System and method for recycling ethylene oxide in continuous production of ethephon

Abstract

The invention relates to the technical field of organic chemistry, in particular to a system and method for recycling ethylene oxide in continuous production of ethephon, the system comprises a preheater, a nitrogen source, a stripping tower, a condensation assembly, a tail gas treatment device, an esterification reaction kettle, an EO destroying device and a cooler, the preheater is communicated with a feed valve before entering a rearrangement kettle, the stripping tower is connected with the preheater, and the condensation assembly is connected with the cooler. The condensation assembly and the cooler are both connected with the stripping tower, the tail gas treatment equipment is connected with the condensation assembly, the esterification reaction kettle and the EO breaking equipment are also connected with the condensation assembly, the cooler is further connected with the rearrangement kettle, and the nitrogen source is communicated with the bottom of the preheater. In this way, the technical problems that in the prior art, ethylene oxide contained in ethephon production is insufficient in recycling and high in cost are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of organic chemistry, and particularly to a system and method for recycling and reusing ethylene oxide in the continuous production of ethephon. Background Art

[0002] Ethephon is a plant growth regulator, which has the physiological effects of promoting latex secretion in plants, accelerating ripening, shedding, senescence, and promoting flowering, and is usually used as an agricultural plant growth stimulant. In the production of ethephon, excessive ethylene oxide reacts with phosphorus trichloride, and ethephon is produced through steps such as esterification, rearrangement, and acidolysis. Excessive ethylene oxide not only increases the production cost, but also affects the quality of ethephon, reduces the yield of ethephon, and increases the burden on the waste gas treatment device.

[0003] Currently, the main treatment methods for ethylene oxide contained in triester include: 1. Stripping method: Before the triester enters the rearrangement kettle, nitrogen is used to carry away the ethylene oxide in the triester through equipment such as a stripping tower, and then enters the subsequent tail gas device for incineration treatment. The stripped triester continues to enter the rearrangement kettle for rearrangement reaction. 2. Stripping + sulfuric acid hydrolysis breaking method. Before the triester enters the rearrangement kettle, nitrogen is used to carry away the ethylene oxide in the triester through a stripping tower, and the gas phase enters the sulfuric acid tower. Under acidic conditions, ethylene oxide is hydrolyzed into ethylene glycol, thereby reducing the content of ethylene oxide in the triester. This process generates a large amount of COD wastewater, increasing the sewage treatment cost. Excessive ethylene oxide is not effectively recycled, resulting in waste and increased production cost. 3. Stripping + organic solvent absorption method: Before the triester enters the rearrangement kettle, nitrogen is introduced at the bottom of the stripping tower, and an organic solvent is sprayed at the top, so as to absorb the ethylene oxide in the triester into the solvent, reducing the content of ethylene oxide in the triester. This method only converts ethylene oxide from the gas phase to the solvent. This process requires additional addition of solvent, and ethylene oxide cannot be recycled, increasing the pressure of hazardous waste treatment.

[0004] In summary, in the prior art, there are problems of insufficient recycling and high cost in the treatment method of ethylene oxide contained in the production of ethephon. Summary of the Invention

[0005] The purpose of the present invention is to provide a system and method for recycling and reusing ethylene oxide in the continuous production of ethephon, aiming to solve the technical problems of insufficient recycling and high cost in the treatment method of ethylene oxide contained in the production of ethephon in the prior art.

[0006] To achieve the above object, an ethylene oxide recovery and reuse system in the continuous production of ethephon of the present invention includes a preheater, a nitrogen source, a stripping column, a condensation assembly, a tail gas treatment device, an esterification reaction kettle, an EO destruction device, and a cooler. The preheater is connected to the feed valve before entering the rearrangement kettle. The stripping column is connected to the preheater. The condensation assembly and the cooler are both connected to the stripping column. The tail gas treatment device is connected to the condensation assembly. The esterification reaction kettle and the EO destruction device are also both connected to the condensation assembly. The cooler is further connected to the rearrangement kettle. The nitrogen source is connected to the bottom of the preheater.

