CN111646890A - Process method for preparing acetic acid by methanol carbonylation with reactor and rectifying tower thermally coupled - Google Patents
Process method for preparing acetic acid by methanol carbonylation with reactor and rectifying tower thermally coupled Download PDFInfo
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- C07C51/10—Preparation of carboxylic acids or their salts, halides or anhydrides by reaction with carbon monoxide
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
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Abstract
The invention relates to a process method for preparing acetic acid by methanol carbonylation with a reactor thermally coupled with a rectifying tower, which comprises the following steps: introducing methanol and CO into a reactor to carry out carbonylation reaction, sending reaction liquid at the outlet of the reactor into a flash evaporator to carry out flash evaporation, separating to obtain a liquid-phase component and a gas-phase component, and returning the liquid-phase component to the reactor; the gas phase component enters a catalyst catcher, the caught catalyst returns to the bottom of the flash evaporator, and the gas phase enters a light component tower for separation to obtain a first tower top light component and a first tower kettle heavy component; sending the heavy components in the first tower kettle into a heavy component tower for separation to obtain an acetic acid product; and the reaction liquid in the reactor is coupled with the tower bottom material of the heavy component tower for heat exchange. Compared with the prior art, the invention has the advantages of energy conservation and emission reduction, high product purity, easy system control, stable operation and the like.
Description
Technical Field
The invention relates to a process method for producing acetic acid by methanol carbonylation, in particular to a process method for preparing acetic acid by methanol carbonylation with a reactor thermally coupled with a rectifying tower.
Background
Acetic acid is an important chemical raw material with wide application, and the prior methanol low-pressure carbonyl synthesis acetic acid process has obvious industrial advantages. In the prior art, the reaction for producing acetic acid by methanol carbonylation takes CO and methanol as raw materials, the product acetic acid as a solvent, a noble metal Ir-Ru or Rh as a main catalyst, and methyl acetate, methyl iodide, lithium iodide and water are added to form a homogeneous catalytic reaction system. The steps for producing acetic acid by carbonylation of methanol generally include feeding methanol and CO to a reaction vessel for contact with a homogeneous catalyst solution and feeding the resulting mixture after contact to a flash column. Separating the mixture into a gas phase component containing acetic acid and a liquid phase component containing the main catalyst by flash evaporation, wherein the gas phase component containing the acetic acid is sent into a light component rectifying tower to be rectified and separated to obtain an acetic acid product, and the liquid phase component containing the catalyst is circulated and returned to the reaction kettle. During the carbonylation of methanol and CO in a reaction vessel, 2260kJ of heat is generated for every 1 ton of acetic acid, and in order to ensure the normal carbonylation, the generated heat must be removed from the reaction vessel by heat exchange to prevent the reaction vessel from overheating.
Chinese patent CN104250209B discloses a production method for preparing acetic acid by methanol carbonylation. The method directly sends the liquid phase solution after flash evaporation into a heat exchanger, removes reaction heat through heat exchange, and controls the temperature of a reaction kettle to be constant, but in the patent technology, the temperature of the material after flash evaporation is reduced from 210 ℃ to 160 ℃ of 125-; and because the device does not collect and recycle the catalyst, the loss of the catalyst is caused, and the economic benefit is lower. Therefore, improvement on the prior art is needed, so that economic benefits of the process are improved from the aspects of energy recycling, catalyst recycling and the like, and requirements of energy conservation and emission reduction are met.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a process method for preparing acetic acid by methanol carbonylation with a reactor thermally coupled with a rectifying tower.
The purpose of the invention can be realized by the following technical scheme:
a process method for preparing acetic acid by methanol carbonylation with a reactor thermally coupled with a rectifying tower comprises the following steps: introducing methanol and CO into a reactor to carry out carbonylation reaction, sending reaction liquid at the outlet of the reactor into a flash evaporator to carry out flash evaporation, separating to obtain a liquid-phase component and a gas-phase component, and returning the liquid-phase component to the reactor; the gas-phase component is sent into a light component tower for separation to obtain a first tower top light component and a first tower kettle heavy component; sending the heavy components in the first tower kettle into a heavy component tower for separation to obtain an acetic acid product; and the reaction liquid in the reactor is coupled with the tower bottom material of the heavy component tower for heat exchange.
The coupling heat exchange mode has two kinds, the first is that the reaction liquid and the tower kettle material of heavy component tower directly exchange heat in the tower kettle reboiler of heavy component tower:
the reaction liquid in the reactor is divided into two materials by a first circulating pump, wherein one material is sent to a reboiler at the bottom of a heavy component tower and returns to the reactor after coupling heat exchange, and the other material enters an external circulating heat exchanger for cooling and returns to the reactor; the temperature of the reaction liquid is 180-class 220 ℃, and the temperature of the materials in the tower bottom of the heavy component tower is 130-class 165 ℃.
