CN115121083B - Device and method for purifying and separating ammonia-containing tail gas in carbonylation intermediate production process - Google Patents

Abstract

The invention provides a device and a method for purifying and separating ammonia-containing tail gas in the production process of a carbonylation intermediate, wherein the device sequentially comprises a gas-liquid separation unit, an ammonium bicarbonate capturing unit, a compression separation unit and an ammonia separation unit, the gas-liquid separation unit comprises a condenser and a first gas-liquid separator, the ammonium bicarbonate capturing unit comprises an ammonium bicarbonate capturing device, the compression separation unit comprises a compressor and a second gas-liquid separator, the ammonia separation unit comprises an ammonia separation tower and a third gas-liquid separator, and liquid phase outlets of the first, second and third gas-liquid separators are connected to the same pipeline for recycling. According to the invention, through the arrangement of the ammonium bicarbonate trapping unit and the multi-stage separation unit, most of organic components are separated through the gas-liquid separation unit, ammonium bicarbonate is separated out through the ammonium bicarbonate trapping unit, and organic matters are separated through the modes of compression separation and tower separation, so that the purification of ammonia-containing tail gas and the efficient recovery of ammonia, ammonium bicarbonate and organic components are realized, meanwhile, the problem that a pipeline is easy to block can be effectively solved, and the continuous and stable operation can be realized for a long time.

Description

A device and method for purifying and separating ammonia-containing tail gas in the production process of carbonylation intermediates

Technical field

The invention belongs to the technical field of organic synthesis and separation, and relates to a device and method for purifying and separating ammonia-containing tail gas in the production process of carbonylation intermediates.

Background technique

As a common product in the chemical industry, urea can be used to prepare important chemicals such as carbamates, carbonates, and diphenyl ureas. Since urea contains a carbonyl group in its structure, it is generally used in oxo synthesis reactions. During the reaction, urea often Small molecules of ammonia will be released, and the ammonia-containing tail gas generated needs to be separated and recycled. However, due to the characteristics of urea such as easy moisture absorption and poor thermal stability, ammonia will also entrain ammonium bicarbonate, and ammonium bicarbonate will crystallize when it is cold, which is easy to Block the exhaust pipeline and affect the continuous production of the device.

At present, industrial methods for processing and recycling ammonia-containing tail gas mainly include water absorption method and compression separation method to obtain ammonia water and liquid ammonia respectively. Among them, the water absorption method usually uses the method of heating the tail gas and then spraying water with it, which can avoid the spray process. Medium carbon ammonium blocks the pipeline, but this process consumes a lot of water, and when the ammonia-containing gas phase contains organic solvents, it will cause problems such as unqualified ammonia or substandard tail gas emission pollutants; the compression separation method usually liquefies ammonia to form a liquid Ammonia, however, the compressor inlet temperature requirement in this method is low, and the problem of ammonium bicarbonate blocking the pipeline is prone to occur, and the energy consumption of this method is high.

For the application of urea in organic synthesis, for example, the non-phosgene method is used to produce isocyanate, specifically using steps such as urea carbonylation, alcoholysis, condensation and pyrolysis. Among them, N,N-diphenylurea (DPU) is used in this method. An important intermediate is the product of urea carbonylation. This process will produce a large amount of ammonia gas, entraining solvents and ammonium bicarbonate. The effective components in the ammonia-containing tail gas must be separated and recovered, which has an important impact on the stable production of this product. .

CN 102001970A discloses a method for preparing diphenyl urea by direct reaction of urea and aniline through nitrogen stripping. In this method, urea and aniline are added into a reaction kettle at a certain molar ratio, stirred, nitrogen gas is passed through to extract the reaction by-product ammonia, and heated The temperature is raised to a reaction temperature of 145 to 180°C, and the reaction is carried out under normal pressure. The nitrogen is passed through the reaction for 2 to 6 hours. After the reaction is completed, the stirring is stopped to allow natural cooling and crystallization. The reaction crystallized product is suction-filtered to obtain a crystalline diphenyl urea product; The method mainly involves the control of the preparation process of diphenyl urea, and does not explicitly mention the subsequent treatment and recovery of ammonia-containing gas.

CN 110817900A discloses a device and method for separating ammonia gas containing carbon dioxide and organic matter. The device includes a primary scrubber, a primary scrubber cooler, a secondary scrubber, a secondary scrubber cooler, a compressor, a gas Liquid separation tank, ammonia refining tower and its top condenser, reflux tank and reboiler, heat exchanger, organic separation tower and its top condenser, reflux tank and reboiler, carbonization kettle, filter; that is, through First-level washing, second-level washing, pressurization, ammonia refining, organic matter separation, carbonization and filtration steps are required to obtain liquid ammonia products and ammonium carbonate products; the structure of the device is relatively complex, there are many operating steps, and it is not clear that the compression process may produce The treatment of ammonium bicarbonate, and the operation process is greatly affected by organic components.

To sum up, in the process of producing carbonylation intermediates by non-phosgene method, for the treatment of ammonia-containing tail gas, it is necessary to select appropriate equipment and operations according to the composition of the tail gas, so that it can achieve high efficiency of ammonia and organic components. Recycling can also avoid the problem of pipeline blockage.

Contents of the invention

In view of the problems existing in the prior art, the purpose of the present invention is to provide a device and method for the purification and separation of ammonia-containing tail gas in the production process of carbonylation intermediates. The device is configured with an ammonium bicarbonate capture unit and a multi-stage separation unit. The ammonia-containing organic tail gas is first condensed and separated to separate most of the organic components, and then the ammonium bicarbonate is precipitated, and then the remaining organic components are removed through compression separation and tower separation to achieve the synthesis of ammonia and organic components in the tail gas from oxo intermediates. And the separation and recovery of ammonium bicarbonate, and can effectively solve the problem of easy blockage of pipelines.

To achieve this goal, the present invention adopts the following technical solutions:

On the one hand, the present invention provides a device for purifying and separating ammonia-containing tail gas in the production process of carbonylation intermediates. The device sequentially includes a gas-liquid separation unit, an ammonium bicarbonate capture unit, a compression separation unit and an ammonia separation unit. The gas-liquid separation unit includes a condenser and a first gas-liquid separator. The ammonium bicarbonate capture unit includes an ammonium bicarbonate trap. The compression separation unit includes a compressor and a second gas-liquid separator. The ammonia separation unit It includes an ammonia separation tower and a third gas-liquid separator, and the liquid phase outlets of the first gas-liquid separator, the second gas-liquid separator and the third gas-liquid separator are connected to the same pipeline for recycling.

