CN218590140U - Phosgene recovery unit in isocyanate production process - Google Patents

Abstract

The utility model provides a phosgene recovery unit in isocyanate production process, relates to phosgene and retrieves technical field, including the absorption tower cauldron, the top and the bottom of absorption tower cauldron are provided with respectively and collect mouth and pay-off mouth, and absorption tower cauldron is inside to be provided with the backward flow unit, and the upper portion of recovery unit is provided with sprays the structure, and the backward flow unit includes distribution shower nozzle, condensation spare and the recovery dish that top-down set gradually, distributes and is connected through the back flow between shower nozzle and the recovery dish. Therefore, the beneficial effects of the utility model are that: the combination of one-level condensation subassembly, second grade condensation subassembly and spray thrower for this device utilizes the solvent to fully absorb phosgene through the mode of fractional condensation, thereby has made things convenient for HCl and phosgene can the abundant separation.

Description

Phosgene recovery unit in isocyanate production process

Technical Field

The utility model relates to a technical field, in particular to phosgene recovery unit in isocyanate production process are retrieved to phosgene.

Background

The existing phosgene synthesis is mainly a gas-phase phosgene method for preparing isocyanate, but the gas-phase phosgene method can generate a large amount of HCl (hydrogen chloride) gas and excessive phosgene. In order to improve the economic benefit, phosgene is recovered, so that the separation of phosgene and HCl is important.

Because the HCl carried in the recovered phosgene and the amine can generate ammonium salt to block a reaction device when being fed, the prior method mainly separates the HCl by condensing the phosgene or separates the mixed gas by pressurizing and absorbing the mixed gas. However, the absorption of pressure can generate a significant source of danger, and devices with high light and high pressure increase the uncertainty of the danger; phosgene condensation mainly faces the situation that HCl is difficult to separate, because solvent used for phosgene condensation has a good effect on absorbing phosgene, and liquid light after condensation has a good absorption capacity on HCl, a certain amount of HCl is changed into gas light to enter a reaction area after entering the next stage along with the liquid light, and because the purity of the liquid light is improved in the next stage, the separation of HCl is more difficult, and HCl is finally brought into the reaction area to influence the yield.

In view of the above, the prior art has the problem that HCl and phosgene are difficult to separate, and therefore the prior art separation device has obvious inconvenience and defects in practical use, and therefore needs to be improved.

SUMMERY OF THE UTILITY MODEL

To above defect, the utility model aims at providing a phosgene recovery unit in isocyanate production process, the problem of HCl and phosgene separation difficulty in the purpose is solved current problem.

In order to realize the purpose, the technical scheme of the utility model is that:

the phosgene recovery device in the production process of isocyanate comprises an absorption tower kettle, wherein the top and the bottom of the absorption tower kettle are respectively provided with a collecting port and a feeding port, a backflow unit is arranged inside the absorption tower kettle, the upper part of the backflow unit is provided with a spraying structure, the backflow unit comprises a distribution spray head, a condensation piece and a recovery disc which are sequentially arranged from top to bottom, and the distribution spray head is connected with the recovery disc through a backflow pipe.

The reflux units are divided into two groups, and the two groups of reflux units are sequentially distributed in the absorption tower from top to bottom.

Wherein, be provided with the micro-pump machine in the recovery dish, the back flow is connected with the micro-pump machine.

Wherein, be provided with the condensation subassembly between spraying structure and the collection mouth, the condensation subassembly includes a plurality of closely arranged heat exchange tube.

The absorption tower comprises an absorption tower kettle, a gas-liquid separator, a liquid separation valve, a sprayer, a preheater and a spraying device, wherein the spraying analysis tower is arranged on one side of the absorption tower kettle, the gas-liquid separator and the liquid separation valve are respectively arranged at the top and the bottom of the spraying analysis tower, the sprayer is arranged between the liquid separation valve and the gas-liquid separator, the preheater is arranged between the sprayer and the liquid separation valve, and two ends of the preheater are respectively connected with the liquid separation valve and the sprayer.

Wherein, be provided with the condenser between branch liquid valve and the spray thrower, the both ends of condenser respectively with divide liquid valve, spray structural connection.

And a demister is arranged between the sprayer and the gas-liquid separator and covers the sprayer.

Wherein the sprayer comprises a plurality of spraying heads spraying upwards.

Wherein, the analysis tower that sprays includes first tower body and second tower body, the second tower body is located the inside of first tower body, it has the heat preservation to fill between second tower body and the first tower body.