The second type is that the reaction solution generates heating steam firstly, the heating steam further provides heat for a reboiler of the heavy component tower, and condensate of the steam returns to the external circulation heat exchanger to generate steam, so that a cycle is formed:
reaction liquid in the reactor enters an external circulation heat exchanger through a first circulating pump to exchange heat with desalted water to generate heating steam, the reaction liquid at the outlet of the external circulation heat exchanger returns to the reactor, the heating steam at the outlet of the circulation heat exchanger is sent to a tower kettle reboiler of the heavy component tower to heat tower kettle materials of the heavy component tower, the steam enters the heavy component tower reboiler to be heated to form condensed water, the condensed water returns to the external circulation heat exchanger to continuously exchange heat with reaction heat, desalted water resources are recycled, and emission is reduced. The temperature of the reaction liquid is 180-220 ℃, the temperature of the heating steam is 160-200 ℃, and the temperature of the materials in the tower bottom of the heavy component tower is 130-165 ℃.
In the invention, the reaction liquid obtained from the carbonylation reaction is subjected to flash evaporation, the light component obtained by the flash evaporator is crude acetic acid, and the light component of the crude acetic acid is removed in a light component tower: noncondensable gas, water, methyl acetate, methyl iodide and methanol, wherein the material after light component removal enters a heavy component tower to remove heavy components, and qualified acetic acid products are collected from a side line close to the top of the tower.
The reboiler of the heavy component tower can be directly heated by reaction liquid or heated by steam generated by the reaction liquid, so that on one hand, reaction heat can be removed, the temperature in the reactor is ensured to be stable, and the stable reaction is improved and powerfully guaranteed; on the other hand, the reaction heat is effectively utilized, and the steam consumption is saved. By adopting the process, the simulation data is checked by using 40 ten thousand tons of production data, the operation cost is saved by 5-30t/h, and the circulating water consumption is saved by 300-500 t/h.
The gas phase component obtained by flash evaporation of the flash evaporator enters a catalyst catcher, the trapped catalyst returns to the bottom of the flash evaporator, and the gas phase enters a light component tower for separation.
A gas-phase component washing device and a defoaming device are arranged in the catalyst catcher; the gas-phase component washing device comprises an atomizer, and liquid-phase materials from the top of the light component tower are introduced into the atomizer; the defoaming device comprises a fiber web.
The catalyst catcher adopted by the invention enables the flashed acetic acid steam containing the catalyst to form large liquid drop particles through the gas-phase component washing device, and then removes the large liquid drop particles through the defoaming device, thereby greatly improving the recovery rate of the catalyst.
The gas-phase component washing device is preferably a spraying device, the spraying device can introduce a stream of dilute acetic acid at the top of the light component tower into the catalyst catcher and atomize the dilute acetic acid, the atomized dilute acetic acid liquid drops can be mixed with flash-evaporated acetic acid steam containing the catalyst, the liquid drops containing the catalyst are combined with the atomized acetic acid liquid drops after mixing and grow up to form the diameter of the liquid drops which can be easily removed by the demister device, and then the liquid drops are removed and recovered, so that the loss of the catalyst is reduced. The spraying device can be used alone, or can be further combined with a tray plate or a filler, and the catalyst is further removed by washing the flash evaporation gas phase through the tray plate or the filler. That is, the gas-phase component washing apparatus may be a separate spraying apparatus or tray plate or packing; or the gas-phase components after flash evaporation pass through a tray plate or a packing and spraying device in turn.
The defoaming device is preferably a fiber mesh in the invention, the fiber mesh can be a fiber bundle mesh or a fiber screen, for example, the fibers can be glass fibers, carbon fibers, plastic fibers or ceramic fibers, the fiber mesh can make droplets aggregate and converge by using the effects of droplet inertia, collision on the fibers, condensation, hooking (molecular tension) and the like, the fiber mesh can have a droplet removal rate of 99% above 3um and 98% below 3um, the droplet removal effect on the droplets is better than that of a common screen mesh defoamer in the prior art, large droplets are finally formed and returned to a catalyst system, and the loss of the catalyst is reduced. The fiber net defoaming device can be used independently, and can also be matched with the existing defoaming devices, such as a wire mesh demister or a blade type liquid demister, and the existing defoaming devices can remove liquid drops in a gas phase, wherein the wire mesh demister can remove 99.8% of liquid with the particle size of more than 10um, and the blade type liquid demister can remove 98% of liquid with the particle size of more than 10 um.
Preferably, the matching scheme of the catalyst catcher in the invention is as follows: fiber mesh, wire mesh demister or blade type liquid demister, spraying device, tray plate or filler; a fiber web, a tray plate or a filler; thirdly, a fiber mesh, a wire mesh demister or a blade type liquid demister and a spraying device; fiber net, spraying device, tray plate or filler; silk screen demister or blade type liquid demister, spraying device, tray plate or filler.