In the present invention, for the production process of carbonylation intermediates, especially the intermediates for the production of isocyanates, such as diphenyl urea, nitrogen-containing organic raw materials are usually used. After the carbonylation reaction, ammonia-containing tail gas is generated. Based on the characteristics of the raw materials, the tail gas It also contains ammonium bicarbonate and organic components, so the device of the present invention is provided with an ammonium bicarbonate capture unit and a multi-stage separation unit, wherein the ammonium bicarbonate capture unit is provided between the multi-stage separation units, that is, first through gas-liquid separation Unit, most of the organic components are condensed and separated, and then the ammonium bicarbonate is separated out through the structural design of the ammonium bicarbonate trap. The remaining ammonia-containing gas is further separated by compression separation and tower separation to further separate the organic matter. It effectively purifies the synthesis tail gas of carbonylation intermediates and efficiently recovers ammonia, ammonium bicarbonate and organic components, and at the same time solves the problem that ammonium bicarbonate easily causes pipeline blockage; the device has a simple structure, can operate continuously and stably for a long time, and has low cost. Low, high production efficiency.

The following are preferred technical solutions of the present invention, but are not limited to the technical solutions provided by the present invention. Through the following technical solutions, the technical objectives and beneficial effects of the present invention can be better achieved and realized.

As a preferred technical solution of the present invention, the ammonia-containing tail gas comes from a carbonylation intermediate synthesis unit, preferably an N,N-diphenyl urea synthesis unit.

Preferably, the condenser includes a first condenser and a second condenser, the gas phase outlet of the first condenser is connected to the second condenser, and the liquid phase outlet of the first condenser is connected to the carbonylation intermediate. Synthetic unit.

Preferably, the first condenser is a vertical condenser, the second condenser is a horizontal condenser, both are shell-and-tube heat exchangers, and the ammonia-containing gas passes through the tube side.

In the present invention, the first condenser and the second condenser are used to cool ammonia-containing gases in different temperature ranges, so different heat exchange media can be selected. For example, heat transfer oil can be selected for the first condenser, and circulation can be selected for the second condenser. water.

Preferably, the first gas-liquid separator is a vertical tank, the top outlet of the first gas-liquid separator is connected to the inlet of the ammonium bicarbonate trap, and the bottom liquid phase outlet of the first gas-liquid separator is Connected to the carbonylation intermediate synthesis unit.

In the present invention, the top gas phase pipeline of the first gas-liquid separator can be provided with heat tracing, for example, low-pressure steam is selected to avoid early precipitation of ammonium bicarbonate in the pipeline due to temperature reduction.

As a preferred technical solution of the present invention, the ammonium bicarbonate trap is a vertical heat exchanger with a U-shaped tube inside as the tube side. The heat exchange medium passes through the tube side. The inlet and outlet of the heat exchange medium are both located at The top of the ammonium bicarbonate trap.

Preferably, the middle part of the ammonium bicarbonate trap is provided with a partition plate along the longitudinal direction, and the partition plate extends to the bottom of the U-shaped tube.

Preferably, an ammonia-containing gas inlet and an ammonia-containing gas outlet are respectively provided on the upper sides of the ammonium bicarbonate trap on both sides of the partition.

Preferably, a baffle is provided in the shell of the ammonium bicarbonate trap, and the baffle is arranged horizontally or inclined downward.

In the present invention, a horizontal or slightly inclined downward baffle is provided in the shell of the ammonium bicarbonate trap, which is beneficial to the full contact and heat exchange between the ammonia-containing gas and the U-shaped tube, and disturbs the crystallization.

Preferably, an interlayer is provided at the bottom of the upper head tube plate of the ammonium bicarbonate trap, a spray heat medium inlet is provided on the side of the interlayer, and a spray port is provided at the bottom of the interlayer.

In the present invention, the bottom of the ammonium bicarbonate trap is provided with a discharge port for discharging the cleaning liquid after spray flushing, and a liquid level port is also provided on the lower side of the ammonium bicarbonate trap to control the cleaning liquid. of liquid level.

Preferably, the number of the ammonium bicarbonate traps is at least one, such as one, two, three or four. When there are more than two ammonium bicarbonate traps, they are arranged in parallel and run alternately.

In the present invention, the ammonium bicarbonate trap is used to capture ammonium bicarbonate during operation. After the operation is completed, the device is cut out to clean ammonium bicarbonate. The heat medium for cleaning ammonium bicarbonate can be steam or hot water, which is evenly sprayed on the U-shaped exchanger. On the heat pipe, the cleaning residual liquid is discharged from the boundary area for sewage treatment and ammonium bicarbonate recovery.

As a preferred technical solution of the present invention, the compressor includes a screw compressor.

Preferably, the compression separation unit further includes a cooler, which is disposed between the compressor and the second gas-liquid separator.

Preferably, both the cooler and the second gas-liquid separator are vertical tanks, and the compressed ammonia-containing gas passes through the shell side of the cooler.

Preferably, the liquid phase outlet of the second gas-liquid separator is connected to the carbonylation intermediate synthesis unit.

As a preferred technical solution of the present invention, the ammonia separation tower includes a packed tower, and the packing includes Pall rings and/or wire mesh corrugated packing.

Preferably, the top outlet of the ammonia separation tower is also connected to a top condenser, and the bottom outlet is also connected to a tower reboiler, both of which are vertical heat exchangers.

Preferably, the overhead condenser obtains a liquid ammonia product, and the liquid ammonia product enters the liquid ammonia storage tank.

Preferably, the third gas-liquid separator is a vertical tank, the top outlet of the third gas-liquid separator is connected to the lower inlet of the ammonia separation tower, and the bottom liquid phase outlet of the third gas-liquid separator is connected to the lower inlet of the ammonia separation tower. The carbonylation intermediate synthesis units are connected.

Preferably, a circulation pump is provided on the converging pipeline connecting the first gas-liquid separator, the second gas-liquid separator and the third gas-liquid separator to the carbonylation intermediate synthesis unit.

