CN110642969B - Pre-dehydration process of chloromethane - Google Patents
Pre-dehydration process of chloromethane Download PDFInfo
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- CN110642969B CN110642969B CN201910967761.7A CN201910967761A CN110642969B CN 110642969 B CN110642969 B CN 110642969B CN 201910967761 A CN201910967761 A CN 201910967761A CN 110642969 B CN110642969 B CN 110642969B
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F210/00—Copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond
- C08F210/04—Monomers containing three or four carbon atoms
- C08F210/08—Butenes
- C08F210/10—Isobutene
- C08F210/12—Isobutene with conjugated diolefins, e.g. butyl rubber
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C17/00—Preparation of halogenated hydrocarbons
- C07C17/38—Separation; Purification; Stabilisation; Use of additives
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C17/00—Preparation of halogenated hydrocarbons
- C07C17/38—Separation; Purification; Stabilisation; Use of additives
- C07C17/383—Separation; Purification; Stabilisation; Use of additives by distillation
Abstract
The invention relates to the technical field of chemical industry, in particular to a pre-dehydration process of chloromethane. The pre-dehydration process of methyl chloride comprises the following steps: A) the chloromethane and the triethylene glycol solution are contacted and absorbed in an absorption tower to obtain the predehydrated chloromethane; B) heating the rich solution after contact absorption to 70-90 ℃ for flash evaporation; C) heating the flash-evaporated rich solution to 130-220 ℃, regenerating, and carrying out steam stripping and cooling on the regenerated barren solution, and then carrying out anion exchange and reusing the barren solution in an absorption tower. The chloromethane and triethylene glycol solution are in countercurrent contact on the surface of a filler in an absorption tower, so that the predehydration of the chloromethane is completed, the absorbed rich solution is subjected to flash evaporation and regeneration at a specific temperature, and the obtained barren solution is subjected to steam stripping and cooling, and then subjected to anion exchange and reused in the absorption tower. The pre-dehydration process of methyl chloride provided by the invention solves the problems of corrosion and entrainment of absorption tower, the dehydration effect is excellent, and the triethylene glycol pre-dehydration system can continuously and stably operate.
Description
Technical Field
The invention relates to the technical field of chemical industry, in particular to a pre-dehydration process of chloromethane.
Background
The existing butyl rubber devices in China use alumina to dehydrate the circulating gas chloromethane, and the strong adsorbability of the alumina is utilized to reduce the water content in the circulating gas chloromethane to below 10ppm by adsorption. The use of activated alumina for dehydration can substantially meet the requirements of the production process, but there are also many problems: firstly, because the circulating chloromethane entering the drying tower has high water content, about 3000ppm, the drying tower is used for about 40 hours, and then the adsorption is saturated. The adsorption regeneration of the drying tower is intermittent operation, and the switching operation is carried out every 40 hours, so that the water value of the methyl chloride fluctuates, and the stable operation of the polymerization reaction is influenced; secondly, the regeneration is frequent, a large amount of hot nitrogen and heating steam are used in the regeneration period, the operation cost is high, and meanwhile, considerable chloromethane is lost in each regeneration, so that the environmental pollution is serious; and thirdly, due to frequent regeneration and short service life, the agent replacement operation is required every year, and the production is influenced.
In the existing production, some petrochemical plant butyl rubber devices have 3 drying towers in total, and during normal production, 1 production is carried out, 1 standby is carried out, and 1 regeneration is carried out. Some companies adopt 4 dryers for the methyl chloride dehydration process of a butyl rubber device, 1 dryer is operated, one dryer is regenerated, and 2 dryers are reserved. Because the water content in the circulating gas is high, the operation period of the alumina is short, and the energy consumption and material consumption are high. The industry needs a new dehydration process which can reduce the energy consumption and material consumption in the production of butyl rubber and reduce the damage to the environment.
Triethylene glycol (TEG), also known as triethylene glycol ether, has the characteristics of good stability, strong water absorption, easy regeneration at high temperature, low viscosity, low solubility in liquid hydrocarbons, low evaporation and small loss by gas entrainment, and the like, so TEG is used in a natural gas dehydrating agent in many devices. The foreign TEG dehydration process technology makes a series of progress in the aspects of improving dehydration depth, developing and applying novel and efficient dehydration equipment, improving glycol regeneration process, controlling regeneration tail gas pollution and the like. The common TEG dehydration device is mainly divided into an absorption part and a regeneration part, and applies the principles of absorption, separation, gas-liquid contact, mass transfer, heat transfer, extraction and the like, wherein the dew point can reach 30-60 ℃ usually, and the highest dew point can reach 85 ℃.
However, the dewatering effect of the existing TEG dewatering device is to be improved, and meanwhile, TEG is seriously polluted and deteriorated, so that foaming is caused, and the smooth operation of the dewatering process is influenced.