Because the acetic acid from the flash evaporator contains metal catalyst, the catalyst loss of the common device with a recovery section is 0.18g/t acetic acid, the invention adds a catalyst trapping device, the catalytic loss can be obviously reduced after the catalyst trapping device is used, and the catalyst consumption can be reduced to 0.03-0.1 g/t.
Acetic acid products are obtained by side mining at the middle part of the heavy component tower, and light components at the second tower top at the tower top return to the middle part of the light component tower.
The tray number of the heavy component tower is 60-100, the operation pressure in the tower is-0.05-0.2 MPaG, and the tower top temperature is 100-140 ℃; and the acetic acid product is extracted from the tower trays on the 2 nd to 8 th layers.
The number of trays of the light component tower is 50-80, the operating pressure in the tower is 0.05-0.2MPaG, the temperature at the top of the tower is 90-140 ℃, and the temperature at the bottom of the tower is 145-165 ℃.
Compared with the prior art that acetic acid is extracted from the top of the heavy component tower, the purity of the acetic acid product obtained by the method can reach the excellent product level, and the purity of the acetic acid is greatly improved. In the prior art, acetic acid is extracted from the top, in order to ensure the purity of the acetic acid, the materials in the bottom of the light component tower are ensured not to contain light components, otherwise, the light components are discharged from the top of the heavy component tower due to the low boiling point of the light components, so that the quality of the acetic acid is influenced, and the light component tower needs to be strictly controlled; in the invention, acetic acid is laterally extracted, and the light component at the top of the heavy component tower returns to the light component tower, so that an acetic acid product with higher purity can be easily obtained, the product quality is easier to control, and the purity is higher than that extracted at the top of the tower.
And the light components at the first tower top of the light component tower enter a condenser for condensation and then enter a reflux tank for gas-liquid separation, so that the obtained gas-phase component material enters an absorption tower, and part of the liquid-phase material returns to the reaction kettle through a second circulating pump.
The second circulating pump is a variable frequency pump, and the density of the working medium of the variable frequency pump is 1000-2000kg/m3。
Liquid phase components of a material discharged from the top of the light component tower after being condensed by a condenser are water, acetic acid, methyl iodide and methyl acetate, and the components need to be returned to the reactor; the existing process adopts a liquid-liquid separator, also called liquid-liquid phase separator, the liquid phase components are separated into two phases, the liquid phase heavy phase mainly contains methyl iodide, the density of the methyl iodide is 2000kg/m3Left and right; the liquid phase light phase is water, acetic acid and methyl acetate, and the material density is about 1000kg/m3Because the density difference of the two phases of liquid is large, two pumps are needed to be respectively adopted, namely a heavy phase pump and a light phase pump to respectively send out the liquid, because for the pumps, the selection needs to be carried out according to the density of the conveyed working medium; the variable frequency pump is adopted in the invention, so that the application range of the working medium of the pump is improved, and two-phase liquid-phase materials can be sent out by adopting one pump, so that a liquid-liquid separator is not required. The liquid-liquid separator has complex internal parts, inconvenient operation and difficult control, so the method of adopting the variable frequency pump greatly improves the stability of the system, reduces the number of the pumps from two sets to one set, and is beneficial to reducing the equipment investment and the maintenance cost.
The light component tower top equipment of the invention can also adopt the scheme of a liquid-liquid separator and two pumps in the prior art: and feeding the light component at the first tower top of the light component tower into a condenser and then into a liquid-liquid separator for separation to obtain a liquid phase heavy phase, a liquid phase light phase and a gas phase component, feeding part of the liquid phase heavy phase, the liquid phase light phase and the gas phase component back to the reactor by a third circulating pump and a fourth circulating pump respectively, and feeding the gas phase component into an absorption tower.
The working medium density of the third circulating pump is 1200-2200 kg/m3The working medium density of the fourth circulating pump is 800～1500kg/m3。
Compared with the prior art, the invention has the following advantages:
(1) the reactor and the heavy component rectifying tower are thermally coupled, so that the reaction heat is fully utilized, and the medium-pressure steam consumption and the cooling circulating water consumption are saved; the requirements of energy conservation and emission reduction are met;
(2) acetic acid is collected from the side of the heavy component tower, and the light component at the top of the tower returns to the light component tower, so that the purity of the acetic acid product is greatly improved, and the quality of the acetic acid product is easily embraced;
(3) for the light component tower, the layered heavy phase and light phase in the reflux tank at the top of the tower are jointly sent back to the reactor by using a variable frequency pump, so that a liquid-liquid phase separator which has complicated internals, inconvenient operation and difficult control is omitted, and the running stability of the system is improved.