[0007] Among them, the ethylene oxide recovery and reuse system in the continuous production of ethephon further includes a transfer pump, and the transfer pump is arranged between the esterification reaction kettle and the condensation assembly.

[0008] Among them, the condensation assembly includes a first condenser and a second condenser. The first condenser is connected to the stripping column. The second condenser is connected to the first condenser. The tail gas treatment device is connected to the second condenser. The EO destruction device is connected to both the first condenser and the second condenser. Similarly, the esterification reaction kettle is connected to both the first condenser and the second condenser.

[0009] The present invention also provides a method for recovering and reusing ethylene oxide in the continuous production of ethephon, which is applied to the ethylene oxide recovery and reuse system in the continuous production of ethephon as described above.

[0010] It includes the following steps:

[0011] First, the triester from the feed valve before entering the rearrangement kettle is heated by the heat transfer oil in the preheater, and then enters the stripping column.

[0012] Nitrogen is introduced into the bottom of the stripping column through the nitrogen source for stripping, so that EO and DCE in the triester are stripped out by nitrogen.

[0013] The stripping gas is recycled to the esterification reaction kettle or the EO destruction device through the condenser. The tail gas containing nitrogen and a small amount of EO&DCE enters the tail gas treatment device. After the liquid phase is stripped and cooled by the triester cooler, it flows into the rearrangement kettle by gravity.

[0014] Among them, before the recovery and reuse, a pre-start-up inspection needs to be carried out to ensure that the pipelines between the devices are unobstructed, the valves are flexible, and there are no leakage points.

[0015] Among them, after the pre-start-up inspection is completed, the manual valve of the stripping column gas phase pipeline to the tail gas treatment device is opened.

[0016] Open the manual valve between the liquid phase of the stripping column and the rearrangement kettle, open the manual valve between the preheater and the stripping column, and open the manual valve on the nitrogen pipeline of the stripping column;

[0017] Open the nitrogen switch valve of the stripping column, control the nitrogen inlet pressure of the stripping column within the specified range through the regulating valve, and control the nitrogen flow rate of the stripping column by adjusting the nitrogen valve.

[0018] Among them, before the triester enters the preheater, open the manual valves for the inlet and outlet of the heat transfer oil of the preheater, open the heat transfer oil switch valve, control the outlet temperature of the preheater by adjusting the opening of the heat transfer oil regulating valve. When the outlet temperature of the preheater reaches the set temperature, open the triester feed switch valve of the preheater and control the triester feed rate.

[0019] In a system and method for recycling ethylene oxide in the continuous production of ethephon according to the present invention, during specific use, first, the triester from behind the feed valve before entering the rearrangement kettle is heated by the heat transfer oil in the preheater, and then enters the stripping column; nitrogen is introduced into the bottom of the stripping column through the nitrogen source for stripping, so that EO and DCE in the triester are stripped out by nitrogen; the stripping gas is recycled to the esterification reaction kettle or the EO destruction equipment through the condenser, and the tail gas containing nitrogen and a small amount of EO & DCE enters the tail gas treatment equipment. After the liquid phase is stripped and cooled by the triester cooler, it flows into the rearrangement kettle by gravity. In this way, the technical problems of insufficient recycling and high cost in the existing treatment method of ethylene oxide contained in the production of ethephon are solved;

[0020] After nitrogen stripping in the present invention, the gas phase containing ethylene oxide passes through the first condenser and the second condenser, and the condensed liquid containing ethylene oxide is directly recycled to the esterification reaction kettle.

[0021] The present invention has the following beneficial effects:

[0022] 1. The content of EO in the triester is less than 0.1%;

[0023] 2. The excessive EO in the triester is recycled and reused in the system, reducing the output of three wastes, increasing the ethephon yield, and further reducing the production cost;

[0024] 3. Improve the product quality and enhance the product competitiveness. Description of the Drawings

[0025] 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 for use in the description of the embodiments or the prior art. 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.

