widely appliedIt can be used for synthesizing high-grade surfactant, high-grade lubricating oil and fuel additive, emulsifier product and perfume solvent, etc., and can be used as dye intermediate, and can be prepared from adipic acid and methanol according to a certain mole ratio under the acidic condition.
Adipic acid is commonly called as adipic acid, has the molecular weight of 146, is white crystal at normal temperature, has the melting point of 152 ℃ and the boiling point of 330 ℃, and is easy to sublimate when being heated. Adipic acid is the most important aliphatic dicarboxylic acid in industry and is an important organic chemical raw material. Adipic acid as an organic intermediate is mainly used for synthesizing polyurethane and plasticizer, and is widely applied to the fields of polyester foam plastics, adhesives, food additives, insecticides, high-grade lubricating oil, medicines and the like.
The methanol has the molecular weight of 32, the melting point of-97 ℃, the boiling point of 64.7 ℃, is liquid at normal temperature, is volatile, can be mutually dissolved with water in any proportion, and does not form a constant boiling mixture; methanol is extremely toxic and inflammable, is the third important basic chemical raw material second to olefins and aromatic hydrocarbons, and is mainly used for producing solvents and fuels.
At normal temperature, adipic acid and methanol are slightly soluble and mixed according to a certain acid-alcohol ratio to carry out a series of esterification reactions. In the esterification reaction, in order to improve the esterification reaction efficiency, the basic requirements of the esterification reactor are that the esterification reactor has good material mixing, effective temperature control and timely water removal capability. At present, a manual control method of mechanical stirring is mostly adopted in both a laboratory esterification reactor and an industrial large-scale reaction device. Compared with the traditional manual operation, the automatic control process control system has the advantages of high reliability, strong anti-interference capability, simple programming, convenient use, complete functions and the like, can effectively shorten the production time and improve the production efficiency, is an important technology for industrial process, and has extremely important significance.
Disclosure of Invention
The invention aims to solve the technical problems of poor accuracy, poor reliability, poor anti-interference capability and low production efficiency in the prior art, provides a novel method for automatically controlling the mono-esterification reaction of adipic acid, and has the advantages of high accuracy, good reliability, strong anti-interference capability and high production efficiency.
In order to solve the problems, the technical scheme adopted by the invention is as follows: a method for automatically controlling adipic acid mono-esterification reaction comprises the steps that adipic acid raw materials enter a pre-esterification reaction kettle after passing through a weighing hopper, an intermediate hopper and a spiral conveyor, the adipic acid raw materials are contacted with a methanol raw material, a mixture after reaction enters a pre-esterification buffer tank, and material flow at the bottom of the pre-esterification buffer tank is sent to a catalytic reaction tower as an adipic acid mono-esterification product; the pipeline connecting the middle hopper and the screw conveyer is provided with a rotary valve, the rotary valve is driven by a motor to enable an impeller with an equal-division structure to rotate in the shell, adipic acid in a feeding device at the upper part of the shell is filled in a cavity of the impeller and rotates to the lower part of the shell along with the impeller, and the adipic acid is uniformly and continuously discharged downstream according to the requirement of a conveying system. The rotary valve is controlled by a proportional signal, is associated with a methanol feed flow metering valve, and controls the proportion of raw materials entering the pre-esterification reaction kettle; the automatic control process of the adipic acid mono-esterification reaction comprises the following steps:
(1) starting;
(2) opening an emptying valve XV-1 above the weighing hopper, and detecting that the pressure PI-1 of the weighing hopper is an atmospheric pressure value by a pressure gauge 20 above the weighing hopper;
(3) closing the gate valve XV-3, weighing the adipic acid in a weighing hopper, and enabling the feeding amount of the adipic acid to reach a set value;
(4) opening an emptying valve XV-2 above the intermediate hopper, closing a gate valve XV-7, and detecting that the intermediate hopper PI-2 is at an atmospheric pressure value by a pressure gauge 21 above the intermediate hopper;
(5) the adipic acid enters an intermediate hopper;
(6) closing the gate valve XV-19, opening the regulating valve XV-11, and controlling the pressure in the intermediate hopper to reach a set value;
(7) closing the regulating valve XV-11, opening the nitrogen regulating valve XV-17, and filling nitrogen;
(8) when the pressure of the pre-esterification reaction kettle reaches a set value, closing a nitrogen regulating valve XV-17;
(9) opening a methanol feed valve XV-12, and closing the methanol feed valve XV-12 after the designed flow of methanol is reached;
(10) opening a gate valve XV-7, conveying materials by a screw conveyor, and feeding adipic acid through a rotary valve;
(11) stirring, reacting, sampling, discharging the materials in the pre-esterification reaction kettle to a pre-esterification buffer tank after the acid value reaches the standard.