On the other hand, the present invention provides a method for purifying and separating ammonia-containing tail gas in the production process of carbonylation intermediates using the above device, and the method includes the following steps:

(1) Condensate the ammonia-containing tail gas and separate the gas and liquid to obtain a primary separation of ammonia-containing tail gas and liquid phase organic matter;

(2) Carry out ammonium bicarbonate capture on the primary separation ammonia-containing tail gas obtained in step (1) to obtain a secondary separation ammonia-containing tail gas and ammonium bicarbonate product, and the ammonium bicarbonate product is removed by thermal spray;

(3) Compress and gas-liquid separate the secondary separated ammonia-containing tail gas obtained in step (2) to obtain the third separation of ammonia-containing tail gas and liquid phase organic matter;

(4) The three times separated ammonia-containing tail gas obtained in step (3) is subjected to packing separation and gas-liquid separation to obtain purified gas and liquid phase organic matter. The purified gas is cooled to obtain a liquid ammonia product.

As a preferred technical solution of the present invention, the source of the ammonia-containing tail gas in step (1) includes the production process of carbonylation intermediates, preferably the process of producing N,N-diphenyl urea using urea and aniline as raw materials.

Preferably, the composition of the ammonia-containing tail gas in step (1) includes ammonia gas, ammonium bicarbonate, aniline, carbon dioxide and N-methylaniline.

Preferably, the temperature of the ammonia-containing tail gas in step (1) is 200-240°C, such as 200°C, 205°C, 210°C, 215°C, 220°C, 225°C, 230°C, 235°C or 240°C, etc., but It is not limited to the listed values, and other unlisted values within the range of values are also applicable.

Preferably, the condensation in step (1) includes primary condensation and secondary condensation.

Preferably, the temperature of the ammonia-containing tail gas after the primary condensation is lowered to 100-140°C, such as 100°C, 110°C, 120°C, 130°C or 140°C, etc., and the condensed liquid phase organic matter is returned to the production of oxonation intermediates process.

Preferably, after the secondary condensation, the temperature of the ammonia-containing tail gas drops to 60-80°C, such as 60°C, 65°C, 70°C, 75°C or 80°C, etc., and the liquid phase organic matter continues to condense and returns after gas-liquid separation. Production process of carbonylation intermediates.

Preferably, after the condensation and gas-liquid separation in step (1), the separated liquid phase organic matter accounts for 90 to 95% of the total liquid phase organic matter, such as 90%, 91%, 92%, 93%, 94% or 95%. %, etc., but are not limited to the listed values, and other unlisted values within this numerical range are also applicable.

In the present invention, since the condensation process includes primary condensation and secondary condensation, the liquid phase organic matter obtained after primary condensation accounts for 80 to 90% of the total liquid phase organic matter, such as 80%, 82%, 85%, 88% Or 90%, etc., and after secondary condensation and gas-liquid separation, part of it is liquefied again. The liquid phase organic matter separated after two condensations accounts for 90 to 95% of the total organic matter.

As a preferred technical solution of the present invention, the ammonium bicarbonate capture in step (2) is carried out in an ammonium bicarbonate trap.

Preferably, when ammonium bicarbonate is captured, the ammonia-containing tail gas after primary separation continues to cool to below 40°C, such as 40°C, 38°C, 35°C, 32°C, 30°C or 25°C, etc., and ammonium bicarbonate is precipitated out of the ammonium bicarbonate trap. on the U-shaped tube inside the collector.

Preferably, when the number of ammonium bicarbonate traps includes more than two, they run alternately.

Preferably, the thermal spray in step (2) uses a thermal medium to perform spray flushing to dissolve and remove the precipitated ammonium bicarbonate.

Preferably, the heat medium includes steam or hot water, and the removal time does not exceed 0.5h, such as 0.5h, 0.45h, 0.4h, 0.35h, 0.3h, 0.25h or 0.2h, etc., but is not limited to those listed value, other unlisted values within this value range are also applicable.

In the present invention, a heat medium spray is installed on the top of the ammonium bicarbonate trap. The heat medium is hot water or low-pressure steam, such as 80°C hot water or 0.2MPaG steam. Ammonium bicarbonate has a low melting point and is easily soluble in water. It can be cut out in the equipment. The system stage quickly decarbonizes ammonium and requires a short time.

As a preferred technical solution of the present invention, the pressure of the secondary separation of ammonia-containing tail gas in step (3) is 0.05 to 0.2MPaG, such as 0.05MPaG, 0.08MPaG, 0.1MPaG, 0.12MPaG, 0.15MPaG, 0.18MPaG or 0.2MPaG, etc. , but not limited to the listed values, other unlisted values within this range are also applicable.

Preferably, the temperature of the ammonia-containing tail gas is increased after the secondary separation after compression, and the gas-liquid separation is performed again after cooling.

Preferably, after the gas-liquid separation in step (3), the liquid phase organic matter is returned to the production process of carbonylation intermediates.

Preferably, the pressure of the three separations of ammonia-containing tail gas after the gas-liquid separation in step (3) is 2.6 to 3.2MPaG, such as 2.6MPaG, 2.7MPaG, 2.8MPaG, 2.9MPaG, 3.0MPaG, 3.1MPaG or 3.2MPaG, etc., but It is not limited to the listed values, and other unlisted values within the range of values are also applicable.

As a preferred technical solution of the present invention, the packing separation in step (4) is performed in an ammonia separation tower.

Preferably, the packing in the ammonia separation tower includes Pall ring and/or wire mesh corrugated packing.

Preferably, the pressure for packing separation in step (4) is 2.6-3.2MPaG, such as 2.6MPaG, 2.7MPaG, 2.8MPaG, 2.9MPaG, 3.0MPaG, 3.1MPaG or 3.2MPaG, etc., and the temperature is 60-70°C, such as 60°C, 62°C, 64°C, 66°C, 68°C or 70°C, etc., but are not limited to the listed values, and other unlisted values within the respective numerical ranges are also applicable.

Preferably, when the packing is separated in step (4), the ammonia-containing tail gas of the third separation is partially liquefied, the unliquefied gas phase leaves from the top of the tower, and the liquefied organic matter is heated in the tower kettle for gas-liquid separation again.