(4) The catalyst catcher is added, the loss of the catalyst is reduced, and the production cost is reduced;
(5) the invention improves the economic benefit of the process system in the aspects of energy conservation, catalyst recovery, improvement of the quality of acetic acid products and the like.
Drawings
FIG. 1 is a process flow diagram of example 1 of the present invention;
FIG. 2 is a process flow diagram of example 2 of the present invention;
in the figure, 1 is a reactor, 2 is a flash evaporator, 3 is a light component tower, 4 is a heavy component tower, 5 is a first circulating pump, 6 is a second circulating pump, 7 is an external circulating heat exchanger, 8 is a main catalyst circulating pump, 9 is a first condenser, 10 is a second condenser, 11 is a third condenser, 12 is a gas-liquid separator, 13 is a reflux tank, 14 is a tower kettle reboiler, 15 is desalted water, and 16 is a catalyst catcher.
Detailed Description
The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that variations and modifications can be made by persons skilled in the art without departing from the spirit of the invention. All falling within the scope of the present invention.
Example 1
A process method for preparing acetic acid by methanol carbonylation with a reactor thermally coupled with a rectifying tower is disclosed, the process flow diagram of which is shown in figure 1, and the process method comprises the following steps:
(1) carbonylation reaction
Methanol and CO are introduced into the reactor 1 to carry out carbonylation reaction, and the catalyst can adopt various catalysts used for methanol carbonylation reaction in the prior art, such as at least one of rhodium, rhodium-containing compounds, iridium-containing compounds, ruthenium and ruthenium-containing compounds as main catalysts; the promoter may be one conventionally used in the art for methanol carbonylation reactions, and may be, for example, methyl iodide. The temperature of the reaction liquid in the reactor 1 was controlled to 200 degrees, the pressure was controlled to 2.6MpaG, and the molar ratio of methanol to CO was 1.3 (1: 1.3). The gas phase part at the top of the reactor 1 passes through a third condenser 11 and then enters a gas-liquid separator 12 for condensation, a liquid phase and non-condensable gas are separated in the gas-liquid separator 12, wherein the liquid phase returns to the reactor 1, and the non-condensable gas is sent to an absorption tower.
(2) Flash evaporation
And (3) feeding the reaction liquid in the reactor 1 into a flash evaporator 2 for flash evaporation, separating to obtain a liquid phase component and a gas phase component, and feeding the liquid phase component back to the bottom of the reactor 1 by a main catalyst circulating pump 8. The operating parameters of the flash column are as given in the prior art.
(3) Catalyst trapping
The gas phase components of the flash evaporator 2 enter a catalyst catcher for catalyst catching, and a gas phase component washing device and a defoaming device are arranged in the catalyst catcher 16; the flash evaporated acetic acid steam containing the catalyst forms large liquid drop particles through the gas phase component washing device, and the large liquid drop particles are further removed through the defoaming device, so that the recovery rate of the catalyst is greatly improved.
Specifically, the gas phase component washing device is formed by sequentially arranging a spraying device and a tray plate or a filler, and combining the spraying device and the tray plate or the filler; the defoaming device is formed by sequentially arranging a fiber mesh, a wire mesh demister or a blade type liquid demister and combining the fiber mesh, the wire mesh demister or the blade type liquid demister.
(4) Light component tower
The gas phase components of the flash evaporator 2 enter a light component tower 3 for separation, the light components are removed, and a first tower top light component is obtained at the tower top, wherein the light component comprises non-condensable gas, water, methyl acetate, methyl iodide and methanol; the heavy component in the first tower kettle is obtained from the tower kettle, and the composition of the heavy component comprises water, acetic acid and a small amount of byproduct propionic acid. The number of trays of the light component tower 3 is 50, the operating pressure in the tower is 0.05MPaG, the temperature at the top of the tower is 90 ℃, and the temperature at the bottom of the tower is 145 ℃; the reflux ratio of the column was 1.
The gas phase at the top of the light component tower is condensed by a first condenser 9 and then sent into a reflux tank 13, gas-liquid separation is carried out in a reflux pipe 13, the gas phase material is non-condensable gas and sent into an absorption tower, part of the liquid phase material reflows, and the other part of the liquid phase material is sent back into the reactor 1 by a second circulating pump 6; because the components in the liquid phase material are water, methyl acetate, methyl iodide and methanol, the components can carry out liquid-liquid phase separation, the liquid phase heavy phase mainly contains methyl iodide, and the density of the methyl iodide is 2000kg/m3Left and right; the liquid phase light phase is water, acetic acid and methyl acetate, and the material density is about 1000kg/m3Because the density difference between the two is large, the second circulating pump 6 in this embodiment needs to adopt a variable frequency pump, and the density of the working medium of the variable frequency pump is 1000-3。
(5) Heavy ends column
The heavy components in the first tower kettle are sent into a heavy component tower 4 to be separated, the heavy components are removed, the gas phase at the top of the heavy component tower 1 enters a second condenser 10 to be condensed, the liquid phase flows back to the heavy component tower 4, the liquid phase is extracted as the light components and returns to a light component tower 3, the heavy component tower 4 is provided with a side extraction pipeline, acetic acid products are obtained by side extraction at the middle part of the heavy component tower 4, and the heavy components are extracted by the tower kettle. The number of trays of the heavy component tower 4 is 82, the operating pressure in the tower is 0MPaG, the temperature of the top of the tower is 118 ℃, and the temperature of the bottom of the tower is 150 ℃; the acetic acid product can be extracted from the tower trays of the 2 nd to 8 th layers.
