A process and device for preparing anhydrous formic acid

Abstract

The present invention discloses a preparation process and a preparation device for anhydrous formic acid, relating to the technical field of anhydrous formic acid preparation, and comprising a reboiler, a condenser, a liquid collection part, a cleaning part and a wire mesh demister. A preparation process for anhydrous formic acid is also disclosed, which comprises the following steps: feeding raw materials, purification, hydrolysis, separation, dehydration and collection. In the present invention, the reboiler is provided to heat the liquid, the heated liquid forms steam and rises upward, passes through the cooler, a part of the steam continues to rise upward and passes through the wire mesh demister to separate the liquid droplets in the steam, and another part of the liquid is liquefied and refluxed to the reboiler. After the liquid droplets in the steam are separated by the wire mesh demister, the liquid droplets flow into the liquid collection tank; when the pipeline in the condenser is blocked, the cleaning part is used to dredge the pipeline of the condenser and clean the dredged impurities into the liquid collection part, and the pipeline in the condenser is cleaned in a state of non-stop operation, thereby improving the working efficiency.

Description

Technical Field

[0001] The present invention belongs to the technical field of chemical reactions and separations, and particularly relates to a process and a device for preparing anhydrous formic acid. Background Art

[0002] Anhydrous formic acid is an organic compound with strong acidity. It is a colorless liquid with a pungent odor and is commonly used as a raw material and solvent in industrial production. Anhydrous formic acid is usually obtained by the hydrolysis of methyl formate during the manufacturing process. It has wide applications in fields such as chemical synthesis, leather treatment, food additives, and pharmaceutical production. Due to its strong acidity and reducibility, anhydrous formic acid serves as an important reactant in many reactions.

[0003] The patent with the publication number CN118439943A discloses a method for preparing industrial-grade formic acid by the hydrolysis of methyl formate. This method uses a reactive distillation dividing wall column for the hydrolysis reaction of methyl formate and the separation of formic acid and water; the reactive distillation dividing wall column includes a reactive distillation section, a common distillation section, a wastewater distillation section, and a crude acid stripping section. The pressurized reactive distillation dividing wall column is used for the reaction of hydrolyzing methyl formate to formic acid. The reactive distillation section is filled with a solid acid catalyst packing. Under the reaction conditions, it can effectively avoid the problem of difficult separation of the water and formic acid azeotrope, reduce the equipment cost and energy consumption. In the reactive distillation dividing wall column, under the catalytic action of the solid acid catalyst, the conversion rate of methyl formate is greater than 99%; moreover, the provided method can simultaneously complete the hydrolysis of methyl formate and the purification of the formic acid solution under a pressurized environment, reducing the equipment cost and the separation cost and energy consumption.

[0004] However, it is found in actual production that the above technical solution still has problems: in the above solution, the pipeline in the condenser is prone to blockage during use. The impurities carried by the steam when passing through the pipeline will accumulate inside it, resulting in pipeline blockage, causing the rising steam to accumulate in the distillation column. Since the steam continuously rises, the pressure in the distillation column continuously increases, leading to a decrease in the purity of product separation and causing the equipment pressure to exceed the standard, thus causing damage.

[0005] Therefore, it is very necessary to invent a process and a device for preparing anhydrous formic acid to solve the above problems. Summary of the Invention

[0006] The object of the present invention is to provide a process and a device for preparing anhydrous formic acid to solve the problems raised in the above background art in view of the existing technical problems.

[0007] The present invention provides an anhydrous formic acid preparation device, including a rectifying column; a hydrolysis reactor, the top of which is connected to the bottom of the rectifying column through a pipeline; a gas-liquid separator, the bottom of which is connected to the bottom of the hydrolysis reactor through a pipeline; a reaction kettle, the top of which is connected to the top of the gas-liquid separator through a pipeline; a dehydration device, the top of which is connected to the top of the rectifying column through a pipeline; a product collection tank, the top of which is connected to the bottom of the dehydration device through a pipeline; the rectifying column includes: a tower body; a reboiler, which is fixedly arranged at the bottom inside the tower body, and the reboiler can heat the liquid at the bottom inside the tower body to make the heated liquid evaporate into steam and rise; a condenser, which is fixedly arranged at the top inside the tower body, and the condenser can cool the rising steam; a liquid collection part, which is arranged inside the top of the condenser, and it can collect liquid droplets, and the collected liquid droplets flow back into the reboiler through the liquid collection part for heating; a cleaning part, which is arranged inside the condenser, and the cleaning part can move up and down inside the condenser and dredge the components in the condenser; a wire mesh demister, which is fixedly arranged at the top inside the tower body and above the condenser, and can separate the liquid droplets in the steam, and the separated liquid droplets are collected by the liquid collection part.