Preferably, the purified gas in step (4) is cooled to 40-60°C to obtain a liquid ammonia product, such as 40°C, 45°C, 50°C, 55°C or 60°C, etc., but is not limited to the listed values. The same applies to other values within the range not listed.

Preferably, after the gas-liquid separation in step (4), the gas phase is returned to the ammonia separation tower, and the liquid phase organic matter is returned to the production process of carbonylation intermediates.

Preferably, after the liquid phase organic matter separated in steps (3) and (4) is decompressed to 0 to 0.5MPaG, such as 0MPaG, 0.1MPaG, 0.2MPaG, 0.3MPaG, 0.4MPaG or 0.5MPaG, etc., it is combined with step (1) The separated liquid phase organic matter is mixed and transported to the carbonylation intermediate synthesis unit.

Compared with the prior art, the present invention has the following beneficial effects:

(1) The device of the present invention is configured with an ammonium bicarbonate capture unit and a multi-stage separation unit. It first passes through the gas-liquid separation unit to condense and separate most of the organic components, and then passes through the structural design of the ammonium bicarbonate trap. The ammonium bicarbonate is precipitated, and the remaining ammonia-containing gas is further separated from the organic matter through compression separation and tower separation, achieving the effective purification of the synthesis tail gas of the carbonylation intermediate and the efficient recovery of ammonia, ammonium bicarbonate and organic components. The ammonium bicarbonate removal rate reaches more than 99.5%, the organic component recovery rate reaches more than 99.9%, and the purity of the liquid ammonia product reaches more than 99.9%;

(2) The device of the present invention can effectively solve the problem of pipe blockage caused by ammonium bicarbonate, and can achieve continuous and stable operation of more than 3000 hours, with low equipment cost and high production efficiency.

Description of drawings

Figure 1 is a schematic structural diagram of a device for purifying and separating ammonia-containing tail gas in the production process of carbonylation intermediates provided in Embodiment 1 of the present invention;

Figure 2 is a schematic structural diagram of the ammonium bicarbonate trap provided in Embodiment 1 of the present invention;

Among them, 1-first condenser, 2-second condenser, 3-first gas-liquid separator, 4-ammonium carbonate trap, 41-U-shaped tube, 42-partition plate, 43-baffle plate, 44-interlayer, 45-spray port, 5-compressor, 6-cooler, 7-second gas-liquid separator, 8-ammonia separation tower, 9-third gas-liquid separator, 10-carbonylation intermediate Synthetic unit.

Detailed ways

In order to better explain the present invention and facilitate understanding of the technical solution of the present invention, the present invention will be described in further detail below. However, the following embodiments are only simple examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be determined by the claims.

The following are typical but non-limiting embodiments of the present invention:

Example 1:

This embodiment provides a device for purifying and separating ammonia-containing tail gas in the production process of carbonylation intermediates. The structural diagram of the device is shown in Figure 1, which sequentially includes a gas-liquid separation unit, an ammonium bicarbonate capture unit, and a compression separation unit. and an ammonia separation unit, the gas-liquid separation unit includes a condenser and a first gas-liquid separator 3, the ammonium bicarbonate capture unit includes an ammonium bicarbonate trap 4, the compression separation unit includes a compressor 5 and a second Gas-liquid separator 7. The ammonia separation unit includes an ammonia separation tower 8 and a third gas-liquid separator 9. The first gas-liquid separator 3, the second gas-liquid separator 7 and the third gas-liquid separator 9 The liquid phase outlet is connected to the same pipeline for reuse.

The ammonia-containing tail gas comes from the carbonylation intermediate synthesis unit 10, specifically the N,N-diphenyl urea synthesis unit.

The condenser includes a first condenser 1 and a second condenser 2. The gas phase outlet of the first condenser 1 is connected to the second condenser 2. The liquid phase outlet of the first condenser 1 is connected to the carbonylation outlet. Intermediate synthesis unit 10.

The first condenser 1 is a vertical condenser, and the second condenser 2 is a horizontal condenser. Both are shell-and-tube heat exchangers, and the ammonia-containing gas goes through the tube side.

The first gas-liquid separator 3 is a vertical tank. The top outlet of the first gas-liquid separator 3 is connected to the inlet of the ammonium bicarbonate trap 4. The bottom liquid phase of the first gas-liquid separator 3 is The outlet is connected to the carbonylation intermediate synthesis unit 10.

The structural schematic diagram of the ammonium bicarbonate trap 4 is shown in Figure 2. The ammonium bicarbonate trap 4 is a vertical heat exchanger with a U-shaped tube 41 inside as a tube side, and the heat exchange medium passes through the tube side. The inlet and outlet of the heat exchange medium are both arranged on the top of the ammonium bicarbonate trap 4.

The middle part of the ammonium bicarbonate trap 4 is provided with a partition 42 along the longitudinal direction, and the partition 42 extends to the bottom of the U-shaped pipe 41; the upper parts of the ammonium bicarbonate trap 4 on both sides of the partition 42 are respectively provided with Ammonia-containing gas inlet and ammonia-containing gas outlet.

A baffle 43 is provided in the shell of the ammonium bicarbonate collector 4, and the baffle 43 is arranged horizontally.

The bottom of the upper head tube plate of the ammonium bicarbonate collector 4 is provided with an interlayer 44, the side of the interlayer 44 is provided with a spray heat medium inlet, and the bottom of the interlayer 44 is provided with a spray port 45; the heat Medium steam.

The number of the ammonium bicarbonate traps 4 is two, and they are arranged in parallel and run alternately.

The compressor 4 is a screw compressor.

The compression separation unit also includes a cooler 6 , which is disposed between the compressor 5 and the second gas-liquid separator 7 .

The cooler 6 and the second gas-liquid separator 7 are both vertical tanks, and the compressed ammonia-containing gas passes through the shell side of the cooler 6 .

The liquid phase outlet of the second gas-liquid separator 7 is connected to the carbonylation intermediate synthesis unit 10 .

The ammonia separation tower 8 includes a packed tower, and the packing includes Pall rings.

The top outlet of the ammonia separation tower 8 is also connected to a tower top condenser, and the bottom outlet is also connected to a tower reboiler, both of which are vertical heat exchangers; the top condenser obtains liquid ammonia product, so The liquid ammonia product enters the liquid ammonia storage tank.