In the technical scheme, preferably, a gate valve XV-3 is arranged at an outlet at the bottom of the weighing hopper; a gate valve XV-19 is arranged between the outlet at the bottom of the middle hopper and the rotary valve; the top parts of the weighing hopper and the middle hopper are provided with dust removing equipment; a pipeline for removing a torch is arranged at the top of the pre-esterification buffer tank; a gate valve XV-7 is arranged on a pipeline between the screw conveyor and the pre-esterification reaction kettle.
In the above technical solution, preferably, the nitrogen gas line is connected to the intermediate hopper and the pre-esterification reaction kettle.
In the above technical solution, preferably, the operating conditions of the pre-esterification reaction kettle satisfy: the wall temperature is not less than 130 ℃, the dissolving time is not less than 60min, and when the solution temperature exceeds 82 ℃, the adipic acid is completely dissolved; adipic acid in solution begins to precipitate when the temperature of the solution is less than 70 ℃.
In the above technical solution, preferably, the adipic acid and methanol mixed solution is heated to 85 ℃ or higher, and then continuously fed, and the temperature of the pipeline and the feeding pump in the whole feeding process is maintained at 85 ℃ or higher.
In the above technical solution, preferably, the operating conditions of the pre-esterification reaction kettle are as follows: the reaction temperature is 130-150 ℃, and the molar ratio of methanol to adipic acid is 3-4: 1, the reaction time is 2-4 h, and the reaction pressure is the saturated vapor pressure of the methanol at 130-150 ℃.
In the technical solution, preferably, F1(m)＝t*73*M(t)/(80*Y)，F1(m) is the feed of adipic acid (unit: t), t is the residence time of the reaction (unit: h), M (t) is the expected yield of monomethyl adipate per hour (unit: t), and Y is the yield of the monoesterification reaction.
In the above technical scheme, preferably, F (T) ^ 10^ 7.87863-1473.11/(T +230) ], F (T) is the pressure of the pre-esterification reaction kettle (unit: mmHg), and T is the feeding temperature of methanol (unit: DEG C).
In the above technical solution, preferably, F2(m)＝F1(m)*n*16/73，F2(m) is the feeding amount of methanol, (unit: t), n is the feeding molar ratio of adipic acid and methanol; the feeding amount of the adipic acid and the methanol adopts a ratio control method, a rotary valve is controlled by a ratio controller, and when the methanol is fed, the adipic acid is fed according to a preset molar feeding ratio.
In the above technical scheme, preferably, the pre-esterification reaction kettle adopts external heating, wherein jacketed heating can be replaced by coil tube heating.
During the esterification reaction, in order to achieve a certain esterification rate, the retention time of the materials in the reactor must be ensured. When the retention time of the materials in the esterification reactor is too long, the steam chamber of the esterification reactor becomes small, the materials are easily carried into the esterification separation tower, the esterification separation tower is blocked, and water generated by the esterification reaction cannot be discharged out of the system, so that the normal running of the esterification reaction is influenced; when the retention time is too short, the esterification rate cannot meet the corresponding requirement, and the product quality is influenced. According to the automatic control scheme, the residence time is automatically controlled, so that the problems can be effectively avoided, the mixing effect in the reactor is improved, the heat transfer and mass transfer of materials in the reactor are effectively improved, the reaction rate and the conversion rate are improved, the generation of byproducts is reduced, and a better technical effect is achieved.
Drawings
FIG. 1 is a schematic flow diagram of the process of the present invention.
In FIG. 1, 1 is an emptying valve XV-1, 2 is an emptying valve XV-2, 3 is a gate valve XV-3, 4 is a weighing hopper, 5 is an intermediate hopper, 6 is a screw conveyor, 7 is a gate valve XV-7, 8, 9 are dissolution reaction kettles, 10 is a pre-esterification buffer tank, 11 is an adjusting valve XV-11, 12 is a methanol feeding valve XV-12, 13 is a methanol feeding heater, 14 is adipic acid, 15 is methanol, 16 is nitrogen, 17 is an adjusting valve XV-17, 18 is a rotary valve, 19 is a gate valve XV-19, 20 is a pressure gauge PI-20, and 21 is a pressure gauge PI-21.