(6) Reactor and bottom thermal coupling of heavies column
The reaction liquid in the reactor 1 is divided into two materials by a first circulating pump 5, wherein one material enters the tube side of a tower kettle reboiler 14 of the heavy component tower 4, the tower kettle material of the heavy component tower 4 passes through the shell side of the tower kettle reboiler 14, the high-temperature reaction liquid provides heat for the tower kettle material of the heavy component tower 4, and the reaction liquid flowing out of the tower kettle reboiler 14 returns to the reactor 1; in order to maintain the stability of the reaction temperature in the reactor 1, the other part of the reaction liquid passing through the first circulating pump 5 enters the external circulating heat exchanger 6, and returns to the reactor 1 after being cooled.
The reboiler of the heavy component tower in this embodiment can be directly heated by the reaction liquid or heated by the steam generated by the reaction liquid, so that on one hand, the reaction heat can be removed, the temperature in the reactor is ensured to be stable, and the stable reaction is improved and the powerful guarantee is provided; on the other hand, the reaction heat is effectively utilized, and the steam consumption is saved. By adopting the process, the simulation data is checked by using 40 ten thousand tons of production data, the operation cost is saved by 5-30t/h, and the circulating water consumption is saved by 300-500 t/h; the process of the embodiment is subjected to economic accounting, the production cost of producing 40 ten thousand tons of acetic acid can be saved by 3680 yuan/h yuan, and the cost of each ton of acetic acid is saved by about 73.6 yuan (steam is 180 yuan/t, and circulating water is 0.2 yuan/t).
Example 2
A process method for preparing acetic acid by methanol carbonylation with a reactor thermally coupled with a rectifying tower is disclosed, the process flow diagram of which is shown in figure 1, and the process method comprises the following steps:
(1) carbonylation reaction
Methanol and CO are introduced into the reactor 1 to carry out carbonylation reaction, and the catalyst can adopt various catalysts used for methanol carbonylation reaction in the prior art, such as at least one of rhodium, rhodium-containing compounds, iridium-containing compounds, ruthenium and ruthenium-containing compounds as main catalysts; the promoter may be one conventionally used in the art for methanol carbonylation reactions, and may be, for example, methyl iodide. The temperature of the reaction liquid in the reactor 1 was controlled to 220 degrees, the pressure was controlled to 3MpaG, and the molar ratio of methanol to CO was 1: 1. The gas phase part at the top of the reactor 1 passes through a third condenser 11 and then enters a gas-liquid separator 12 for condensation, a liquid phase and non-condensable gas are separated in the gas-liquid separator 12, wherein the liquid phase returns to the reactor 1, and the non-condensable gas is sent to an absorption tower;
(2) flash evaporation
And (3) feeding the reaction liquid in the reactor 1 into a flash evaporator 2 for flash evaporation, separating to obtain a liquid phase component and a gas phase component, and feeding the liquid phase component back to the bottom of the reactor 1 by a main catalyst circulating pump 8. The operating parameters of the flash column are as given in the prior art.
(3) Catalyst trapping
The gas phase components of the flash evaporator 2 enter a catalyst catcher for catalyst catching, and a gas phase component washing device and a defoaming device are arranged in the catalyst catcher 16; the flash evaporated acetic acid steam containing the catalyst forms large liquid drop particles through the gas phase component washing device, and the large liquid drop particles are further removed through the defoaming device, so that the recovery rate of the catalyst is greatly improved.
Specifically, a fiber mesh, a wire mesh demister or a blade-type liquid demister, and a spraying device are sequentially provided in the catalyst catcher 16 from top to bottom.
(4) Light component tower
The gas phase components of the flash evaporator 2 enter a light component tower 3 for separation, the light components are removed, and a first tower top light component is obtained at the tower top, wherein the light component comprises non-condensable gas, water, methyl acetate, methyl iodide and methanol; the heavy component in the first tower kettle is obtained from the tower kettle, and the composition of the heavy component comprises water, acetic acid and a small amount of byproduct propionic acid. The number of trays of the light component column 3 was 80, the operating pressure in the column was 0.2MPaG, the overhead temperature was 140 ℃, the bottom temperature was 165 ℃, and the reflux ratio of the column was 0.5.