Disclosure of Invention
In view of the above, the technical problem to be solved by the present invention is to provide a pre-dehydration process for methyl chloride, which has a good dehydration effect and can be continuously and stably operated.
The invention provides a pre-dehydration process of chloromethane, which comprises the following steps:
A) the chloromethane and the triethylene glycol solution are contacted and absorbed in an absorption tower to obtain the predehydrated chloromethane;
B) heating the rich solution after contact absorption to 70-90 ℃ for flash evaporation;
C) heating the flash-evaporated rich solution to 130-220 ℃, regenerating, and carrying out steam stripping and cooling on the regenerated barren solution, and then carrying out anion exchange and reusing the barren solution in an absorption tower.
Preferably, the absorption tower comprises a feed distributor, and the feed distributor is rotatably arranged at the outlet of a feed pipe of the absorption tower and is used for uniformly distributing the triethylene glycol solution on the packing.
Preferably, the feeding distributor comprises a plurality of conducting pipes which are distributed along the inlet of the feeding distributor in the same direction;
the conduction pipes which are distributed in the same direction are on the same plane, and the plane where the conduction pipes are located is vertical to the tower body of the absorption tower;
the conduction pipe is provided with spray holes which are distributed at equal intervals along the conduction pipe.
Preferably, the tail ends of the conduction pipes are closed, the inlets of the conduction pipes are communicated, and the inlets of the conduction pipes are communicated with the inlet of the feeding distributor.
Preferably, the purity of the triethylene glycol solution is more than or equal to 98 percent.
Preferably, the flow rate of the methyl chloride gas is 20-30 t/h, and the flow rate of the triethylene glycol solution is 2.5-3 t/h.
Preferably, the stripping medium used for the stripping comprises hydrocarbons of C1-C6.
Preferably, the stripping medium used for the stripping comprises one or more of hexane, pentane, propane and chloromethane.
Preferably, the temperature after cooling is 45-65 ℃.
Preferably, the anion exchange is carried out in a resin filter;
the resin filter comprises macroporous polystyrene weak base anion resin or macroporous strong base anion resin.
The invention provides a pre-dehydration process of chloromethane, which comprises the following steps: A) the chloromethane and the triethylene glycol solution are contacted and absorbed in an absorption tower to obtain the predehydrated chloromethane; B) heating the rich solution after contact absorption to 70-90 ℃ for flash evaporation; C) heating the flash-evaporated rich solution to 130-220 ℃, regenerating, and carrying out steam stripping and cooling on the regenerated barren solution, and then carrying out anion exchange and reusing the barren solution in an absorption tower. Methyl chloride enters the absorption tower from the tower bottom of the absorption tower, triethylene glycol solution enters the absorption tower from the tower top of the absorption tower, the methyl chloride and the triethylene glycol solution are in countercurrent contact on the surface of a filler in the absorption tower, so that the pre-dehydration of the methyl chloride is completed, the absorbed rich solution is subjected to flash evaporation and regeneration at a specific temperature, and the obtained barren solution is subjected to steam stripping and cooling, then subjected to anion exchange and reused in the absorption tower. The pre-dehydration process of methyl chloride provided by the invention solves the problems of corrosion and entrainment of absorption tower, the dehydration effect is excellent, and the triethylene glycol pre-dehydration system can continuously and stably operate.
Experimental results show that in the operation of the pre-dehydration process for methyl chloride provided by the invention, the first heater, the second heater and the cooler can be operated for a long period of 20 months, and no obvious corrosion phenomenon can be realized. The dehydration capacity of the chloromethane predehydration process is close to the dehydration level of alumina, and the dehydration rate is higher than 99.7%, so that the regeneration period of the alumina drying tower is greatly prolonged, and the stable operation days are not less than 15 days.
Drawings
FIG. 1 is a schematic diagram of an absorption column according to an embodiment of the present invention;
FIG. 2 is a diagram of a pre-dehydration process for methyl chloride provided in accordance with an embodiment of the present invention;
fig. 3 is a schematic structural diagram of a conventional absorption tower according to a comparative example of the present invention.
Detailed Description
The technical solutions of the present invention will be described clearly and completely with reference to the following embodiments of the present invention, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention provides a pre-dehydration process of chloromethane, which comprises the following steps:
A) the chloromethane and the triethylene glycol solution are contacted and absorbed in an absorption tower to obtain the predehydrated chloromethane;
B) heating the rich solution after contact absorption to 70-90 ℃ for flash evaporation;
C) heating the flash-evaporated rich solution to 130-220 ℃, regenerating, and carrying out steam stripping and cooling on the regenerated barren solution, and then carrying out anion exchange and reusing the barren solution in an absorption tower.
In the invention, the chloromethane and the triethylene glycol solution are contacted and absorbed in an absorption tower to obtain the predehydrated chloromethane.