FIG. 2 is a programmed flow diagram of adipic acid monoesterification.
The present invention will be further illustrated by the following examples, but is not limited to these examples.
Detailed Description
[ example 1 ]
A method for automatically controlling adipic acid mono-esterification reaction is disclosed, as shown in figure 1, adipic acid raw material passes through a weighing hopper, an intermediate hopper and a spiral conveyor and then enters a pre-esterification reaction kettle to contact with methanol raw material, the mixture after reaction enters a pre-esterification buffer tank, and the bottom material flow of the pre-esterification buffer tank is sent to a catalytic reaction tower as adipic acid mono-esterification product; the pipeline connecting the middle hopper and the screw conveyer is provided with a rotary valve, the rotary valve is driven by a motor to enable an impeller with an equal-division structure to rotate in the shell, adipic acid in a feeding device at the upper part of the shell is filled in a cavity of the impeller and rotates to the lower part of the shell along with the impeller, and the adipic acid is uniformly and continuously discharged downstream according to the requirement of a conveying system. The rotary valve is controlled by a proportional signal, is associated with a methanol feed flow metering valve, and controls the proportion of raw materials entering the pre-esterification reaction kettle; the automated control process for the adipic acid monoesterification reaction (as shown in FIG. 2) comprises:
(1) starting;
(2) opening an emptying valve XV-1 above the weighing hopper, and detecting that the pressure PI-1 of the weighing hopper is an atmospheric pressure value by a pressure gauge 20 above the weighing hopper;
(3) closing the gate valve XV-3, weighing the adipic acid in a weighing hopper, and enabling the feeding amount of the adipic acid to reach a set value;
(4) opening an emptying valve XV-2 above the intermediate hopper, closing a gate valve XV-7, and detecting that the intermediate hopper PI-2 is at an atmospheric pressure value by a pressure gauge 21 above the intermediate hopper;
(5) the adipic acid enters an intermediate hopper;
(6) closing the gate valve XV-19, opening the regulating valve XV-11, and controlling the pressure in the intermediate hopper to reach a set value;
(7) closing the regulating valve XV-11, opening the nitrogen regulating valve XV-17, and filling nitrogen;
(8) when the pressure of the pre-esterification reaction kettle reaches a set value, closing a nitrogen regulating valve XV-17;
(9) opening a methanol feed valve XV-12, and closing the methanol feed valve XV-12 after the designed flow of methanol is reached;
(10) opening a gate valve XV-7, conveying materials by a screw conveyor, and feeding adipic acid through a rotary valve;
(11) stirring, reacting, sampling, discharging the materials in the pre-esterification reaction kettle to a pre-esterification buffer tank after the acid value reaches the standard.
A gate valve XV-3 is arranged at an outlet at the bottom of the weighing hopper; a gate valve XV-19 is arranged between the outlet at the bottom of the middle hopper and the rotary valve; the top parts of the weighing hopper and the middle hopper are provided with dust removing equipment; a pipeline for removing a torch is arranged at the top of the pre-esterification buffer tank; a gate valve XV-7 is arranged on a pipeline between the screw conveyor and the pre-esterification reaction kettle. The nitrogen pipeline is connected with the intermediate hopper and the pre-esterification reaction kettle. The operating conditions of the pre-esterification reaction kettle meet the following requirements: the wall temperature is not less than 130 ℃, the dissolving time is not less than 60min, and when the solution temperature exceeds 82 ℃, the adipic acid is completely dissolved; adipic acid in solution begins to precipitate when the temperature of the solution is less than 70 ℃. The adipic acid and methanol mixed solution is heated to more than 85 ℃ and then is continuously fed, and the temperature of a pipeline and a feeding pump in the whole feeding process is maintained to be more than 85 ℃.
The operating conditions of the pre-esterification reaction kettle are as follows: reaction temperature 130 ℃, methanol to adipic acid molar ratio 3: 1, the reaction time is 2 hours, and the reaction pressure is the saturated vapor pressure of the methanol at 130 ℃.
F1(m)＝t*73*M(t)/(80*Y)，F1(m) is the feed of adipic acid (unit: t), t is the residence time of the reaction (unit: h), M (t) is the expected yield of monomethyl adipate per hour (unit: t), and Y is the yield of the monoesterification reaction.