An object of the utility model is to provide a phosgene recovery unit in isocyanate production process, after having adopted above-mentioned technical scheme, the beneficial effects of the utility model are that:

firstly, for convenient separation phosgene and HCl, the absorption tower cauldron has been introduced to this scheme, and for effectively retrieving phosgene, the analytic tower that sprays has been introduced again to this scheme. The method avoids the absorption and analysis mode of high temperature and high pressure in the traditional mode, improves the safety, reduces the energy waste, fully separates HCl and phosgene, and avoids the phenomenon that phosgene reacts with amine substances to form ammonium salt to block a reaction device when in use.

And secondly, the combination of the two groups of reflux units and the spraying structure ensures that the device fully absorbs phosgene by utilizing a solvent in a fractional condensation mode, thereby facilitating the full separation of HCl and phosgene.

And thirdly, the existence of the condensation component enables the mist agent contained in the HCl to be condensed and recovered, thereby realizing the full separation of the HCl and the phosgene.

Fourthly, the recovery disc is combined with a micro pump and a distribution nozzle, so that the solvent containing phosgene generates turbulence, HCl contained in the solvent is released, and impurities in the solvent are reduced.

Fifthly, the phosgene is preheated by a preheater to reach the bubble point temperature, thereby facilitating the separation of the phosgene and the solvent.

Sixthly, the existence of the condenser enables the solvent to be reused after being condensed, and waste is reduced.

And the existence of the gas-liquid separator enables the solvent in the phosgene to be separated, so that the phosgene can be obtained in a purer way.

Drawings

FIG. 1 is a view showing the structure of an absorption column bottom;

FIG. 2 is a block diagram of a spray stripper;

FIG. 3 is a schematic diagram of a phosgene recovery apparatus.

In the figure: 10-absorption tower kettle, 11-feeding port, 12-collecting port, 13-reflux unit, 131-distribution spray head, 132-condensation structure, 133-recovery disc, 134-reflux pipe, 135-micro pump machine, 14-spraying structure, 15-condensation component, 26-discharge port, 27-discharge pipeline, 30-spraying analysis tower, 31-gas-liquid separator, 32-liquid separation valve, 33-sprayer, 34-preheater, 35-condenser, 36-demister, 37-spray head, 38-first tower body, 39-second tower body and 40-heat preservation layer.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the invention.

As shown in fig. 1-3, because the traditional method of absorbing the mixed gas by pressurization has a great risk problem, the scheme adopts a condensation absorption method, that is, a phosgene recovery device in the isocyanate production process includes an absorption tower kettle 10, the top and the bottom of the absorption tower kettle 10 are respectively provided with a collection port 12 and a feeding port 11, a reflux unit 13 is arranged inside the absorption tower kettle 10, the upper part of the reflux unit 13 is provided with a spraying structure 14, the reflux unit 13 includes a distribution nozzle 131, a condensation member 132 and a recovery tray 133 which are sequentially arranged from top to bottom, and the distribution nozzle 131 is connected with the recovery tray 133 through a reflux pipe 134. The working principle of the device is as follows: first, the condensing member 132 is pre-cooled, and when the temperature of the condensing member 132 itself drops to a certain range, the feeding is started. The mixed gas of phosgene and HCl gas enters the absorption tower kettle 10 through the feeding port 11, and then the mixed gas moves towards the collecting port 12. Then, the spray structure 14 starts spraying the solvent. Wherein phosgene is readily soluble in the above-mentioned sprayed solvent and HCl gas is not readily soluble in the solvent. After the sprayed solvent and the mixed gas meet at the condensing member 132, phosgene is rapidly absorbed by the solvent and drops with the solvent, and HCl gas is separated and discharged from the collecting port 12. Although HCl gas is not readily soluble in the above solvents, there is still a small portion of HCl gas absorbed by the solvent, and in order to separate this portion of the impurities, the present solution introduces a recovery tray 133. The solvent droplets reach the recovery tray 133 after absorbing phosgene, when the solvent liquid in the recovery tray 133 reaches a certain height, the solvent reaches the distribution nozzle 131 along with the return pipe 134, and then the distribution nozzle 131 sprays the liquid again. Since the less the solvent, the poorer its ability to absorb HCl gas, the solvent in the state of droplets will release part of the HCl gas. Furthermore, when the solvent in the recovery tray 134 enters the return pipe 131, due to the small pipe diameter of the return pipe 131, the solvent may form a turbulent phenomenon during the entering process, which also causes a part of the HCl gas to be released. Therefore, after the solvent is separated by the recovery pan 133, the absorption of HCl gas in the solvent is greatly reduced, and the purity of phosgene is greatly increased.