The third gas-liquid separator 9 is a vertical tank. The top outlet of the third gas-liquid separator 9 is connected to the lower inlet of the ammonia separation tower 8. The bottom liquid phase outlet of the third gas-liquid separator 9 is Connected to the carbonylation intermediate synthesis unit 10.

The first gas-liquid separator 3 , the second gas-liquid separator 7 and the third gas-liquid separator 9 are connected to the converging pipeline of the carbonylation intermediate synthesis unit 10 with a circulation pump.

Example 2:

This embodiment provides a device for purifying and separating ammonia-containing tail gas in the production process of carbonylation intermediates. The device sequentially includes a gas-liquid separation unit, an ammonium bicarbonate capture unit, a compression separation unit and an ammonia separation unit. The gas-liquid separation unit The separation unit includes a condenser and a first gas-liquid separator 3. The ammonium bicarbonate capture unit includes an ammonium bicarbonate trap 4. The compression separation unit includes a compressor 5 and a second gas-liquid separator 7. The separation unit includes an ammonia separation tower 8 and a third gas-liquid separator 9. The liquid phase outlets of the first gas-liquid separator 3, the second gas-liquid separator 7 and the third gas-liquid separator 9 are connected to the same pipe. Road recycling.

The ammonia-containing tail gas comes from the carbonylation intermediate synthesis unit 10, specifically the N,N-diphenyl urea synthesis unit.

The condenser includes a first condenser 1 and a second condenser 2. The gas phase outlet of the first condenser 1 is connected to the second condenser 2. The liquid phase outlet of the first condenser 1 is connected to the carbonylation outlet. Intermediate synthesis unit 10.

The first condenser 1 is a vertical condenser, and the second condenser 2 is a horizontal condenser. Both are shell-and-tube heat exchangers, and the ammonia-containing gas goes through the tube side.

The first gas-liquid separator 3 is a vertical tank. The top outlet of the first gas-liquid separator 3 is connected to the inlet of the ammonium bicarbonate trap 4. The bottom liquid phase of the first gas-liquid separator 3 is The outlet is connected to the carbonylation intermediate synthesis unit 10.

The ammonium bicarbonate trap 4 is a vertical heat exchanger with a U-shaped tube 41 inside as a tube side. The heat exchange medium passes through the tube side. The inlet and outlet of the heat exchange medium are both arranged in the ammonium bicarbonate trap. 4 on top.

The middle part of the ammonium bicarbonate trap 4 is provided with a partition 42 along the longitudinal direction, and the partition 42 extends to the bottom of the U-shaped pipe 41; the upper parts of the ammonium bicarbonate trap 4 on both sides of the partition 42 are respectively provided with Ammonia-containing gas inlet and ammonia-containing gas outlet.

A baffle 43 is provided in the shell of the ammonium bicarbonate collector 4, and the baffle 43 is inclined downward.

The bottom of the upper head tube plate of the ammonium bicarbonate collector 4 is provided with an interlayer 44, the side of the interlayer 44 is provided with a spray heat medium inlet, and the bottom of the interlayer 44 is provided with a spray port 45; the heat The medium is hot water.

The number of the ammonium bicarbonate traps 4 is three, which are arranged in parallel and run alternately.

The compressor 4 is a centrifugal compressor.

The compression separation unit also includes a cooler 6 , which is disposed between the compressor 5 and the second gas-liquid separator 7 .

The cooler 6 and the second gas-liquid separator 7 are both vertical tanks, and the compressed ammonia-containing gas passes through the shell side of the cooler 6 .

The liquid phase outlet of the second gas-liquid separator 7 is connected to the carbonylation intermediate synthesis unit 10 .

The ammonia separation tower 8 includes a packed tower, and the packing includes wire mesh corrugated packing.

The top outlet of the ammonia separation tower 8 is also connected to a tower top condenser, and the bottom outlet is also connected to a tower reboiler, both of which are vertical heat exchangers; the top condenser obtains liquid ammonia product, so The liquid ammonia product enters the liquid ammonia storage tank.

The third gas-liquid separator 9 is a vertical tank. The top outlet of the third gas-liquid separator 9 is connected to the lower inlet of the ammonia separation tower 8. The bottom liquid phase outlet of the third gas-liquid separator 9 is Connected to the carbonylation intermediate synthesis unit 10.

Example 3:

This embodiment provides a method for purifying and separating ammonia-containing tail gas in the production process of carbonylation intermediates. The method is carried out using the device in Example 1 and includes the following steps:

(1) The ammonia-containing tail gas is condensed and then separated into gas and liquid. The source of the ammonia-containing tail gas is the process of producing N,N-diphenylurea using urea and aniline as raw materials. The composition of the ammonia-containing tail gas includes 30wt% Ammonia gas, 67wt% aniline, and ammonium bicarbonate with a content of 100g/ ^m3 . The temperature of the ammonia-containing tail gas is 235°C. The condensation includes primary condensation and secondary condensation. After the primary condensation, the temperature of the ammonia-containing tail gas drops to 120°C. After the second condensation, the temperature of the ammonia-containing tail gas dropped to 60°C. After gas-liquid separation, the condensed aniline accounted for 95% of the total aniline. It was returned to the N,N-diphenylurea production process and the primary separation content was obtained. Ammonia tail gas;

(2) The primary separated ammonia-containing tail gas obtained in step (1) enters the ammonium bicarbonate trap 4 for ammonium bicarbonate capture. The primary separation ammonia-containing tail gas continues to cool to 38°C, and ammonium bicarbonate is precipitated in the ammonium bicarbonate trap 4. on the U-shaped pipe 41, and obtain secondary separation of ammonia-containing tail gas; the ammonium bicarbonate product is sprayed and flushed with steam, and the precipitated ammonium bicarbonate is dissolved and removed, and the removal time is 0.4h;

(3) Compress the secondary separated ammonia-containing tail gas obtained in step (2). The pressure before compression is 0.1MPaG. After the compression, the temperature of the secondary separated ammonia-containing tail gas increases, and the gas-liquid separation is performed again after cooling. Obtain three separations of ammonia-containing tail gas and liquid phase aniline. The pressure of the three separations of ammonia-containing tail gas is 2.6MPaG. The aniline is decompressed to 0.3MPaG and then returned to the N,N-diphenyl urea production process;

(4) Use the ammonia separation tower 8 for packing separation of the three times separated ammonia-containing tail gas obtained in step (3). The packing in the ammonia separation tower 8 is a Pall ring. The pressure of the packing separation is 2.9MPaG and the temperature is 66°C, the ammonia-containing tail gas after three separations is partially liquefied, and the unliquefied gas phase leaves from the top of the tower. The purified gas obtained is cooled to 40°C to obtain liquid ammonia product. The liquefied aniline is heated in the tower kettle for gas-liquid separation again, and the gas phase returns to the ammonia separation tower. 8. The liquid phase aniline is decompressed to 0.3MPaG and then returned to the N,N-diphenyl urea production process.