[0026] Figure 1 It is the schematic diagram of the ethylene oxide recovery and reuse system in the continuous production of ethephon of the present invention.

[0027] 1 - Preheater, 2 - Nitrogen source, 3 - Stripping column, 4 - Tail gas treatment equipment, 5 - Esterification reaction kettle, 6 - EO destruction equipment, 7 - Cooler, 8 - Transfer pump, 9 - First condenser, 10 - Second condenser. Detailed implementation manners

[0028] The following will describe in detail the embodiments of the present invention. The examples of the embodiments are shown in the drawings. The embodiments described below with reference to the drawings are exemplary and are intended to explain the present invention, and should not be construed as a limitation to the present invention.

[0029] Please refer to Figure 1 , Figure 1 It is the schematic diagram of the ethylene oxide recovery and reuse system in the continuous production of ethephon of the present invention.

[0030] The present invention provides an ethylene oxide recovery and reuse system in the continuous production of ethephon, including a preheater 1, a nitrogen source 2, a stripping column 3, a condensation assembly, a tail gas treatment equipment 4, an esterification reaction kettle 5, an EO destruction equipment 6, and a cooler 7. The preheater 1 is connected to the feed valve before entering the rearrangement kettle. The stripping column 3 is connected to the preheater 1. The condensation assembly and the cooler 7 are both connected to the stripping column 3. The tail gas treatment equipment 4 is connected to the condensation assembly. The esterification reaction kettle 5 and the EO destruction equipment 6 are also both connected to the condensation assembly. The cooler 7 is further connected to the rearrangement kettle. The nitrogen source 2 is connected to the bottom of the preheater 1.

[0031] The ethylene oxide recovery and reuse system in the continuous production of ethephon further includes a transfer pump 8, and the transfer pump 8 is arranged between the esterification reaction kettle 5 and the condensation assembly.

[0032] The condensation assembly includes a first condenser 9 and a second condenser 10. The first condenser 9 is connected to the stripping column 3. The second condenser 10 is connected to the first condenser 9. The tail gas treatment equipment 4 is connected to the second condenser 10. The EO destruction equipment 6 is connected to both the first condenser 9 and the second condenser 10. Similarly, the esterification reaction kettle 5 is connected to both the first condenser 9 and the second condenser 10.

[0033] For this specific embodiment, during specific use, first, the triester after the feed valve before entering the rearrangement kettle is heated by the heat transfer oil in the preheater 1, and then enters the stripping tower 3; nitrogen is introduced into the bottom of the stripping tower 3 through the nitrogen source 2 for stripping, so that EO and DCE in the triester are stripped out by the nitrogen; the stripping gas is recycled to the esterification reactor 5 or the EO destruction device 6, and the tail gas containing nitrogen and a small amount of EO&DCE enters the tail gas treatment device 4. After the liquid phase is stripped, it is cooled by the triester cooler 7 and then flows into the rearrangement kettle by gravity. After nitrogen stripping in the present invention, the gas phase containing ethylene oxide passes through the first condenser 9 and the second condenser 10, and the condensate containing ethylene oxide is directly recycled to the esterification reactor 5. In this way, the technical problems of insufficient recycling and high cost in the treatment method of ethylene oxide contained in the production of ethephon in the prior art are solved.

[0034] The present invention also provides a method for recycling and reusing ethylene oxide in the continuous production of ethephon, which is applied to the system for recycling and reusing ethylene oxide in the continuous production of ethephon as described above.

[0035] It includes the following steps:

[0036] S1. First, the triester after the feed valve before entering the rearrangement kettle is heated by the heat transfer oil in the preheater 1, and then enters the stripping tower 3;

[0037] For this specific embodiment, before recycling and reuse, pre-start checks are required. Check whether the public utilities of water, electricity, and gas are supplied normally, and the indicators such as temperature and pressure should meet the process requirements; check the preheater 1, the stripping tower 3, pipelines, valves, sight glasses, etc., to ensure that the pipelines are unobstructed, the valves are flexible, and there are no leakage points; check that all electrical instruments are normal, and turn on the instrument air for the regulating valve; assist the instrument worker to check that the DCS system, automatic control instruments, and on-site instruments are all normal and in good condition, etc.