F (T) 10^ 7.87863-1473.11/(T +230) ], F (T) the pressure of the pre-esterification reaction kettle (unit: mmHg) and T the temperature of the methanol feed (unit:. degree. C).
F2(m)＝F1(m)*n*16/73，F2(m) is the feed amount of methanol (unit: t), and n is the feed molar ratio of adipic acid to methanol; the feeding amount of the adipic acid and the methanol adopts a ratio control method, a rotary valve is controlled by a ratio controller, and when the methanol is fed, the adipic acid is fed according to a preset molar feeding ratio.
In the above technical scheme, preferably, the pre-esterification reaction kettle adopts external heating, wherein jacketed heating can be replaced by coil tube heating.
In fig. 1, the adipic acid discharge system was operated intermittently and the weighing hopper was designed to be 1 day (24 hours). The solid feeding system is operated intermittently, and the intermediate hopper is designed for feeding materials according to the requirement of 2 hours. The pre-esterification unit adopts intermittent operation, and the pre-esterification reaction kettle is designed according to the reaction liquid amount for dissolving for 0.5 hour. The pre-esterification reaction kettle is heated by jacket steam, and the wall temperature is ensured to be above 130 ℃; circulating methanol from a methanol intermediate tank is pumped into the pre-esterification reaction kettle through a solvent methanol pump. Add circulating methanol (1800kg, required for 0.5 h); adding adipic acid solid (2737kg, required amount of 0.5 h) into a pre-esterification reaction kettle through a screw conveyor and a gate valve (double valve), and simultaneously starting a stirring paddle; closing the gate valve after the solid feeding is finished, introducing low-pressure steam into the jacket, heating, and stirring for about one hour until the low-pressure steam is dissolved; after sampling and inspection are qualified, opening a discharge valve, and putting the reaction liquid into a pre-esterification buffer tank; after material returning is finished, filling low-pressure nitrogen to ensure that the solution completely enters the buffer tank, closing the discharge valve, opening the emptying valve, and opening the gate valve to prepare the solution in the next kettle again after the pressure is reduced to normal pressure; and other pre-esterification reaction kettles are repeated according to the steps, so that the methanol solution of the adipic acid in the pre-esterification buffer tank meets the requirement of the subsequent production dosage.
When t is 2h, m (t) is 3t, and Y is 0.5, the feeding amount F of adipic acid1(m)＝10.95t。
When T is 130 ℃, the pressure F (T) is 6118.68mmHg in the pre-esterification reaction kettle
When F is present1(m) 10.95t, n 3, the amount of methanol fed F2(m)＝7.2t。
[ example 2 ]
A method for automatically controlling adipic acid mono-esterification reaction is disclosed, as shown in figure 1, adipic acid raw material passes through a weighing hopper, an intermediate hopper and a spiral conveyor and then enters a pre-esterification reaction kettle to contact with methanol raw material, the mixture after reaction enters a pre-esterification buffer tank, and the bottom material flow of the pre-esterification buffer tank is sent to a catalytic reaction tower as adipic acid mono-esterification product; the pipeline connecting the middle hopper and the screw conveyer is provided with a rotary valve, the rotary valve is driven by a motor to enable an impeller with an equal-division structure to rotate in the shell, adipic acid in a feeding device at the upper part of the shell is filled in a cavity of the impeller and rotates to the lower part of the shell along with the impeller, and the adipic acid is uniformly and continuously discharged downstream according to the requirement of a conveying system. The rotary valve is controlled by a proportional signal, is associated with a methanol feed flow metering valve, and controls the proportion of raw materials entering the pre-esterification reaction kettle; the automated control process for the adipic acid monoesterification reaction (as shown in FIG. 2) comprises:
(1) starting;
(2) opening an emptying valve XV-1 above the weighing hopper, and detecting that the pressure PI-1 of the weighing hopper is an atmospheric pressure value by a pressure gauge 20 above the weighing hopper;
(3) closing the gate valve XV-3, weighing the adipic acid in a weighing hopper, and enabling the feeding amount of the adipic acid to reach a set value;
(4) opening an emptying valve XV-2 above the intermediate hopper, closing a gate valve XV-7, and detecting that the intermediate hopper PI-2 is at an atmospheric pressure value by a pressure gauge 21 above the intermediate hopper;
(5) the adipic acid enters an intermediate hopper;
(6) closing the gate valve XV-19, opening the regulating valve XV-11, and controlling the pressure in the intermediate hopper to reach a set value;
(7) closing the regulating valve XV-11, opening the nitrogen regulating valve XV-17, and filling nitrogen;
(8) when the pressure of the pre-esterification reaction kettle reaches a set value, closing a nitrogen regulating valve XV-17;
(9) opening a methanol feed valve XV-12, and closing the methanol feed valve XV-12 after the designed flow of methanol is reached;
(10) opening a gate valve XV-7, conveying materials by a screw conveyor, and feeding adipic acid through a rotary valve;
(11) stirring, reacting, sampling, discharging the materials in the pre-esterification reaction kettle to a pre-esterification buffer tank after the acid value reaches the standard.