In the embodiment of the invention, the water content of the chloromethane is 2000-3000 ppm. In certain embodiments of the invention, the water content of the methyl chloride is 2800 ppm.
In an embodiment of the present invention, the absorption tower comprises:
a tower body of the absorption tower;
the feeding pipe and the gas outlet are arranged at the top of the tower body;
a feeding distributor rotatably connected with the discharge pipe mouth of the feeding pipe;
the filler device is arranged in the middle of the tower body;
and the gas inlet and the rich liquid outlet are arranged at the bottom of the tower body.
The structure of the absorption tower is shown in figure 1. Fig. 1 is a schematic structural view of an absorption tower according to an embodiment of the present invention. The left drawing in fig. 1 is a front view of the absorption column, and the right drawing in fig. 1 is a structural view of the feed distributor. Wherein, 1 is the absorption tower body, 2 is the inlet pipe, 3 is the feeding distributor, 4 is the filler device, 5 is the gas inlet, 6 is the rich liquid export, 7 is the gas outlet.
In certain embodiments of the invention, the absorption column is a packed column. The absorption tower comprises an absorption tower body 1. The material of the absorption tower body is not particularly limited in the present invention, and may be a material of the absorption tower body known to those skilled in the art. In some embodiments of the invention, the absorber tower body has the same shape and size as existing commercial absorber towers.
The absorption tower also comprises a feeding pipe 2 arranged at the top of the tower body. The feed pipe is used for inputting the triethylene glycol solution into the absorption tower. The material of the feeding pipe is not particularly limited in the present invention, and the material of the feeding pipe known to those skilled in the art may be adopted.
The absorption tower also comprises a feeding distributor 3 which is rotationally connected with the discharge pipe opening of the feeding pipe. For evenly distributing the triethylene glycol solution on the filler.
In some embodiments of the present invention, the feeding distributor includes a plurality of conducting pipes 3-1, the conducting pipes are distributed along the inlet of the feeding distributor, and the conducting pipes are provided with spray holes 3-2. As shown in the right drawing of fig. 1. In some embodiments, the conduction pipes distributed in the same direction are on the same plane, and the plane where the conduction pipes are located is perpendicular to the tower body of the absorption tower. In some embodiments, the number of conduction tubes is 6. In some embodiments, the orifices are equally spaced along the conduit.
In certain embodiments of the invention, the ends of the plurality of conducting tubes are closed, the inlets of the plurality of conducting tubes are in communication, and the inlets of the plurality of conducting tubes are in communication with the inlet of the feed distributor.
In certain embodiments of the invention, the feed distributor is rotationally coupled to the feed tube by a rotating shaft. The rotating shaft is a hollow rotating shaft, and triethylene glycol solution from the feeding pipe enters the feeding distributor through the rotating shaft.
Under the effect of pressure difference, triethylene glycol solution is spouted from the orifice of a plurality of pipes, and the reaction force that provides makes feeding distributor autogiration, can evenly distribute high viscosity triethylene glycol solution on packing, prevents that partial circulating gas from not absorbing through triethylene glycol and discharging from the top of the tower promptly, has strengthened tower gas-liquid exchange's effect, prevents that the entrainment from smuggleing secretly. Meanwhile, a trace amount of triethylene glycol solution flows out from a gap at the rotary joint to form a liquid seal, and the lubricating function is achieved.
The absorption tower also comprises a filler device 4 arranged in the middle of the tower body. The structure and source of the packing device are not limited in the present invention, and the packing device known to those skilled in the art may be used, and may be generally commercially available. In some embodiments of the present invention, the packing device is a commercially available pall ring packing, and the manufacturer may select Jiangxi Nuanxiang Longfa industries GmbH, Sulsho, etc. The methyl chloride and triethylene glycol solution are in countercurrent contact on the surface of the packing in the absorption tower, so that the pre-dehydration of the methyl chloride is completed.
The absorption tower also comprises a gas inlet 5 arranged at the bottom of the tower body. The methyl chloride gas to be dehydrated enters the absorption tower from a gas inlet at the bottom of the tower body of the absorption tower.
The absorption tower also comprises a rich liquid outlet 6 arranged at the bottom of the tower body. The rich liquid absorbing the moisture is discharged from a rich liquid outlet at the bottom of the absorption tower.
The absorption tower also comprises a gas outlet 7 arranged at the top of the tower body. And discharging the predehydrated methyl chloride from the top of the absorption tower. In certain embodiments of the invention, the pre-dehydrated methyl chloride enters a subsequent activated alumina dehydration process.
In certain embodiments of the invention, the triethylene glycol solution has a purity of 98% or greater. In certain embodiments of the invention, the triethylene glycol solution is 99% pure.