In this embodiment, the spray structure 14 includes a spray header and a feed pipe 17, and the feed pipe 17 is used for feeding the solvent to the spray header.

The reflux units 13 are two groups, and the two groups of reflux units 13 are sequentially distributed in the absorption tower kettle 10 from top to bottom. The two sets of reflux units 13 work together to make phosgene and HCl gas easier to separate. The working principle is as follows: first, the condensing elements 132 in the two sets of the reflux units 13 start the cooling operation at the same time. Then, after the temperature of the absorption tower 10 is reduced to a certain range, the spraying structure 14 starts spraying the solvent. Meanwhile, the mixed gas enters the absorption tower 10 through the feeding port 11. The temperature of the solvent rapidly drops when it reaches the condensing member 132. By utilizing the characteristic that HCl is not easily soluble in the solvent, a large amount of phosgene and a small amount of HCl are absorbed by the solvent after the mixed gas passes through the first condensing element 132, and then the mixed gas drops along with the solvent. When the remaining mixed gas passes through the second condensing element 132, since a small amount of phosgene and a large amount of HCl remain in the mixed gas at this time, the absorption effect of the solvent on HCl is the worst at this time, so that phosgene in the mixed gas is further absorbed and separated, and the separation effect is optimal. Finally, the remaining mixture of a large amount of HCl and a very small portion of phosgene is discharged through the collection opening 12, and the phosgene content in the mixture is very low and can be substantially ignored, so that this portion of the mixture can be collected for other purposes. Since the condensing member 132 is located between the recovery pan 133 and the distribution nozzle 131, the dropped solvent is recovered by the recovery pan 133 and then sprayed again through the distribution nozzle 131 to re-separate HCl gas contained in the solvent.

The recovery pan 133 serves to collect the phosgene-absorbed solvent falling from the condensing member 132. When the solvent level in the recovery tray 133 reaches a certain height, the solvent in the recovery tray 133 is conveyed to the distribution spray nozzle 131 through the return pipe 134, and the distribution spray nozzle 131 re-sprays the solvent, so that circulating jet flow is realized. The purpose of this design is to create turbulence in the solvent in the first recovery pan 133, which causes a portion of the HCl contained in the solvent to be released and separated, thereby further reducing the proportion of HCl contained in the solvent.

A micro pump 135 is disposed in the recovery pan 133, and the return pipe 134 is connected to the micro pump 135. When the liquid level in the recovery pan 133 reaches a certain height, the micro pump 135 is activated. The micro-pump 135 is responsible for sending the solvent from the recovery pan 133 to the distribution nozzle 131 through the return pipe 134. The solvent may be turbulent during the solvent extraction process by the micro-pump 135, and the solvent may collide with each other in layers, thereby releasing HCl gas.

In conclusion, the scheme has the following beneficial effects: firstly, abandoned more dangerous pressurization absorption mode among the prior art, chooseed the mode separation phosgene and HCl of fractional condensation for whole separation process potential safety hazard significantly reduces. Secondly, a large amount of phosgene is separated from the mixed gas under the action of the condensing part 132 and the solvent, and then the residual phosgene in the mixed gas is further absorbed under the action of the second group of reflux units 13 and the solvent, namely, the phosgene and the HCl are sufficiently separated by a fractional condensation absorption method, so that the proportion of impurities in the phosgene and the HCl is greatly reduced, and the phosgene is convenient to recycle and utilize. Thirdly, the ammonium salt substances generated when the separated phosgene reacts with the amine raw material in the scheme are greatly reduced, so that the problem that the reaction device is blocked by the ammonium salt substances is avoided.

In this embodiment, the solvent for absorbing phosgene can be selected from a variety of solvents, one of which is chlorobenzene.

To further separate phosgene from HCl, we can choose the following way:

a condensing assembly 15 is arranged between the spraying structure 14 and the collecting port 12, the condensing assembly 15 is an intensive tube type heat exchanger, and the intensive tube type heat exchanger comprises a plurality of closely-arranged heat exchange pipelines. The condensing assembly 15 is formed by closely arranging a plurality of heat exchange pipes, and a small gap is left between adjacent heat exchange pipes. The structure of the condensing assembly 15 is similar to a demister, when the mixed gas passes through a small gap between heat exchange pipes, the gas can pass through, small liquid drops of the solvent in the mixed gas can be condensed by the heat exchange pipes, and finally the small liquid drops can fall back to the bottom of the absorption tower kettle 10 after being gathered. The condensing assembly 15 thus functions both as a condensing and as a filtering function for the demister. This way, the mixed gas is prevented from bringing small liquid drops of the solvent out of the absorption tower kettle 10 through the collecting port 12, and further, the content of phosgene in HCl is reduced, so that HCl and phosgene in the mixed gas can be fully separated.