A gate valve XV-3 is arranged at an outlet at the bottom of the weighing hopper; a gate valve XV-19 is arranged between the outlet at the bottom of the middle hopper and the rotary valve; the top parts of the weighing hopper and the middle hopper are provided with dust removing equipment; a pipeline for removing a torch is arranged at the top of the pre-esterification buffer tank; a gate valve XV-7 is arranged on a pipeline between the screw conveyor and the pre-esterification reaction kettle. The nitrogen pipeline is connected with the intermediate hopper and the pre-esterification reaction kettle. The operating conditions of the pre-esterification reaction kettle meet the following requirements: the wall temperature is not less than 130 ℃, the dissolving time is not less than 60min, and when the solution temperature exceeds 82 ℃, the adipic acid is completely dissolved; adipic acid in solution begins to precipitate when the temperature of the solution is less than 70 ℃. The adipic acid and methanol mixed solution is heated to more than 85 ℃ and then is continuously fed, and the temperature of a pipeline and a feeding pump in the whole feeding process is maintained to be more than 85 ℃.
The operating conditions of the pre-esterification reaction kettle are as follows: reaction temperature 150 ℃, methanol to adipic acid molar ratio 4: 1, the reaction time is 4 hours, and the reaction pressure is the saturated vapor pressure of the methanol at 150 ℃.
F1(m)＝t*73*M(t)/(80*Y)，F1(m) is the feed of adipic acid (unit: t), t is the residence time of the reaction (unit: h), M (t) is the expected yield of monomethyl adipate per hour (unit: t), and Y is the yield of the monoesterification reaction.
F (T) 10^ 7.87863-1473.11/(T +230) ], F (T) the pressure of the pre-esterification reaction kettle (unit: mmHg) and T the temperature of the methanol feed (unit:. degree. C).
F2(m)＝F1(m)*n*16/73，F2(m) is the feeding amount of methanol, (unit: t), n is the feeding molar ratio of adipic acid and methanol; the feeding amount of the adipic acid and the methanol adopts a ratio control method, a rotary valve is controlled by a ratio controller, and when the methanol is fed, the adipic acid is fed according to a preset molar feeding ratio.
In the above technical scheme, preferably, the pre-esterification reaction kettle adopts external heating, wherein jacketed heating can be replaced by coil tube heating.
In fig. 1, the adipic acid discharge system was operated intermittently and the weighing hopper was designed to be 1 day (24 hours). The solid feeding system is operated intermittently, and the intermediate hopper is designed for feeding materials according to the requirement of 2 hours. The pre-esterification unit adopts intermittent operation, and the pre-esterification reaction kettle is designed according to the reaction liquid amount for dissolving for 0.5 hour. The pre-esterification reaction kettle is heated by jacket steam, and the wall temperature is ensured to be above 150 ℃; circulating methanol from a methanol intermediate tank is pumped into the pre-esterification reaction kettle through a solvent methanol pump. Recycled methanol (4800kg, required for 0.5 h) was added; adding adipic acid solid (5475kg, required amount of 0.5 h) into the pre-esterification reaction kettle through a screw conveyor and a gate valve (double valve), and simultaneously starting a stirring paddle; closing the gate valve after the solid feeding is finished, introducing low-pressure steam into the jacket, heating, and stirring for about one hour until the low-pressure steam is dissolved; after sampling and inspection are qualified, opening a discharge valve, and putting the reaction liquid into a pre-esterification buffer tank; after material returning is finished, filling low-pressure nitrogen to ensure that the solution completely enters the buffer tank, closing the discharge valve, opening the emptying valve, and opening the gate valve to prepare the solution in the next kettle again after the pressure is reduced to normal pressure; and other pre-esterification reaction kettles are repeated according to the steps, so that the methanol solution of the adipic acid in the pre-esterification buffer tank meets the requirement of the subsequent production dosage.