In some embodiments of the present invention, the flow rate of the methyl chloride gas is 20 to 30 t/h. In certain embodiments of the invention, the flow rate of the methyl chloride gas is 20t/h or 30 t/h.
In some embodiments of the invention, the flow rate of the triethylene glycol solution is 2.5 to 3 t/h. In certain embodiments of the invention, the flow rate of the triethylene glycol solution is 2.5t/h or 3 t/h.
In some embodiments of the present invention, the triethylene glycol solution has a pressure of 490 to 510kpa and a temperature of 28 to 32 ℃. In certain embodiments, the triethylene glycol solution has a pressure of 500kpa and a temperature of 30 ℃.
After the contact absorption is finished in the absorption tower, heating the rich solution after the contact absorption to 70-90 ℃ for flash evaporation. After flash evaporation, part of moisture in the rich solution and part of absorbed methyl chloride are converted into gas phase, and then are separated from the rich solution. In certain embodiments of the invention, the heating is performed in a first heater. The first heater of the present invention is not particularly limited in its structure and source, and may be any heater known to those skilled in the art, and may be commercially available. In the invention, the rich solution after contact absorption is heated to 70-90 ℃. In certain embodiments of the invention, the rich liquor after contact absorption is heated to 70 ℃ or 90 ℃.
In certain embodiments of the invention, the flashing is performed in a flash tank. The structure and the source of the flash tank are not particularly limited in the present invention, and the structure of the flash tank known to those skilled in the art may be adopted, and may be generally commercially available. In certain embodiments of the invention, the converted vapor phase may be fed into a recycle gas network.
And after the flash evaporation is finished, heating the flash evaporated rich solution to 130-220 ℃, regenerating, and performing steam stripping and cooling on the regenerated barren solution, and performing anion exchange on the barren solution to reuse the barren solution in the absorption tower.
In certain embodiments of the invention, the heating of the flashed rich liquid is performed in a second heater. The structure and source of the second heater are not particularly limited in the present invention, and the structure of the heater known to those skilled in the art may be adopted, and may be generally commercially available. In the invention, the flash-evaporated rich solution is heated to 130-220 ℃. In certain embodiments of the invention, the flashed rich liquid is heated to 130 ℃ or 220 ℃.
In certain embodiments of the present invention, the flashed rich liquid is pressurized via a first solution pump and then delivered to a second heater. In some embodiments of the present invention, the pressure of the first solution pump is 300 to 600 kpa. In certain embodiments of the invention, the first solution pump pressurizes at 350kpa or 550 kpa. The structure and source of the first solution pump are not particularly limited, and a solution pump known to those skilled in the art may be used, and the first solution pump may be generally commercially available.
And regenerating the flash-evaporated rich solution, and removing most of absorbed water in a form of water vapor to obtain a lean solution. In certain embodiments of the invention, the regeneration is performed in a regenerator. The structure and source of the regenerator are not particularly limited in the present invention, and any regenerator known to those skilled in the art may be used, and any regenerator is generally commercially available. In certain embodiments of the invention, a substantial portion of the water vapor removed from the regeneration is vented from the regenerator and may be stored for reuse. In certain embodiments of the invention, the water content of the regenerated lean liquor is less than or equal to 5000 ppm.
Stripping can remove residual moisture from the triethylene glycol solution. In certain embodiments of the invention, the stripping medium employed for the stripping comprises C1-C6 hydrocarbons. In certain embodiments, the stripping medium employed for the stripping comprises one or more of hexane, pentane, propane, and methyl chloride. In certain embodiments of the invention, the stripping is performed in a stripper. The structure and the source of the stripping tower are not particularly limited in the present invention, and the stripping tower known to those skilled in the art can be used, and can be generally commercially available. In certain embodiments of the invention, the stripping medium after completion of stripping, as well as the stripped residual moisture, may be fed into the recycle gas network. In certain embodiments of the invention, the temperature of the stripping is 120 to 210 ℃. In certain embodiments of the invention, the temperature of the stripping is 180 ℃.
In certain embodiments of the present invention, the regenerated lean liquor is pressurized via a second solution pump and then sent to a stripper. In some embodiments of the present invention, the second solution pump pressurizes the second solution at a pressure of 400 to 600 kpa. In certain embodiments of the invention, the second solution pump pressurizes at a pressure of 500 kpa. The structure and source of the second solution pump are not particularly limited, and a solution pump known to those skilled in the art may be used, and the second solution pump may be generally commercially available.
The invention further adopts a special stripping medium for stripping, which not only has the effects of reducing partial pressure and enhancing the water removal capacity, but also can enter a circulating gas pipe network along with steam after stripping, and can be separated after reaching the solvent recovery section of the butyl rubber without influencing the polymerization reaction of the butyl rubber.