[0008] Preferably, the reboiler includes: an annular cylinder, which is fixedly arranged at the bottom inside the tower body; heat exchange tubes, which are fixedly arranged inside the annular cylinder and can heat the liquid; a high-temperature liquid inlet, which is connected to one end of the heat exchange tubes, and the other end of the high-temperature liquid inlet penetrates through the tower body and the annular cylinder hermetically and extends out of the outer wall of the tower body; a high-temperature liquid outlet, which is connected to one end of the heat exchange tubes, and the other end of the high-temperature liquid outlet penetrates through the tower body and the annular cylinder hermetically and extends out of the outer wall of the tower body, and the high-temperature liquid outlet and the high-temperature liquid inlet are in relative positions; a plurality of first air holes, which are arranged on the top of the annular cylinder; a heat insulation cavity, which is arranged inside the annular cylinder; a plurality of heating tubes, which are located between the tubes of the heat exchange tubes; a plurality of channels, which are fixedly arranged on the top of the heating tubes.

[0009] Preferably, the condenser includes: a condensation cylinder, which is arranged at the top of the tower body, and cooling water is arranged inside it to cool the steam; an air outlet pipe, which is fixedly arranged at the top of the condensation cylinder; a plurality of spiral tubes, the tops of which are connected to the air outlet pipe; and the bottoms of the plurality of spiral tubes are fixedly arranged at the bottom of the condensation cylinder; a concave conical groove, which is fixedly arranged at the bottom of the condensation cylinder; a plurality of air inlet holes, which are arranged between the concave conical groove and the condensation cylinder, and the tops of the plurality of air inlet holes are connected to the bottoms of the corresponding spiral tubes.

[0010] Preferably, the condenser further includes: an annular cylinder fixedly arranged at the top of the condensation cylinder; a plurality of second air outlet holes arranged on the top of the annular cylinder and staggered from the air outlet pipe; a sleeve, the inner wall of which is fixedly arranged with the outer wall of the condensation cylinder, and the outer wall of which is fixedly arranged at the top inside the tower body.

[0011] Preferably, the condenser further includes: a liquid inlet pipe communicated with one end of the condensation cylinder, and the other end thereof hermetically penetrates through the sleeve and the tower body and extends out of the outer wall of the tower body; a liquid outlet pipe communicated with one end of the condensation cylinder, and the other end thereof hermetically penetrates through the sleeve and the tower body and extends out of the outer wall of the tower body, and the liquid outlet pipe and the liquid inlet pipe are in opposite positions.

[0012] Preferably, the liquid collection part further includes: a collection cavity opened between the outer wall of the condensation cylinder and the inner wall of the sleeve and located at the top of the two; a filter screen arranged in the collection cavity; a plurality of leakage holes opened between the bottom of the annular cylinder and the connection part at the top of the condensation cylinder; a plurality of liquid leakage pipes, and the tops of the plurality of liquid leakage pipes are communicated with the top of the collection cavity.

[0013] Preferably, the cleaning part includes: a first annular cavity opened between the outer wall of the condensation cylinder and the inner wall of the sleeve and located in the middle of the two; a first annular plate hermetically and slidably arranged in the first annular cavity; a second annular cavity opened between the outer wall of the condensation cylinder and the inner wall of the sleeve and located at the bottom of the two; a second annular plate hermetically and slidably arranged in the second annular cavity; a plurality of springs fixedly arranged between the top of the second annular cavity and the top of the second annular plate; a plurality of connecting columns fixedly arranged at the bottom of the first annular plate.