When t is 4h, M (t) is 3t, and Y is 0.5, the feeding amount F of adipic acid1(m)＝21.9t。
When T is 150 ℃, the pressure F (T) is mmHg in the pre-esterification reaction kettle
When F is present1(m) 21.9t, n 4) the amount of methanol fed F2(m)＝19.2t。
[ example 3 ]
A method for automatically controlling adipic acid mono-esterification reaction is disclosed, as shown in figure 1, adipic acid raw material passes through a weighing hopper, an intermediate hopper and a spiral conveyor and then enters a pre-esterification reaction kettle to contact with methanol raw material, the mixture after reaction enters a pre-esterification buffer tank, and the bottom material flow of the pre-esterification buffer tank is sent to a catalytic reaction tower as adipic acid mono-esterification product; the pipeline connecting the middle hopper and the screw conveyer is provided with a rotary valve, the rotary valve is driven by a motor to enable an impeller with an equal-division structure to rotate in the shell, adipic acid in a feeding device at the upper part of the shell is filled in a cavity of the impeller and rotates to the lower part of the shell along with the impeller, and the adipic acid is uniformly and continuously discharged downstream according to the requirement of a conveying system. The rotary valve is controlled by a proportional signal, is associated with a methanol feed flow metering valve, and controls the proportion of raw materials entering the pre-esterification reaction kettle; the automated control process for the adipic acid monoesterification reaction (as shown in FIG. 2) comprises:
(1) starting;
(2) opening an emptying valve XV-1 above the weighing hopper, and detecting that the pressure PI-20 of the weighing hopper is an atmospheric pressure value by a pressure gauge above the weighing hopper;
(3) closing the gate valve XV-3, weighing the adipic acid in a weighing hopper, and enabling the feeding amount of the adipic acid to reach a set value;
(4) opening an emptying valve XV-2 above the intermediate hopper, closing a gate valve XV-7, and detecting that the intermediate hopper PI-21 is at an atmospheric pressure value by a pressure gauge above the intermediate hopper;
(5) the adipic acid enters an intermediate hopper;
(6) closing the gate valve XV-19, opening the regulating valve XV-11, and controlling the pressure in the intermediate hopper to reach a set value;
(7) closing the regulating valve XV-11, opening the nitrogen regulating valve XV-17, and filling nitrogen;
(8) when the pressure of the pre-esterification reaction kettle reaches a set value, closing a nitrogen regulating valve XV-17;
(9) opening a methanol feed valve XV-12, and closing the methanol feed valve XV-12 after the designed flow of methanol is reached;
(10) opening a gate valve XV-7, conveying materials by a screw conveyor, and feeding adipic acid through a rotary valve;
(11) stirring, reacting, sampling, discharging the materials in the pre-esterification reaction kettle to a pre-esterification buffer tank after the acid value reaches the standard.
A gate valve XV-3 is arranged at an outlet at the bottom of the weighing hopper; a gate valve XV-19 is arranged between the outlet at the bottom of the middle hopper and the rotary valve; the top parts of the weighing hopper and the middle hopper are provided with dust removing equipment; a pipeline for removing a torch is arranged at the top of the pre-esterification buffer tank; a gate valve XV-7 is arranged on a pipeline between the screw conveyor and the pre-esterification reaction kettle. The nitrogen pipeline is connected with the intermediate hopper and the pre-esterification reaction kettle. The operating conditions of the pre-esterification reaction kettle meet the following requirements: the wall temperature is not less than 130 ℃, the dissolving time is not less than 60min, and when the solution temperature exceeds 82 ℃, the adipic acid is completely dissolved; adipic acid in solution begins to precipitate when the temperature of the solution is less than 70 ℃. The adipic acid and methanol mixed solution is heated to more than 85 ℃ and then is continuously fed, and the temperature of a pipeline and a feeding pump in the whole feeding process is maintained to be more than 85 ℃.
The operating conditions of the pre-esterification reaction kettle are as follows: reaction temperature 140 ℃, methanol to adipic acid molar ratio 3.5: 1, the reaction time is 3 hours, and the reaction pressure is the saturated vapor pressure of the methanol at 140 ℃.