[0038] Subsequently, open the manual valve between the liquid phase of the stripping tower 3 and the rearrangement kettle, open the manual valve between the preheater 1 and the stripping tower 3, and open the manual valve on the nitrogen pipeline of the stripping tower 3;

[0039] Open the nitrogen switch valve of the stripping tower 3, control the nitrogen inlet pressure of the stripping tower 3 within the specified range through the regulating valve, and control the nitrogen flow rate of the stripping tower 3 by adjusting the nitrogen valve.

[0040] Open the manual valves at the inlet and outlet of the heat transfer oil of the preheater 1, open the heat transfer oil switch valve, control the outlet temperature of the preheater 1 by adjusting the opening of the heat transfer oil regulating valve. When the outlet temperature of the preheater 1 reaches the set temperature, open the triester feed switch valve of the preheater 1 and control the triester feed rate.

[0041] S2. Nitrogen is introduced into the bottom of the stripping column 3 through the nitrogen source 2 for stripping, so that EO and DCE in the triester are stripped out by the nitrogen.

[0042] S3. Sampling and analysis are carried out, and then recycling or destruction is performed.

[0043] For this specific embodiment, sampling is carried out through the sampling valve, and the material destination is determined according to the test results. When the liquid level of the condensate in the receiving pipe reaches 600, all the manual valves at the inlet and outlet of the metering pump P5-801A are opened. If the inspection is qualified, it goes to the esterification reactor 5. The manual valve of the pipeline from the metering pump to the esterification reactor 5 is opened, the manual valve of the pipeline from the metering pump to the receiving tank is closed, the corresponding switch valves and the front and rear manual valves are opened, and the flow rate is controlled within a certain range by adjusting the frequency of the metering pump. After being recycled a certain number of times, the condensate goes to the DCE receiving tank. The manual valve of the pipeline from the metering pump to the receiving tank is opened, the manual valve of the pipeline from the metering pump to the esterification reactor 5 is closed, the switch valve and the front and rear manual valves are opened, and the flow rate is controlled within a certain range by adjusting the frequency of the metering pump. After the batch treatment, the operation of going to the esterification reactor 5 is restored.

[0044] The main control parameters of the present invention are as follows:

[0045]

[0046] When using the ethylene phosphonic acid continuous production ethylene oxide recovery and recycling system and method of the present invention, in specific use, first, the triester from behind the feed valve before entering the rearrangement kettle is heated by the heat transfer oil in the preheater 1, and then enters the stripping column 3; nitrogen is introduced into the bottom of the stripping column 3 through the nitrogen source 2 for stripping, so that EO and DCE in the triester are stripped out by the nitrogen; the stripping gas is recycled to the esterification reactor 5 or the EO destruction device 6 through the condenser, and the tail gas containing nitrogen and a small amount of EO & DCE enters the tail gas treatment device 4. After the liquid phase is stripped, it is cooled by the triester cooler 7 and then flows into the rearrangement kettle by gravity. In this way, the technical problems of insufficient recycling and high cost in the treatment method of ethylene oxide contained in the production of ethylene phosphonic acid in the prior art are solved;

[0047] After nitrogen stripping in the present invention, the gas phase containing ethylene oxide passes through the first condenser 9 and the second condenser 10, and the condensate containing ethylene oxide is directly recycled to the esterification reactor 5.

[0048] The present invention has the following beneficial effects:

[0049] 1. The content of EO in the triester is less than 0.1%;

[0050] 2. The excessive EO in the triester is recovered and reused, circulating and reused in the system. This reduces the generation of three wastes, improves the yield of ethephon, and further reduces production costs;

[0051] 3. Improve product quality and competitiveness.