The gas phase at the top of the light component tower is condensed by a first condenser 9 and then sent into a reflux tank 13, gas-liquid separation is carried out in a reflux pipe 13, the gas phase material is non-condensable gas and sent into an absorption tower, part of the liquid phase material reflows, and the other part of the liquid phase material is sent back into the reactor 1 by a second circulating pump 6; because the components in the liquid phase material are water, methyl acetate, methyl iodide and methanol, the components can carry out liquid-liquid phase separation, the liquid phase heavy phase mainly contains methyl iodide, and the density of the methyl iodide is 2000kg/m3Left and right; the liquid phase light phase is water, acetic acid and methyl acetate, and the material density is about 1000kg/m3Because the density difference between the two is large, the second circulating pump 6 in this embodiment needs to adopt a variable frequency pump, and the density of the working medium of the variable frequency pump is 1000-3。
(5) Heavy ends column
The heavy components in the first tower kettle are sent into the heavy component tower 4 to be separated, the heavy components are removed, the gas phase at the top of the heavy component tower 1 enters a second condenser 10 to be condensed, the liquid phase flows back to the heavy component tower 4, the gas phase is extracted as the light components and returns to the light component tower 3, the heavy component tower 4 is provided with a side extraction pipeline, acetic acid products are obtained by side extraction at the middle part of the heavy component tower 4, and the heavy components are extracted by the tower kettle. The tray number of the heavy component tower 4 is 100, the operation pressure in the tower is 0.2MPaG, the tower top temperature is 156 ℃, and the tower kettle temperature is 165 ℃; the acetic acid product can be extracted from the tower trays of the 2 nd to 8 th layers.
(6) Reactor and bottom thermal coupling of heavies column
The materials in the reactor 1 pass through a first circulating pump 5 and then enter the shell pass of an external circulating heat exchanger 6, desalted water 15 is introduced into the external circulating heat exchanger 6, and the materials in the reactor 1 heat the desalted water 15 to generate heating steam at 200 ℃; the reaction liquid at the outlet of the external circulation heat exchanger 6 returns to the reactor 1, the heating steam at the outlet of the circulation heat exchanger is sent to a tower kettle reboiler 14 of the heavy component tower 4 to exchange heat with the tower kettle material of the heavy component tower, and the temperature of the tower kettle material of the heavy component tower 4 is 165 ℃. In order to maintain the temperature stability in the reactor 1, the reaction solution passing through the external circulation heat exchanger 6 can enter a cooler to cool the reaction solution to a suitable temperature, so that the temperature of the reaction solution in the reactor is maintained within a set range; the flow rate of desalted water can be increased, more low-pressure steam is generated, and the excessive low-pressure steam is sent to other places needing heating for utilization.
Example 3
The main process flow of this example is the same as that in example 1, except that the gas phase at the top of the light component column of this example is subjected to gas-liquid separation by using a liquid-liquid separator, and the operational parameters of the whole process flow are different, specifically:
(1) carbonylation reaction
Methanol and CO are introduced into the reactor 1 to carry out carbonylation reaction, and the catalyst can adopt various catalysts used for methanol carbonylation reaction in the prior art, such as at least one of rhodium, rhodium-containing compounds, iridium-containing compounds, ruthenium and ruthenium-containing compounds as main catalysts; the promoter may be one conventionally used in the art for methanol carbonylation reactions, and may be, for example, methyl iodide. The temperature of the reaction liquid in the reactor 1 was controlled to 180 degrees, the pressure was controlled to 2.6MpaG, and the molar ratio of methanol to CO was 1: 1. The gas phase part at the top of the reactor 1 passes through a third condenser 11 and then enters a gas-liquid separator 12 for condensation, a liquid phase and non-condensable gas are separated in the gas-liquid separator 12, wherein the liquid phase returns to the reactor 1, and the non-condensable gas is sent to an absorption tower;
(2) flash evaporation
And (3) feeding the reaction liquid in the reactor 1 into a flash evaporator 2 for flash evaporation, separating to obtain a liquid phase component and a gas phase component, and feeding the liquid phase component back to the bottom of the reactor 1 by a main catalyst circulating pump 8. The operating parameters of the flash column are as given in the prior art.
(3) Catalyst trapping
The gas phase components of the flash evaporator 2 enter a catalyst catcher for catalyst catching, and a gas phase component washing device and a defoaming device are arranged in the catalyst catcher 16; the flash evaporated acetic acid steam containing the catalyst forms large liquid drop particles through the gas phase component washing device, and the large liquid drop particles are further removed through the defoaming device, so that the recovery rate of the catalyst is greatly improved.
Specifically, a fiber net, a spraying device, a tray plate, or packing is provided in the catalyst catcher 16 in this order from top to bottom.