F1(m)＝t*73*M(t)/(80*Y)，F1(m) is the feed of adipic acid (unit: t), t is the residence time of the reaction (unit: h), M (t) is the expected yield of monomethyl adipate per hour (unit: t), and Y is the yield of the monoesterification reaction.
F (T) 10^ 7.87863-1473.11/(T +230) ], F (T) the pressure of the pre-esterification reaction kettle (unit: mmHg) and T the temperature of the methanol feed (unit:. degree. C).
F2(m)＝F1(m)*n*16/73，F2(m) is the feeding amount of methanol, (unit: t), n is the feeding molar ratio of adipic acid and methanol; the feeding amount of the adipic acid and the methanol adopts a ratio control method, a rotary valve is controlled by a ratio controller, and when the methanol is fed, the adipic acid is fed according to a preset molar feeding ratio.
In the above technical scheme, preferably, the pre-esterification reaction kettle adopts external heating, wherein jacketed heating can be replaced by coil tube heating.
In fig. 1, the adipic acid discharge system was operated intermittently and the weighing hopper was designed to be 1 day (24 hours). The solid feeding system is operated intermittently, and the intermediate hopper is designed for feeding materials according to the requirement of 2 hours. The pre-esterification unit adopts intermittent operation, and the pre-esterification reaction kettle is designed according to the reaction liquid amount for dissolving for 0.5 hour. The pre-esterification reaction kettle is heated by jacket steam, and the wall temperature is ensured to be above 140 ℃; circulating methanol from a methanol intermediate tank is pumped into the pre-esterification reaction kettle through a solvent methanol pump. Add circulating methanol (3150kg, required for 0.5 h); adipic acid solid (4100kg, required amount of 0.5 h) is added into the pre-esterification reaction kettle through a screw conveyor and a gate valve (double valve), and simultaneously a stirring paddle is started; closing the gate valve after the solid feeding is finished, introducing low-pressure steam into the jacket, heating, and stirring for about one hour until the low-pressure steam is dissolved; after sampling and inspection are qualified, opening a discharge valve, and putting the reaction liquid into a pre-esterification buffer tank; after material returning is finished, filling low-pressure nitrogen to ensure that the solution completely enters the buffer tank, closing the discharge valve, opening the emptying valve, and opening the gate valve to prepare the solution in the next kettle again after the pressure is reduced to normal pressure; and other pre-esterification reaction kettles are repeated according to the steps, so that the methanol solution of the adipic acid in the pre-esterification buffer tank meets the requirement of the subsequent production dosage.
When t is 3h, m (t) is 3t, and Y is 0.5, the feeding amount F of adipic acid1(m)＝16.4t。
When T is 140 ℃, the pressure F (T) is 7893.18mmHg in the pre-esterification reaction kettle
When F is present1When (m) is 16.4t and n is 3.5, the amount of methanol fed F2(m)＝12.6t。
At present, the prior adipic acid mono-esterification production process mainly comprises two types of batch esterification and batch feeding mono-esterification. The continuous production is not realized in the feeding process, the operation process is complex, more manpower is occupied, certain danger is realized, and the process energy consumption is high. Obviously, the method of the invention has great technical advantages.