In some embodiments of the present invention, the temperature after cooling is 45-65 ℃. In certain embodiments of the invention, the cooled temperature is 50 ℃. In certain embodiments of the invention, the cooling is performed in a chiller. The structure and source of the cooler are not particularly limited, and any cooler known to those skilled in the art may be used, and any cooler may be generally commercially available.
In certain embodiments of the invention, the stripped lean solution is pressurized via a third solution pump and then delivered to a cooler. In some embodiments of the present invention, the third solution pump pressurizes the solution at a pressure of 300 to 700 kpa. In certain embodiments of the invention, the third solution pump pressurizes at 350kpa or 650 kpa. The structure and source of the third solution pump are not particularly limited, and a solution pump known to those skilled in the art may be used, and the third solution pump may be generally commercially available.
After completion of cooling, anion exchange was performed. In certain embodiments of the invention, the anion exchange is performed in a resin filter. In certain embodiments of the invention, the resin filter is a macroporous anion exchange resin. In certain embodiments of the invention, the resin filter comprises a macroporous polystyrene type weak base anion resin or a macroporous strong base anion resin. In certain embodiments of the invention, the resin filter is a macroporous polystyrene type weak base anion resin or a macroporous strong base anion resin manufactured by blantt corporation.
The Cl in the triethylene glycol-depleted solution can be exchanged through anion exchange-Exchange to OH-Prevention of Cl-Causes corrosion of stainless steel equipment. After anion exchange, the obtained triethylene glycol-poor solution is reused for absorptionAnd (5) collecting the tower.
In certain embodiments of the present invention, the anion-exchanged lean triethylene glycol solution is stored in a buffer tank and then pressurized by a fourth solution pump for reuse in the absorption column.
The structure and source of the buffer tank are not particularly limited, and the buffer tank known to those skilled in the art may be used, and may be generally commercially available. In some embodiments of the present invention, the fourth solution pump pressurizes the solution at a pressure of 400 to 600 kpa. In certain embodiments of the present invention, the fourth solution pump pressurizes at a pressure of 500 kpa. The structure and source of the fourth solution pump are not particularly limited, and a solution pump known to those skilled in the art may be used, and the fourth solution pump may be generally commercially available.
Fig. 1 is a diagram of a pre-dehydration process of methyl chloride according to an embodiment of the present invention.
And (2) allowing the methyl chloride to be dehydrated to enter the absorption tower from the tower kettle of the absorption tower, allowing the triethylene glycol solution to enter the absorption tower from the tower top of the absorption tower, allowing the triethylene glycol solution and the absorption tower to be in countercurrent contact on the surface of a filler in the absorption tower, thereby completing the pre-dehydration of the methyl chloride, and discharging the pre-dehydrated methyl chloride from the tower top of the absorption tower to enter a subsequent dehydration process. The rich liquid absorbing the moisture is discharged from a rich liquid outlet at the bottom of the absorption tower. The rich liquid after contact absorption is heated in the first heater and then enters the flash tank for flash evaporation, part of moisture in the rich liquid and part of absorbed methyl chloride are converted into gas phase, and then the gas phase is separated from the rich liquid, discharged from the top of the flash tank and can be conveyed into a circulating gas pipe network. And pressurizing the flashed rich solution by a first solution pump, conveying the flashed rich solution to a second heater, heating the flashed rich solution in the second heater, then feeding the flashed rich solution into a regeneration tank for regeneration, discharging most of water vapor removed by regeneration from a regenerator, and storing and recycling the water vapor. The regenerated barren solution is pressurized by a second solution pump and is conveyed to a stripping tower for stripping, a stripping medium adopted by the stripping comprises C1-C6 hydrocarbons, the effects of reducing partial pressure and enhancing the water removal capacity are achieved, the medium can enter a circulating gas pipe network along with steam after the stripping, and can be separated after reaching a solvent recovery section of the butyl rubber without influencingThe polymerization of the butyl rubber is carried out. Pressurizing the stripped lean solution by a third solution pump, conveying the lean solution into a cooler, feeding the cooled lean solution into a resin filter for anion exchange, and carrying out Cl in the lean triethylene glycol solution-Exchange to OH-Prevention of Cl-Causes corrosion of stainless steel equipment. After anion exchange, the resulting triethylene glycol-lean solution can be stored in a buffer tank and pressurized via a fourth solution pump for reuse in the absorption column.
The pre-dehydration process of methyl chloride provided by the invention solves the problems of corrosion and entrainment of absorption tower, the dehydration effect is excellent, and the triethylene glycol pre-dehydration system can continuously and stably operate.
Experimental results show that in the operation of the pre-dehydration process for methyl chloride provided by the invention, the first heater, the second heater and the cooler can be operated for a long period of 20 months, and no obvious corrosion phenomenon can be realized. The dehydration capacity of the chloromethane predehydration process is close to the dehydration level of alumina, and the dehydration rate is higher than 99.7%, so that the regeneration period of the alumina drying tower is greatly prolonged, and the stable operation days are not less than 15 days.