(4) Light component tower
The gas phase components of the flash evaporator 2 enter a light component tower 3 for separation, the light components are removed, and a first tower top light component is obtained at the tower top, wherein the light component comprises non-condensable gas, water, methyl acetate, methyl iodide and methanol; the heavy component in the first tower kettle is obtained from the tower kettle, and the composition of the heavy component comprises water, acetic acid and a small amount of byproduct propionic acid. The number of trays of the light component column 3 was 80, the operating pressure in the column was 0.2MPaG, the overhead temperature was 140 ℃, the bottom temperature was 165 ℃, and the reflux ratio of the column was 0.5.
The gas phase at the top of the light component tower is condensed by a first condenser 9 and then sent into a reflux tank 13, gas-liquid separation is carried out in a reflux pipe 13, the gas phase material is non-condensable gas and sent into an absorption tower, part of the liquid phase material reflows, and the other part of the liquid phase material is sent back into the reactor 1 by a second circulating pump 6; because the components in the liquid phase material are water, methyl acetate, methyl iodide and methanol, the components can carry out liquid-liquid phase separation, the liquid phase heavy phase mainly contains methyl iodide, and the density of the methyl iodide is 2000kg/m3Left and right; the liquid phase light phase is water, acetic acid and methyl acetate, and the material density is about 1000kg/m3Because the density difference between the two is large, the second circulating pump 6 in this embodiment needs to adopt a variable frequency pump, and the density of the working medium of the variable frequency pump is 1000-3。
(5) Heavy ends column
The heavy components in the first tower kettle are sent into the heavy component tower 4 to be separated, the heavy components are removed, the gas phase at the top of the heavy component tower 1 enters a second condenser 10 to be condensed, the liquid phase flows back to the heavy component tower 4, the gas phase is extracted as the light components and returns to the light component tower 3, the heavy component tower 4 is provided with a side extraction pipeline, acetic acid products are obtained by side extraction at the middle part of the heavy component tower 4, and the heavy components are extracted by the tower kettle. The number of trays of the heavy component tower 4 is 60, the operation pressure in the tower is-0.05 MPaG, the temperature at the top of the tower is 97 ℃, and the temperature at the bottom of the tower is 130 ℃; the acetic acid product can be extracted from the tower trays of the 2 nd to 8 th layers.
(6) Reactor and bottom thermal coupling of heavies column
The materials in the reactor 1 pass through a first circulating pump 5 and then enter the shell pass of an external circulating heat exchanger 6, desalted water 15 is introduced into the external circulating heat exchanger 6, and the materials in the reactor 1 heat the desalted water 15 to generate heating steam at 160 ℃; the reaction liquid at the outlet of the external circulation heat exchanger 6 returns to the reactor 1, the heating steam at the outlet of the circulation heat exchanger is sent to a tower kettle reboiler 14 of the heavy component tower 4 to exchange heat with the tower kettle material of the heavy component tower, and the temperature of the tower kettle material of the heavy component tower 4 is 130 ℃. In order to maintain the temperature stability in the reactor 1, the reaction solution passing through the external circulation heat exchanger 6 can enter a cooler to cool the reaction solution to a suitable temperature, so that the temperature of the reaction solution in the reactor is maintained within a set range; the flow rate of desalted water can be increased, more low-pressure steam is generated, and the excessive low-pressure steam is sent to other places needing heating for utilization.
The light components at the first tower top of the light component tower 3 enter a condenser and then enter a liquid-liquid separator for separation to obtain liquid phase heavy phase, liquid phase light phase and gas phase components, part of the liquid phase heavy phase and the liquid phase light phase are respectively sent back to the reactor 1 by a third circulating pump and a fourth circulating pump, the gas phase components enter an absorption tower, and the working medium density of a third circulating pump for conveying the liquid phase heavy phase is 2000kg/m3The working medium density of a fourth circulating pump for conveying the liquid phase and the light phase is 1000kg/m3。
The foregoing description of specific embodiments of the present invention has been presented. It is to be understood that the present invention is not limited to the specific embodiments described above, and that various changes and modifications may be made by one skilled in the art within the scope of the appended claims without departing from the spirit of the invention.
Claims (10)
1. A process method for preparing acetic acid by methanol carbonylation with a reactor thermally coupled with a rectifying tower comprises the following steps: introducing methanol and CO into a reactor (1) to carry out carbonylation reaction, sending reaction liquid at an outlet of the reactor (1) into a flash evaporator (2) to carry out flash evaporation, separating to obtain a liquid-phase component and a gas-phase component, and returning the liquid-phase component to the reactor (1); the gas phase component is sent into a light component tower (3) for separation to obtain a first tower top light component and a first tower kettle heavy component; sending the heavy components in the first tower kettle into a heavy component tower (4) for separation to obtain an acetic acid product;
it is characterized in that the preparation method is characterized in that,
and the reaction liquid in the reactor (1) and the tower kettle material of the heavy component tower (4) are subjected to coupling heat exchange.