Claims (1)
1. A method for automatically controlling adipic acid mono-esterification reaction comprises the steps that adipic acid raw materials enter a pre-esterification reaction kettle after passing through a weighing hopper, an intermediate hopper and a spiral conveyor, the adipic acid raw materials are contacted with a methanol raw material, a mixture after reaction enters a pre-esterification buffer tank, and material flow at the bottom of the pre-esterification buffer tank is sent to a catalytic reaction tower as an adipic acid mono-esterification product; wherein, a pipeline connecting the intermediate hopper and the screw conveyor is provided with a rotary valve, and the rotary valve is controlled by a proportional signal and is associated with a methanol feed flow metering valve to control the proportion of raw materials entering the pre-esterification reaction kettle; the automatic control process of the adipic acid mono-esterification reaction comprises the following steps:
(1) starting;
(2) opening an emptying valve XV-1 above the weighing hopper, and detecting that the pressure PI-1 of the weighing hopper is an atmospheric pressure value by a pressure gauge 20 above the weighing hopper;
(3) closing the gate valve XV-3, weighing the adipic acid in a weighing hopper, and enabling the feeding amount of the adipic acid to reach a set value;
(4) opening an emptying valve XV-2 above the intermediate hopper, closing a gate valve XV-7, and detecting that the intermediate hopper PI-2 is at an atmospheric pressure value by a pressure gauge 21 above the intermediate hopper;
(5) the adipic acid enters an intermediate hopper;
(6) closing the gate valve XV-19, opening the regulating valve XV-11, and controlling the pressure in the intermediate hopper to reach a set value;
(7) closing the regulating valve XV-11, opening the nitrogen regulating valve XV-17, and filling nitrogen;
(8) when the pressure of the pre-esterification reaction kettle reaches a set value, closing a nitrogen regulating valve XV-17;
(9) opening a methanol feed valve XV-12, and closing the methanol feed valve XV-12 after the designed flow of methanol is reached;
(10) opening a gate valve XV-7, conveying materials by a screw conveyor, and feeding adipic acid through a rotary valve;
(11) stirring, reacting, sampling, discharging the materials in the pre-esterification reaction kettle to a pre-esterification buffer tank after the acid value reaches the standard;
a gate valve XV-3 is arranged at an outlet at the bottom of the weighing hopper; a gate valve XV-19 is arranged between the outlet at the bottom of the middle hopper and the rotary valve; the top parts of the weighing hopper and the middle hopper are provided with dust removing equipment; a pipeline for removing a torch is arranged at the top of the pre-esterification buffer tank; a gate valve XV-7 is arranged on a pipeline between the spiral conveyor and the pre-esterification reaction kettle; the rotary valve is driven by a motor to enable an impeller with an equal-division structure to rotate in the shell, adipic acid in a feeding device at the upper part of the shell is filled in a cavity of the impeller and rotates to the lower part of the shell along with the impeller, and the adipic acid is uniformly, continuously and downstream discharged according to the requirement of a conveying system; the nitrogen pipeline is connected with the intermediate hopper and the pre-esterification reaction kettle; the operating conditions of the pre-esterification reaction kettle meet the following requirements: the wall temperature is not less than 130 ℃, the dissolving time is not less than 60min, and when the solution temperature exceeds 82 ℃, the adipic acid is completely dissolved; when the temperature of the solution is less than 70 ℃, adipic acid in the solution begins to separate out; heating the mixed solution of adipic acid and methanol to above 85 ℃, and then continuously feeding, wherein the temperature of a pipeline and a feeding pump in the whole feeding process is maintained above 85 ℃; the operating conditions of the pre-esterification reaction kettle are as follows: the reaction temperature is 130-150 ℃, and the molar ratio of methanol to adipic acid is 3-4: 1, the reaction time is 2-4 h, and the reaction pressure is 130ESaturated vapor pressure at 150 ℃; f1(m) ═ t 73 × m (t)/(80 × Y), F1(m) is the feed rate of adipic acid, t; t is the residence time of the reaction, h; m (t) is the expected yield of monomethyl adipate per hour, t; y is the yield of the mono-esterification reaction; f (T) 10^ 7.87863-1473.11/(T +230)]F (T) is the pressure of the pre-esterification reaction kettle and mmHg; t is the feed temperature of methanol, DEG C; f2(m)＝F1(m)*n*16/73，F2(m) is the feed amount of methanol, t; n is the feed molar ratio of adipic acid to methanol; the feeding amount of adipic acid and methanol adopts a ratio control method, a rotary valve is controlled by a ratio controller, and when methanol is fed, adipic acid is fed according to a preset molar feeding ratio; the pre-esterification reaction kettle adopts external heating, wherein jacket type heating can be replaced by coil type heating.
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Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS60120839A (en) * | 1983-12-02 | 1985-06-28 | Nippon Ester Co Ltd | Method for continuous supply of slurry of terephthalic acid and ethylene glycol |
| RO103911B1 (en) * | 1989-07-31 | 1994-06-20 | Centrul De Cercetari Pentru Fi | Production method of monomethyl-adipate |
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Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS60120839A (en) * | 1983-12-02 | 1985-06-28 | Nippon Ester Co Ltd | Method for continuous supply of slurry of terephthalic acid and ethylene glycol |
| RO103911B1 (en) * | 1989-07-31 | 1994-06-20 | Centrul De Cercetari Pentru Fi | Production method of monomethyl-adipate |
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