In this embodiment, the device and method are used to purify and separate ammonia-containing tail gas. According to the ammonium bicarbonate content and the recovery amount of aniline in the remaining tail gas in step (2), the ammonium bicarbonate removal rate reaches 99.97%, and the aniline recovery rate reaches 99.92 %, the purity of the liquid ammonia product can reach 99.95%, and the continuous and stable operation time of the device reaches 3000h.

Example 4:

This embodiment provides a method for purifying and separating ammonia-containing tail gas in the production process of carbonylation intermediates. The method is carried out using the device in Example 1 and includes the following steps:

(1) The ammonia-containing tail gas is condensed and then separated into gas and liquid. The source of the ammonia-containing tail gas is the process of producing N,N-diphenylurea using urea and aniline as raw materials. The composition of the ammonia-containing tail gas includes 35wt% Ammonia gas, 60wt% aniline, and ammonium bicarbonate with a content of 80g/ ^m3 . The temperature of the ammonia-containing tail gas is 240°C. The condensation includes primary condensation and secondary condensation. After the primary condensation, the temperature of the ammonia-containing tail gas drops to 140°C. After the second condensation, the temperature of the ammonia-containing tail gas dropped to 80°C. After gas-liquid separation, the condensed aniline accounted for 90% of the total aniline. It was returned to the N,N-diphenylurea production process and the primary separation content was obtained. Ammonia tail gas;

(2) The primary separated ammonia-containing tail gas obtained in step (1) enters the ammonium bicarbonate trap 4 for ammonium bicarbonate capture. The primary separation ammonia-containing tail gas continues to cool to 40°C, and ammonium bicarbonate is precipitated in the ammonium bicarbonate trap 4. on the U-shaped pipe 41, and obtain a secondary separation of ammonia-containing tail gas; the ammonium bicarbonate product is sprayed and flushed with steam, and the precipitated ammonium bicarbonate is dissolved and removed, and the removal time is 0.5h;

(3) Compress the secondary separation ammonia-containing tail gas obtained in step (2). The pressure before compression is 0.05MPaG. After the compression, the temperature of the secondary separation ammonia-containing tail gas increases, and the gas-liquid separation is performed again after cooling. Obtain three separations of ammonia-containing tail gas and liquid phase aniline. The pressure of the three separations of ammonia-containing tail gas is 3.0MPaG. The aniline is decompressed to 0.5MPaG and then returned to the N,N-diphenylurea production process;

(4) Use the ammonia separation tower 8 for packing separation of the three times separated ammonia-containing tail gas obtained in step (3). The packing in the ammonia separation tower 8 is a Pall ring. The pressure of the packing separation is 3.0MPaG and the temperature is 70°C, the ammonia-containing tail gas after three separations is partially liquefied, and the unliquefied gas phase leaves from the top of the tower. The purified gas obtained is cooled to 50°C to obtain liquid ammonia product. The liquefied aniline is heated in the tower kettle for gas-liquid separation again, and the gas phase returns to the ammonia separation tower. 8. The liquid phase aniline is decompressed to 0.5MPaG and then returned to the N,N-diphenyl urea production process.

In this embodiment, the device and method are used to purify and separate ammonia-containing tail gas. According to the ammonium bicarbonate content and the recovery amount of aniline in the remaining tail gas in step (2), the ammonium bicarbonate removal rate reaches 99.92%, and the aniline recovery rate reaches 99.94 %, the purity of the liquid ammonia product can reach 99.93%, and the continuous and stable operation time of the device reaches 3100h.

Example 5:

This embodiment provides a method for purifying and separating ammonia-containing tail gas in the production process of carbonylation intermediates. The method is carried out using the device in Example 2 and includes the following steps:

(1) Separate the gas and liquid of the ammonia-containing tail gas after condensation. The source of the ammonia-containing tail gas is the process of producing N,N-diphenyl urea using urea and aniline as raw materials. The composition of the ammonia-containing tail gas includes 40wt% Ammonia gas, 57.5wt% aniline, and ammonium bicarbonate with a content of 90g/ ^m3 . The temperature of the ammonia-containing tail gas is 200°C. The condensation includes primary condensation and secondary condensation. After the primary condensation, the temperature of the ammonia-containing tail gas drops. to 100°C. After secondary condensation, the temperature of the ammonia-containing tail gas drops to 70°C. After gas-liquid separation, the condensed aniline accounts for 92% of the total aniline. It returns to the N,N-diphenylurea production process and obtains primary separation. Ammonia-containing exhaust gas;

(2) Enter the primary separation ammonia-containing tail gas obtained in step (1) into the ammonium bicarbonate trap 4 for ammonium bicarbonate capture. The primary separation ammonia-containing tail gas continues to cool to 35°C, and ammonium bicarbonate is precipitated in the ammonium bicarbonate trap 4. on the U-shaped pipe 41, and obtain a secondary separation of ammonia-containing tail gas; the ammonium bicarbonate product is sprayed and rinsed with 80°C hot water, and the precipitated ammonium bicarbonate is dissolved and removed, and the removal time is 0.3h;

(3) Compress the secondary separated ammonia-containing tail gas obtained in step (2). The pressure before compression is 0.2MPaG. After the compression, the temperature of the secondary separated ammonia-containing tail gas increases, and the gas-liquid separation is performed again after cooling. Obtain three separations of ammonia-containing tail gas and liquid phase aniline. The pressure of the three separations of ammonia-containing tail gas is 3.2MPaG. The aniline is decompressed to 0.1MPaG and then returned to the N,N-diphenylurea production process;

(4) Use the ammonia separation tower 8 for packing separation of the three times separated ammonia-containing tail gas obtained in step (3). The packing in the ammonia separation tower 8 is wire mesh corrugated packing. The pressure of the packing separation is 3.2MPaG and the temperature is 3.2MPaG. At 60°C, the ammonia-containing tail gas after three separations is partially liquefied, and the unliquefied gas phase leaves from the top of the tower. The purified gas obtained is cooled to 60°C to obtain liquid ammonia product. The liquefied aniline is heated in the tower kettle for gas-liquid separation again, and the gas phase returns to the ammonia separation. In Tower 8, the liquid phase aniline is decompressed to 0.1MPaG and then returned to the N,N-diphenyl urea production process.