In order to further illustrate the present invention, the process for the pre-dehydration of methyl chloride provided by the present invention is described in detail below with reference to examples, but they should not be construed as limiting the scope of the present invention.
The starting materials used in the following examples are all generally commercially available.
Example 1
Methyl chloride (flow rate is 20t/h, water content is 2800ppm) to be dehydrated enters the absorption tower from the tower bottom of the absorption tower (the absorption tower shown in figure 1 is adopted), triethylene glycol solution (purity is 99%, flow rate is 2.5t/h, pressure is 500kpa, temperature is 30 ℃) enters the absorption tower from the tower top of the absorption tower, the triethylene glycol solution and the triethylene glycol solution are in countercurrent contact on the surface of a filler in the absorption tower, so that the pre-dehydration of the methyl chloride is completed, the methyl chloride after the pre-dehydration is discharged from the tower top of the absorption tower and enters the subsequent dehydration process. The rich liquid absorbing the moisture is discharged from a rich liquid outlet at the bottom of the absorption tower. And heating the rich liquid after contact absorption to 70 ℃ in a first heater, then entering a flash tank, carrying out flash evaporation at 70 ℃, converting part of moisture in the rich liquid and part of absorbed methyl chloride into gas phase, separating the gas phase from the rich liquid, discharging the gas phase from the top of the flash tank, and conveying the gas phase into a circulating gas pipe network. And pressurizing the flashed rich solution to 350kpa through a first solution pump, conveying the flashed rich solution to a second heater, heating the flashed rich solution to 130 ℃ in the second heater, then entering a regeneration tank, regenerating at 130 ℃, discharging most of water vapor removed by regeneration from a regenerator, and storing for reuse. Pressurizing the regenerated lean solution to 500kpa by a second solution pump, conveying the lean solution to a stripping tower for stripping, wherein the stripping temperature is 180 ℃, stripping media adopted by stripping comprise hexane and pentane, pressurizing the stripped lean solution to 350kpa by a third solution pump, conveying the lean solution to a cooler, cooling the lean solution to 50 ℃, allowing the cooled lean solution to enter a resin filter (macroporous polystyrene weak base anion resin) for anion exchange, and after anion exchange, storing the obtained lean triethylene glycol solution in a buffer tank, pressurizing the lean triethylene glycol solution to 500kpa by a fourth solution pump, and recycling the lean solution to an absorption tower.
In this example, after the pre-dehydration process of methyl chloride was performed for a period of time, the corrosion conditions of the first heater, the second heater and the cooler were counted, as shown in table 1.
TABLE 1 Corrosion of the primary heater, secondary heater and cooler in example 1 during system operation
It can be seen from table 1 that in this condition, three important heat exchangers (including two heaters and coolers) were operated for a long period of 20 months without significant corrosion.
In this example, the water content of methyl chloride discharged from the top of the absorption tower was monitored, as shown in table 2.
TABLE 2 Water content of methyl chloride after predehydration
| Run time | Water content (ppm) |
| 10min | 5 |
| 30min | 5 |
| |
5 |
| |
5 |
| 3 |
5 |
| One |
5 |
| Two |
5 |
| One |
5 |
As can be seen from table 2, the methyl chloride discharged from the top of the absorption column had a lower water content and was stable, indicating that entrainment was low. The reformed triethylene glycol system is stable in operation, the dehydration capacity is close to the dehydration level of alumina, and the dehydration rate is higher than 99.7%, so that the regeneration period of the alumina drying tower is greatly prolonged, and the stable operation days are not less than 15 days.
Example 2
Methyl chloride (with the flow rate of 30t/h and the water content of 2800ppm) to be dehydrated enters an absorption tower (adopting the absorption tower shown in figure 1) from the tower bottom of the absorption tower, triethylene glycol solution (with the purity of 99 percent, the flow rate of 3t/h, the pressure of 500kpa and the temperature of 30 ℃) enters the absorption tower from the tower top of the absorption tower, the triethylene glycol solution and the triethylene glycol solution are in countercurrent contact on the surface of a filler in the absorption tower, so that the pre-dehydration of the methyl chloride is completed, the pre-dehydrated methyl chloride is discharged from the tower top of the absorption tower and enters a subsequent dehydration process. The rich liquid absorbing the moisture is discharged from a rich liquid outlet at the bottom of the absorption tower. And heating the rich liquid after contact absorption to 90 ℃ in a first heater, then entering a flash tank, carrying out flash evaporation at 90 ℃, converting part of moisture in the rich liquid and part of absorbed methyl chloride into gas phase, separating the gas phase from the rich liquid, discharging the gas phase from the top of the flash tank, and conveying the gas phase into a circulating gas pipe network. And pressurizing the flashed rich solution to 550kpa through a first solution pump, conveying the flashed rich solution to a second heater, heating the flashed rich solution to 220 ℃ in the second heater, then entering a regeneration tank, regenerating at 220 ℃, discharging most of water vapor removed by regeneration from a regenerator, and storing for reuse. Pressurizing the regenerated lean solution to 500kpa by a second solution pump, conveying the lean solution to a stripping tower for stripping, wherein the stripping temperature is 180 ℃, stripping media adopted by stripping comprise pentane, propane and methyl chloride, pressurizing the stripped lean solution to 650kpa by a third solution pump, conveying the lean solution to a cooler, cooling the lean solution to 50 ℃, feeding the cooled lean solution into a resin filter (macroporous strong base anion resin) for anion exchange, and after anion exchange, storing the obtained lean triethylene glycol solution in a buffer tank, pressurizing the lean triethylene glycol solution to 500kpa by a fourth solution pump, and recycling the lean solution to an absorption tower.