[0052] The above-disclosed is only a preferred embodiment of the present invention. Of course, the scope of the rights of the present invention cannot be limited thereby. Those of ordinary skill in the art can understand all or part of the processes of implementing the above embodiments, and the equivalent changes made according to the claims of the present invention still fall within the scope covered by the invention.

Claims

1. An ethylene phosphonic acid continuous production ethylene oxide recovery and reuse system, characterized in that it includes a preheater, a nitrogen source, a stripping column, a condensation assembly, a tail gas treatment device, an esterification reaction kettle, an EO destruction device and a cooler. The preheater is connected to the feed valve before entering the rearrangement kettle. The stripping column is connected to the preheater. The condensation assembly and the cooler are both connected to the stripping column. The tail gas treatment device is connected to the condensation assembly. The esterification reaction kettle and the EO destruction device are also both connected to the condensation assembly. The cooler is also connected to the rearrangement kettle. The nitrogen source is connected to the bottom of the preheater.

2. The ethylene phosphonic acid continuous production ethylene oxide recovery and reuse system according to claim 1, characterized in that the ethylene phosphonic acid continuous production ethylene oxide recovery and reuse system further includes a transfer pump, and the transfer pump is arranged between the esterification reaction kettle and the condensation assembly.

3. The ethylene phosphonic acid continuous production ethylene oxide recovery and reuse system according to claim 2, characterized in that the condensation assembly includes a first condenser and a second condenser. The first condenser is connected to the stripping column. The second condenser is connected to the first condenser. The tail gas treatment device is connected to the second condenser. The EO destruction device is connected to both the first condenser and the second condenser. Similarly, the esterification reaction kettle is connected to both the first condenser and the second condenser.

4. An ethylene phosphonic acid continuous production ethylene oxide recovery and reuse method, applied to the ethylene phosphonic acid continuous production ethylene oxide recovery and reuse system according to claim 3, characterized in that it includes the following steps: First, the triester from the feed valve before entering the rearrangement kettle is heated by the heat transfer oil in the preheater, and then enters the stripping column; Nitrogen is introduced into the bottom of the stripping column through the nitrogen source for stripping, so that EO and DCE in the triester are stripped out by nitrogen; The stripped gas is recycled to the esterification reaction kettle or the EO destruction device through the condenser. The tail gas containing nitrogen and a small amount of EO&DCE enters the tail gas treatment device. After the liquid phase is stripped and cooled by the triester cooler, it flows into the rearrangement kettle by gravity.

5. The ethylene phosphonic acid continuous production ethylene oxide recovery and reuse method according to claim 4, characterized in that Before the recovery and reuse, a pre-start inspection is required to ensure that the pipelines between the devices are unobstructed, the valves are flexible, and there are no leakage points.

6. The ethylene phosphonic acid continuous production ethylene oxide recovery and reuse method according to claim 5, characterized in that After the pre-start inspection is completed, open the manual valve of the stripping column gas phase pipeline to the tail gas treatment device; Open the manual valve between the stripping column liquid phase and the rearrangement kettle, open the manual valve between the preheater and the stripping column, and open the manual valve on the stripping column nitrogen pipeline; Open the nitrogen switch valve of the stripping column, control the nitrogen inlet pressure of the stripping column within the specified range through the regulating valve, and control the nitrogen flow rate of the stripping column by adjusting the nitrogen valve.

7. The ethylene phosphonic acid continuous production ethylene oxide recovery and reuse method according to claim 6, characterized in that Before the triester enters the preheater, open the hand valves for the inlet and outlet of the heat transfer oil of the preheater, open the heat transfer oil switch valve, control the outlet temperature of the preheater by adjusting the opening degree of the heat transfer oil regulating valve. When the outlet temperature of the preheater reaches the set temperature, open the triester feed switch valve of the preheater and control the triester feed rate.

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