In this embodiment, the device and method are used to purify and separate ammonia-containing tail gas. According to the ammonium bicarbonate content and the recovery amount of aniline in the remaining tail gas in step (2), the ammonium bicarbonate removal rate reaches 99.9%, and the aniline recovery rate reaches 99.91 %, the purity of the liquid ammonia product can reach 99.92%, and the continuous and stable operation time of the device reaches 3200h.

Comparative example 1:

This comparative example provides a device and method for purifying and separating ammonia-containing tail gas in the production process of carbonylation intermediates. The device is similar to the device in Example 1. The only difference is that the ammonium bicarbonate trap 4 is replaced with a conventional one. Shell and tube heat exchanger.

The method is referred to the method in Example 3, the only difference is that in step (2), a shell-and-tube heat exchanger is used to perform heat exchange and cooling to precipitate ammonium bicarbonate in the primary separation of ammonia-containing tail gas.

In this comparative example, since the ammonium bicarbonate trap is not set up, ammonium bicarbonate precipitates in the conventional heat exchanger, which easily causes accumulation and blockage inside the heat exchanger, and it is difficult to directly rinse. It needs to be paused every time it runs for a period of time, which cannot be carried out for a long time. It runs stably for a long time, and as time goes by, the heat exchange effect decreases, making it difficult to fully analyze ammonium bicarbonate and affecting the subsequent separation process.

Based on the above examples and comparative examples, it can be seen that the device of the present invention is configured with an ammonium bicarbonate capture unit and a multi-stage separation unit. It first passes through the gas-liquid separation unit to condense and separate most of the organic components, and then passes through the gas-liquid separation unit. The structural design of the ammonium bicarbonate trap precipitates ammonium bicarbonate, and the remaining ammonia-containing gas is further separated from the organic matter through compression separation and tower separation, achieving effective purification of the synthesis tail gas of oxonation intermediates and ammonia, ammonium bicarbonate And efficient recovery of organic components, the removal rate of ammonium bicarbonate reaches more than 99.5%, the recovery rate of organic components reaches more than 99.9%, and the purity of liquid ammonia products reaches more than 99.9%; the device can effectively solve the problem that ammonium bicarbonate is easy to cause pipelines To solve the problem of clogging, the continuous and stable operation can reach more than 3000 hours, the equipment cost is low and the production efficiency is high.

The present invention illustrates the detailed devices and methods of the present invention through the above embodiments, but the present invention is not limited to the above detailed devices and methods, that is, it does not mean that the present invention must rely on the above detailed devices and methods to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent replacement of the device of the present invention, addition of auxiliary devices, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims (41)