In this example, after the pre-dehydration process of methyl chloride was performed for a period of time, the corrosion conditions of the first heater, the second heater and the cooler were counted, as shown in table 3.
TABLE 3 Corrosion of the primary heater, secondary heater and cooler in example 2 during system operation
As can be seen from Table 3, the load of dehydration of triethylene glycol increases and the temperature of the regeneration column becomes high due to the increase of the circulation amount. But no significant corrosion occurred in both the first heater and the cooler. The second heater has extremely slight corrosion in the 20 th month, but the surface of the heat exchange tube is not smooth, and the thickness of the heat exchange tube is not changed obviously.
In this example, the water content of methyl chloride discharged from the top of the absorption column was monitored, as shown in table 4.
TABLE 4 Water content of methyl chloride after predehydration
| Run time | Water content (ppm) |
| 10min | 5 |
| 30min | 5 |
| |
5 |
| |
5 |
| 3 days | 6 |
| One |
5 |
| Two |
5 |
| One month | 6 |
As can be seen from table 4, the methyl chloride discharged from the top of the absorption column had a lower water content and was stable, indicating that entrainment was low. The reformed triethylene glycol system is stable in operation, the dehydration capacity is close to the dehydration level of alumina, and the dehydration rate is higher than 99.7%, so that the regeneration period of the alumina drying tower is greatly prolonged, and the stable operation days are not less than 15 days.
Comparative example 1
Methyl chloride (flow rate is 30t/h, water content is 2800ppm) to be dehydrated enters the absorption tower from the tower bottom of the absorption tower (the absorption tower shown in figure 3 is adopted), triethylene glycol solution (purity is 99%, flow rate is 3t/h, pressure is 500kpa, temperature is 30 ℃) enters the absorption tower from the tower top of the absorption tower, the triethylene glycol solution and the triethylene glycol solution are in countercurrent contact on the surface of a filler in the absorption tower, so that the pre-dehydration of the methyl chloride is completed, the pre-dehydrated methyl chloride is discharged from the tower top of the absorption tower and enters the subsequent dehydration process. The rich liquid absorbing the moisture is discharged from a rich liquid outlet at the bottom of the absorption tower. And heating the rich liquid after contact absorption to 90 ℃ in a first heater, then entering a flash tank, carrying out flash evaporation at 90 ℃, converting part of moisture in the rich liquid and part of absorbed methyl chloride into gas phase, separating the gas phase from the rich liquid, discharging the gas phase from the top of the flash tank, and conveying the gas phase into a circulating gas pipe network. And pressurizing the flashed rich solution to 550kpa through a first solution pump, conveying the flashed rich solution to a second heater, heating the flashed rich solution to 220 ℃ in the second heater, then entering a regeneration tank, regenerating at 220 ℃, discharging most of water vapor removed by regeneration from a regenerator, and storing for reuse. Pressurizing the regenerated lean solution to 500kpa by a second solution pump, conveying the lean solution to a stripping tower for stripping, wherein the stripping temperature is 180 ℃, stripping media adopted by stripping comprise pentane, propane and methyl chloride, pressurizing the stripped lean solution to 650kpa by a third solution pump, conveying the lean solution to a cooler, cooling the lean solution to 50 ℃, feeding the cooled lean solution into a resin filter (macroporous strong base anion resin) for anion exchange, and after anion exchange, storing the obtained lean triethylene glycol solution in a buffer tank, pressurizing the lean triethylene glycol solution to 500kpa by a fourth solution pump, and recycling the lean solution to an absorption tower.