2. The process method for preparing acetic acid by methanol carbonylation with the reactor thermally coupled with the rectifying tower according to claim 1, wherein the reaction liquid in the reactor (1) is divided into two materials by a first circulating pump (5), wherein one material is sent to a kettle reboiler (14) of the heavy component tower (4) for coupled heat exchange and then returned to the reactor (1), and the other material is sent to an external circulation heat exchanger (6) for cooling and then returned to the reactor (1); the temperature of the reaction liquid is 180-220 ℃, and the temperature of the materials in the tower bottom of the heavy component tower (4) is 130-165 ℃.
3. The process method for preparing acetic acid by methanol carbonylation with the reactor thermally coupled with the rectifying tower according to claim 1, wherein reaction liquid in the reactor (1) passes through a first circulating pump (5) and then enters an external circulating heat exchanger (6) to exchange heat with desalted water (15) to generate heating steam, the reaction liquid at the outlet of the external circulating heat exchanger (6) returns to the reactor (1), the heating steam at the outlet of the circulating heat exchanger is sent to a kettle reboiler (14) of the heavy component tower (4) to heat kettle materials of the heavy component tower, and formed condensed water returns to the external circulating heat exchanger (6) to be used as desalted water (15) to exchange heat with the reaction liquid; the temperature of the reaction liquid is 180-220 ℃, the temperature of the heating steam is 160-200 ℃, and the temperature of the material in the bottom of the heavy component tower (4) is 130-165 ℃.
4. The process method for preparing acetic acid by methanol carbonylation with the reactor thermally coupled with the rectifying tower according to claim 1, wherein the gas phase component obtained by flash evaporation in the flash evaporator (2) enters the catalyst catcher (16), the caught catalyst returns to the bottom of the flash evaporator (2), and the gas phase enters the light component tower (3) for separation.
5. The process for preparing acetic acid by carbonylation of methanol with thermal coupling of a reactor and a rectifying tower as claimed in claim 4, wherein the catalyst catcher (16) is internally provided with a gas phase component washing device and a foam removing device; the gas-phase component washing device comprises an atomizer, and liquid-phase materials from the top of the light component tower (3) are introduced into the atomizer; the defoaming device comprises a fiber web.
6. The process for preparing acetic acid by methanol carbonylation with a reactor thermally coupled with a rectifying tower is characterized in that an acetic acid product is obtained from the middle side of the heavy component tower (4), and a second tower top light component at the tower top is returned to the middle of the light component tower (3).
7. The process for preparing acetic acid by carbonylation of methanol with thermally coupled reactor and rectifying tower as claimed in claim 6, wherein the heavy component tower (4) has tray number of 60-100, operating pressure of-0.05-0.2 MPaG in the tower, and temperature of the top of the tower is 100-; and the acetic acid product is extracted from the tower trays on the 2 nd to 8 th layers.
8. The process for preparing acetic acid by carbonylation of methanol with thermal coupling of a reactor and a rectifying tower as claimed in claim 1, wherein the number of trays of the light component tower (3) is 50-80, the operating pressure in the tower is 0.05-0.2MPaG, the temperature at the top of the tower is 90-140 ℃, and the temperature at the bottom of the tower is 145-165 ℃.
9. The process method for preparing acetic acid by methanol carbonylation with thermally coupled reactor and rectifying tower as claimed in claim 1, wherein the gas phase at the top of the light component tower (3) enters a condenser for condensation and then enters a reflux tank for gas-liquid separation to obtain non-condensable gas, the non-condensable gas enters an absorption tower, part of the liquid phase material returns to the reaction kettle through a second circulating pump (6), the second circulating pump (6) is a variable frequency pump, and the density of the working medium of the variable frequency pump is 1000-2000 kg/m-3。
10. The process method for preparing acetic acid by methanol carbonylation with the reactor thermally coupled with the rectifying tower is characterized in that the first overhead light component of the light component tower (3) enters a condenser and then enters a liquid-liquid separator for separation to obtain a liquid phase heavy phase, a liquid phase light phase and a gas phase component, part of the liquid phase heavy phase, the liquid phase light phase and the gas phase component are respectively sent back to the reactor (1) by a third circulating pump and a fourth circulating pump, and the gas phase component enters an absorption tower; the working medium density of the third circulating pump is 1200-2200 kg/m3The density of the working medium of the fourth circulating pump is 800-1500 kg/m3。
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| PCT/CN2020/111555 WO2021047392A1 (en) | 2019-09-10 | 2020-08-27 | Process method for preparing acetic acid by carbonylating methanol by means of reactor thermally coupled with rectifying tower |
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