After separating phosgene from HCl, we also need to consider how to efficiently recover the phosgene absorbed by the solvent for subsequent use. In the traditional mode, the phosgene can be recovered only by the solvent through rectification and analysis, and the solvent through rectification and analysis contains polymerized leftover impurities, so that the frequency and the effect of repeated use of the solvent are influenced.

Therefore, a spraying analysis tower 30 is arranged on one side of the absorption tower kettle 10, the spraying analysis tower 30 is connected with the absorption tower kettle 10 through a discharge pipeline 27, a gas-liquid separator 31 and a liquid separation valve 32 are respectively arranged at the top and the bottom of the spraying analysis tower 30, a sprayer 33 is arranged between the liquid separation valve 32 and the gas-liquid separator 31, a preheater 34 is arranged between the sprayer 33 and the liquid separation valve 32, one end of the preheater 34 is connected with the liquid separation valve 32, and the other end of the preheater 34 is connected with the sprayer 33. The solvent absorbed with phosgene in the absorption tower kettle 10 is conveyed to a spray desorption tower 30 through a discharge port 26 and a discharge pipeline 27, and then the solvent reaches a preheater 34 through a liquid separation valve 32. The preheater 34 heats the portion of solvent to the phosgene bubble point temperature, and the portion of solvent is then transported to the sprayer 33, and the sprayer 33 sprays the portion of solvent to the spray stripper 30, where the solvent is separated from the phosgene. The phosgene rises slightly, the solvent falls back to the bottom of the spray analysis tower 30 heavily, the phosgene carries little solvent mist to the gas-liquid separator 31 along the spray analysis tower 30, and the gas-liquid separator 31 separates the phosgene from the solvent mist, so that pure phosgene is obtained, and the phosgene is recovered. In the process, the residual solvent can be continuously recycled.

In order to conveniently recycle the solvent, preferably, a condenser 35 is arranged between the liquid separation valve 32 and the spraying structure 14, one end of the condenser 35 is connected with the liquid separation valve 32, and the other end of the condenser 35 is connected with the spraying structure 14. In this embodiment, the liquid dividing valve 32 is connected to both the preheater 34 and the condenser 35, so as to divide the solvent in the spray resolution tower 30. The liquid separation valve 32 sends the solvent containing phosgene to the preheater 34 to realize the separation of phosgene and solvent; the liquid separating valve 32 sends the pure solvent to the condenser 35 to be cooled, and then the condenser 35 sends the cooled solvent to the spraying structure 14, so that the solvent is recycled.

In order to further avoid the recovery of phosgene carrying solvent mist, it is preferable that a demister 36 is provided between the sprayer 33 and the gas-liquid separator 31, and the demister 36 covers the sprayer 33. The purpose of the demister 36 is to separate liquid droplets entrained in the gas in the column to ensure mass transfer efficiency, reduce loss of valuable material and improve operation of the compressor after the column.

In order to increase the effect of the phosgene coming out of the solvent, it is preferable that the sprayer 33 includes a plurality of spray nozzles 37, and the plurality of spray nozzles 37 are located on a surface of the sprayer 33 facing the gas-liquid separator 31. The design ensures that the solvent containing phosgene stays in the air for a longer time, has a larger contact surface with the air, and can collide with the upstream liquid in the downstream process, thereby increasing the turbulent process and the precipitation effect.

In the resolving process, it is also necessary to ensure that phosgene is always at the bubble point temperature, and for this purpose, the spray resolving tower comprises a first tower body 38 and a second tower body 39, the second tower body 39 is located inside the first tower body 38, and an insulating layer 40 is filled between the second tower body 39 and the first tower body 38. The existence of the heat preservation layer 40 prevents the rapid temperature loss of the spray analysis tower 30, thereby reducing the energy waste. The heat-insulating layer in the scheme adopts heat-insulating materials, including but not limited to materials such as polyurethane foam, polyphenyl board, phenolic foam and the like.

In this scheme the condensing part 132 is the tubulose interchanger, the tubulose interchanger includes refrigerant import and refrigerant export, the refrigerant import is connected with the lateral wall of absorption tower cauldron 10, the refrigerant export is located one side that refrigerant import was kept away from to absorption tower cauldron 10. To assist the solvent in absorbing phosgene, the packing in the condensing member 132 is preferably a corrosion resistant stainless steel ring material, the purpose of which is to increase the phosgene absorbing area.