Fig. 3 is a schematic structural diagram of a conventional absorption tower according to a comparative example of the present invention. The left drawing in fig. 3 is a front view of the absorption column, and the right drawing in fig. 3 is a structural view of a feed distributor which is a prior art employing a large number of feed distributors. Wherein, 01 is the absorption tower body, 02 is the inlet pipe, 03 is the feeding distributor, 04 is the packing device, 05 is the gas inlet, 06 is the rich liquid export, 07 is the gas outlet. The feeding distributor 03 is fixedly connected with the feeding pipe 02. The feeding distributor has uneven feeding distribution, and TEG may not have liquid exchange phenomenon in the existing place on the packing, so that the triethylene glycol absorption effect is poor, and the outlet water content of the circulating gas chloromethane is high.
In this comparative example, after the pre-dehydration process of methyl chloride was performed for a certain period of time, the corrosion conditions of the first heater, the second heater, and the cooler were counted, as shown in table 5.
TABLE 5 Corrosion of the first heater, the second heater and the cooler in comparative example 1 during the operation of the system
As can be seen from table 5, the three key heat exchangers described above (including two heaters and coolers) all showed different levels of corrosion at 20 months, especially the second heater, which even showed leakage due to high temperature.
The water content of methyl chloride discharged from the top of the absorption column was monitored in this comparative example, and is shown in table 6.
TABLE 6 Water content of methyl chloride after predehydration
| Run time | Water content (ppm) |
| 10min | 15 |
| 30min | 9 |
| 1h | 26 |
| 24h | 33 |
| 3 days | 18 |
| One week | 39 |
| Two weeks | 55 |
| One month | 40 |
As can be seen from Table 6, the water content of methyl chloride discharged from the top of the absorption column was extremely unstable, indicating entrainment due to uneven distribution of triethylene glycol in the packing, and a part of methyl chloride was not sufficiently mixed with triethylene glycol and dried. And the water absorption capacity of the lean triethylene glycol is low due to no stripping process.
Experimental results show that in the operation of the pre-dehydration process for methyl chloride provided by the invention, the first heater, the second heater and the cooler can be operated for a long period of 20 months, and no obvious corrosion phenomenon can be realized. The dehydration capacity of the chloromethane predehydration process is close to the dehydration level of alumina, and the dehydration rate is higher than 99.7%, so that the regeneration period of the alumina drying tower is greatly prolonged, and the stable operation days are not less than 15 days.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (7)
1. The pre-dehydration process of methyl chloride is characterized by comprising the following steps:
A) the chloromethane and the triethylene glycol solution are contacted and absorbed in an absorption tower to obtain the predehydrated chloromethane;
the absorption tower comprises a feeding distributor, and the feeding distributor is rotatably arranged at the outlet of a feeding pipe of the absorption tower and is used for uniformly distributing the triethylene glycol solution on the filler;
the feeding distributor comprises a plurality of conducting pipes which are distributed along the inlet of the feeding distributor in the same direction;
the conduction pipes which are distributed in the same direction are on the same plane, and the plane where the conduction pipes are located is vertical to the tower body of the absorption tower;
the conduction pipe is provided with spray holes which are distributed at equal intervals along the conduction pipe;
the tail ends of the conduction pipes are closed, the inlets of the conduction pipes are communicated, and the inlets of the conduction pipes are communicated with the inlet of the feeding distributor;
B) heating the rich solution after contact absorption to 70-90 ℃ for flash evaporation;
C) heating the flash-evaporated rich solution to 130-220 ℃, regenerating, and carrying out steam stripping and cooling on the regenerated barren solution, and then carrying out anion exchange and reusing the barren solution in an absorption tower.
2. The pre-dehydration process of methyl chloride according to claim 1, characterized in that the purity of the triethylene glycol solution is 98% or more.
3. The pre-dehydration process of methyl chloride according to claim 1, characterized in that the flow rate of the methyl chloride gas is 20 to 30t/h, and the flow rate of the triethylene glycol solution is 2.5 to 3 t/h.
4. The pre-dehydration process of methyl chloride according to claim 1, characterized in that the stripping medium used for the stripping comprises hydrocarbons from C1 to C6.
5. Process for the predehydration of methyl chloride as claimed in claim 4, wherein the stripping medium used for the stripping comprises one or several of hexane, pentane, propane and methyl chloride.
6. The pre-dehydration process of methyl chloride according to claim 1, characterized in that the temperature after cooling is 45-65 ℃.
7. The pre-dehydration process of methyl chloride according to claim 1, characterized in that said anion exchange is carried out in a resin filter;
the resin filter comprises macroporous polystyrene weak base anion resin or macroporous strong base anion resin.
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| CN101891857A (en) * | 2009-05-21 | 2010-11-24 | 中国石油化工股份有限公司 | Method for inhibiting corrosion of butyl rubber chloromethane glycol dehydration system |
| CN103725341A (en) * | 2012-10-11 | 2014-04-16 | 刘友利 | Dehydration process for purifying natural gas |
| CN107551769A (en) * | 2017-10-11 | 2018-01-09 | 成都赛普瑞兴科技有限公司 | A kind of vehicular glycol dehydration device and absorption system |
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