1. A device for purifying and separating ammonia-containing tail gas in the production process of carbonylation intermediates, characterized in that the device includes a gas-liquid separation unit, an ammonium bicarbonate capture unit, a compression separation unit and an ammonia separation unit in sequence; the gas-liquid separation unit The liquid separation unit includes a condenser and a first gas-liquid separator, the ammonium bicarbonate capture unit includes an ammonium bicarbonate trap, the compression separation unit includes a compressor and a second gas-liquid separator, the ammonia separation unit includes Ammonia separation tower and third gas-liquid separator, the liquid phase outlets of the first gas-liquid separator, second gas-liquid separator and third gas-liquid separator are connected to the same pipeline for reuse; The ammonium bicarbonate trap is a vertical heat exchanger, with a U-shaped tube inside as a tube side, and the heat exchange medium passes through the tube side; the ammonium bicarbonate trap is provided with a partition along the longitudinal direction in the middle, and the partition is The plate extends to the bottom of the U-shaped tube, and the upper sides of the ammonium bicarbonate trap on both sides of the partition plate are respectively provided with ammonia-containing gas inlets and ammonia-containing gas outlets; the shell of the ammonium bicarbonate trap is provided with baffles plate, the baffle is set horizontally or inclined downward; the bottom of the upper head tube plate of the ammonium bicarbonate collector is provided with an interlayer, and the side of the interlayer is provided with a spray heat medium inlet, and the bottom of the interlayer Equipped with spray outlet. 2. The device according to claim 1, characterized in that the ammonia-containing tail gas comes from the carbonylation intermediate synthesis unit. 3. The device according to claim 2, characterized in that the ammonia-containing tail gas comes from the N,N-diphenyl urea synthesis unit. 4. The device according to claim 2, wherein the condenser includes a first condenser and a second condenser, the gas phase outlet of the first condenser is connected to the second condenser, and the first condenser The liquid phase outlet of the condenser is connected to the carbonylation intermediate synthesis unit. 5. The device according to claim 4, wherein the first condenser is a vertical condenser, the second condenser is a horizontal condenser, and both are shell and tube heat exchangers, Ammonia-containing gas goes through the pipeline. 6. The device according to claim 2, wherein the first gas-liquid separator is a vertical tank, and the top outlet of the first gas-liquid separator is connected to the inlet of the ammonium bicarbonate trap, so The bottom liquid phase outlet of the first gas-liquid separator is connected to the carbonylation intermediate synthesis unit. 7. The device according to claim 1, characterized in that the number of the ammonium bicarbonate traps is at least one, and when there are more than two ammonium bicarbonate traps, they are arranged in parallel and run alternately. 8. The apparatus of claim 1, wherein the compressor comprises a screw compressor. 9. The device according to claim 1, wherein the compression separation unit further includes a cooler, the cooler is disposed between the compressor and the second gas-liquid separator. 10. The device according to claim 9, characterized in that both the cooler and the second gas-liquid separator are vertical tanks, and the compressed ammonia-containing gas passes through the shell side of the cooler. 11. The device according to claim 2, wherein the liquid phase outlet of the second gas-liquid separator is connected to a carbonylation intermediate synthesis unit. 12. The device according to claim 1, wherein the ammonia separation tower includes a packed tower, and the packing in the packed tower includes Pall rings and/or wire mesh corrugated packing. 13. The device according to claim 1, characterized in that the top outlet of the ammonia separation tower is also connected to a top condenser, and the bottom outlet is also connected to a tower reboiler, both of which are vertical heat exchangers. device. 14. The device according to claim 13, characterized in that the overhead condenser obtains a liquid ammonia product, and the liquid ammonia product enters the liquid ammonia storage tank. 15. The device according to claim 2, wherein the third gas-liquid separator is a vertical tank, the top outlet of the third gas-liquid separator is connected to the lower inlet of the ammonia separation tower, and the The bottom liquid phase outlet of the third gas-liquid separator is connected to the carbonylation intermediate synthesis unit. 16. The device according to claim 2, characterized in that, the first gas-liquid separator, the second gas-liquid separator and the third gas-liquid separator are connected to the merging pipeline of the carbonylation intermediate synthesis unit. There is a circulation pump. 17. A method for purifying and separating ammonia-containing tail gas in the production process of carbonylation intermediates using the device according to any one of claims 1 to 16, characterized in that the method includes the following steps: (1) Condensate the ammonia-containing tail gas and separate the gas and liquid to obtain a primary separation of ammonia-containing tail gas and liquid phase organic matter; (2) Carry out ammonium bicarbonate capture on the primary separation ammonia-containing tail gas obtained in step (1) to obtain a secondary separation ammonia-containing tail gas and ammonium bicarbonate product, and the ammonium bicarbonate product is removed by thermal spray; (3) Compress and gas-liquid separate the secondary separated ammonia-containing tail gas obtained in step (2) to obtain the third separation of ammonia-containing tail gas and liquid phase organic matter; (4) The three times separated ammonia-containing tail gas obtained in step (3) is subjected to packing separation and gas-liquid separation to obtain purified gas and liquid phase organic matter. The purified gas is cooled to obtain a liquid ammonia product. 18. The method according to claim 17, characterized in that the source of the ammonia-containing tail gas in step (1) includes a carbonylation intermediate production process. 19. The method according to claim 18, characterized in that the source of the ammonia-containing tail gas in step (1) is the process of producing N,N-diphenyl urea using urea and aniline as raw materials. 20. The method according to claim 17, wherein the composition of the ammonia-containing tail gas in step (1) includes ammonia, ammonium bicarbonate, aniline, carbon dioxide and N-methylaniline. 21. The method according to claim 17, characterized in that the temperature of the ammonia-containing tail gas in step (1) is 200-240°C. 22. The method of claim 17, wherein the condensation in step (1) includes primary condensation and secondary condensation. 23. The method according to claim 22, characterized in that after the primary condensation, the temperature of the ammonia-containing tail gas is lowered to 100-140°C, and the condensed liquid phase organic matter is returned to the production process of carbonylation intermediates. 24. The method according to claim 22, characterized in that after the secondary condensation, the temperature of the ammonia-containing tail gas drops to 60-80°C, the liquid phase organic matter continues to condense, and returns to the carbonylation intermediate after gas-liquid separation. production process. 25. The method according to claim 17, characterized in that, after the condensation and gas-liquid separation in step (1), the separated liquid phase organic matter accounts for 90 to 95% of the total liquid phase organic matter. 26. The method according to claim 17, characterized in that the ammonium bicarbonate capture in step (2) is carried out in an ammonium bicarbonate trap. 27. The method according to claim 26, characterized in that when the ammonium bicarbonate is captured, the ammonia-containing tail gas of the primary separation continues to be cooled to below 40°C, and the ammonium bicarbonate is precipitated on the U-shaped tube in the ammonium bicarbonate trap. . 28. The method according to claim 26, characterized in that when the number of ammonium bicarbonate traps includes more than two, they are operated alternately. 29. The method according to claim 17, characterized in that the thermal spray in step (2) uses a thermal medium to perform spray flushing to dissolve and remove the precipitated ammonium bicarbonate. 30. The method according to claim 29, wherein the heat medium includes steam or hot water, and the removal time does not exceed 0.5h. 31. The method according to claim 17, characterized in that the pressure of the secondary separation of ammonia-containing tail gas in step (3) is 0.05-0.2MPaG. 32. The method according to claim 17, characterized in that after the compression, the temperature of the ammonia-containing tail gas is increased for the second separation, and the gas-liquid separation is performed again after cooling. 33. The method according to claim 17, characterized in that, after the gas-liquid separation in step (3), the liquid phase organic matter is returned to the production process of carbonylation intermediates. 34. The method according to claim 17, characterized in that the pressure of the ammonia-containing tail gas separated three times after the gas-liquid separation in step (3) is 2.6 to 3.2 MPaG. 35. The method according to claim 17, characterized in that the packing separation in step (4) is carried out in an ammonia separation tower. 36. The method according to claim 35, characterized in that the packing in the ammonia separation tower includes Pall ring and/or wire mesh corrugated packing. 37. The method according to claim 17, characterized in that the pressure for packing separation in step (4) is 2.6-3.2MPaG, and the temperature is 60-70°C. 38. The method according to claim 17, characterized in that when the packing is separated in step (4), the ammonia-containing tail gas of the third separation is partially liquefied, the unliquefied gas phase leaves from the top of the tower, and the liquefied organic matter is heated in the tower kettle for gasification again. liquid separation. 39. The method according to claim 17, characterized in that the purified gas in step (4) is cooled to 40-60°C to obtain a liquid ammonia product. 40. The method according to claim 35, characterized in that, after the gas-liquid separation in step (4), the gas phase is returned to the ammonia separation tower, and the liquid phase organic matter is returned to the production process of carbonylation intermediates. 41. The method according to claim 17, characterized in that, after the liquid phase organic matter separated in steps (3) and step (4) is decompressed to 0-0.5MPaG, it is mixed with the liquid phase organic matter separated in step (1), Transported to the carbonylation intermediate synthesis unit.