In conclusion, in order to conveniently separate phosgene and HCl, the absorption tower kettle 10 is introduced, and in order to effectively recover phosgene, the spray analysis tower 30 is introduced. The absorption tower kettle 10 enables HCl and phosgene to be fully separated in a fractional condensation mode through two sets of reflux units 13. In order to improve the separation effect, a condensing assembly 15 is additionally arranged in the absorption tower kettle 10. The condensation assembly 15 is used for condensing and filtering part of the mist solvent carried in the HCl, so that the HCl collected from the collection port 12 is purer. The mist solvent is condensed and gathered on the condensing component 15 and finally falls to the bottom of the absorption tower kettle 10, so that the waste of phosgene can be avoided. The solvent is pumped by the micro pump 135 so that the solvent has a turbulent effect, releasing the HCl absorbed in the solvent, reducing the HCl content of the recovered light. In order to separate the solvent and the phosgene conveniently, a sprayer 33 is arranged in the spray analysis tower 30, the phosgene reaches the bubble point temperature after the solvent entering the spray analysis tower 30 is preheated by a preheater 34, the phosgene is separated from the solvent after the solvent is sprayed by the sprayer 33, and the mist solvent carried by the phosgene is filtered after the phosgene passes through the gas-liquid separator 31, so that pure phosgene is obtained. In order to recycle the solvent, the liquid separation valve 32 is further connected to a condenser 35, and the solvent is cooled by the condenser 35. And may be returned to the spray structure 14. The scheme avoids a high-temperature high-pressure absorption analysis mode in a traditional mode, improves safety, reduces energy waste, enables HCl and phosgene to be fully separated, and avoids phosgene from reacting with amine substances to form ammonium salt to block a reaction device in use.

The present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes without creative labor from the above conception, and all the changes fall within the protection scope of the present invention.

Claims (9)

1. The utility model provides a phosgene recovery unit in isocyanate production process, includes the absorption tower cauldron, the top and the bottom of absorption tower cauldron are provided with respectively collects mouth and pay-off mouth, its characterized in that: the absorption tower kettle is characterized in that a backflow unit is arranged inside the absorption tower kettle, a spraying structure is arranged on the upper portion of the backflow unit, the backflow unit comprises a distribution sprayer, a condensation piece and a recovery disc which are sequentially arranged from top to bottom, and the distribution sprayer and the recovery disc are connected through a backflow pipe.

2. The apparatus for recovering phosgene in the process of producing isocyanate according to claim 1, wherein: the reflux units are divided into two groups, and the two groups of reflux units are sequentially distributed in the absorption tower kettle from top to bottom.

3. The apparatus for recovering phosgene in the process of producing isocyanate according to claim 1, wherein: a micro pump machine is arranged in the recovery disc, and the return pipe is connected with the micro pump machine.

4. The apparatus for recovering phosgene in isocyanate production according to claim 1, wherein: and a condensation component is arranged between the spraying structure and the collecting port and comprises a plurality of closely-arranged heat exchange pipelines.

5. The apparatus for recovering phosgene in the process of producing isocyanate according to claim 1, wherein: one side of absorption tower cauldron is provided with sprays the analytic tower, the top and the bottom of spraying the analytic tower are equipped with vapour and liquid separator and branch liquid valve respectively, be provided with the spray thrower between branch liquid valve and the vapour and liquid separator, be provided with the pre-heater between spray thrower and the branch liquid valve, the both ends of pre-heater are connected with branch liquid valve, spray thrower respectively.

6. The apparatus for recovering phosgene in isocyanate production according to claim 5, wherein: a condenser is arranged between the liquid distribution valve and the sprayer, and two ends of the condenser are connected with the liquid distribution valve and the spraying structure respectively.

7. The apparatus for recovering phosgene in the process of producing isocyanate according to claim 5, wherein: a demister is arranged between the sprayer and the gas-liquid separator and covers the sprayer.

8. The apparatus for recovering phosgene in isocyanate production according to claim 7, wherein: the sprayer comprises a plurality of spraying heads spraying upwards.

9. The apparatus for recovering phosgene in the process of producing isocyanate according to claim 5, wherein: the spray analysis tower comprises a first tower body and a second tower body, the second tower body is located inside the first tower body, and a heat insulation layer is filled between the second tower body and the first tower body.

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