[0014] Preferably, the cleaning part further includes: a round pipe, the bottom of which is embedded in the top of the condensation cylinder, and the top of which is higher than the top of the condensation cylinder; a plurality of nozzles fixedly arranged at the top of the round pipe, and the jet directions of the plurality of nozzles face the leakage holes; a plurality of air flow pipes, the tops of the plurality of air flow pipes are communicated with the bottom of the round pipe, and the bottoms of the plurality of air flow pipes are communicated with the bottom of the first annular cavity.

[0015] Preferably, the cleaning part further includes: a plurality of ventilation pipes corresponding to the spiral pipes, the tops of the plurality of ventilation pipes are communicated with the top of the first annular cavity, and the bottoms of the plurality of ventilation pipes are communicated with the bottoms of the corresponding spiral pipes; a plurality of solenoid valves corresponding to the spiral pipes, and the solenoid valves are fixedly arranged at the bottoms of the spiral pipes and are located below the ventilation pipes.

[0016] The present invention also discloses a preparation process of anhydrous formic acid, including the following steps:

[0017] Step 1, feeding raw materials, the raw materials react in the reaction kettle and generate a methyl formate mixed solution;

[0018] Step 2: Purification. The generated methyl formate mixture is purified in a gas-liquid separator to obtain methyl formate.

[0019] Step 3: Hydrolysis. Methyl formate is hydrolyzed in a hydrolysis reactor to obtain a mixed solution containing formic acid.

[0020] Step 4: Separation. Water and formic acid in the mixed solution are separated in a distillation column to obtain relatively pure anhydrous formic acid.

[0021] Step 5: Dehydration. Anhydrous formic acid enters a dehydration device in the form of steam to remove water.

[0022] Step 6: Collection. The anhydrous formic acid with water removed is collected in a product collection tank to obtain the final product.

[0023] The beneficial effects of the present invention are as follows:

[0024] 1. Through the cooperation of the first annular cavity, the first annular plate, the connecting column and the second annular plate, when the air pressure below the condenser increases, the electromagnetic valve closes the air inlet at the bottom of the spiral tube. At this time, the increased pressure pushes the second annular plate upward, causing the second annular plate to drive the first annular plate to slide in the first annular cavity through the connecting column, and squeezing the gas in the upper cavity. The squeezed gas enters the spiral tube through the ventilation pipe for dredging, and the impurities inside are discharged to the top of the condensation cylinder through the air outlet pipe, thereby improving the purity of product separation and realizing self-cleaning without shutting down the machine, thus improving the working efficiency.

[0025] 2. Through the cooperation of the first annular cavity, the first annular plate, the connecting column, the second annular plate and the spring, when the spiral pipeline is dredged, the pressure between the condenser and the reboiler is restored. The compressed spring drives the second annular plate downward. During the downward movement of the second annular plate, it drives the first annular plate to squeeze the gas in the lower cavity through the connecting column. The squeezed gas flows into the round tube through the air flow pipe and is ejected through the nozzle to clean the impurities cleared from the spiral tube at the top of the condensation cylinder, avoiding the influence on the droplet flow caused by the attachment of impurities on the protruding conical surface at the top of the condensation cylinder, thereby improving the droplet flow effect. Description of the Drawings

[0026] Figure 1 It is a schematic structural diagram of the anhydrous formic acid preparation device of the present invention.

[0027] Figure 2 It is a schematic sectional view of the distillation column of the present invention.

[0028] Figure 3 It is a schematic structural diagram of the reboiler of the present invention.

[0029] Figure 4 It is a schematic structural diagram of the condenser of the present invention.

[0030] Figure 5 It is a schematic cross-sectional structural diagram of the condenser of the present invention.

[0031] Figure 6 It is a schematic cross-sectional structural diagram of the liquid collection part in the present invention.

[0032] Figure 7 It is a schematic cross-sectional structural diagram of the cleaning part of the present invention.

[0033] Figure 8 It is a schematic diagram of the state when the first annular plate of the present invention is at the first height.

[0034] In the figure: 1, rectifying column; 2, hydrolysis reactor; 3, gas-liquid separator; 4, reaction kettle; 5, dehydration equipment; 6, product collection tank; 7, reboiler; 8, condenser; 9, liquid collection part; 10, cleaning part; 11, wire mesh demister; 12, tower body; 7001, annular cylinder; 7002, heat exchange tubes; 7003, high-temperature liquid inlet; 7004, high-temperature liquid outlet; 7005, first air outlet; 7006, heat insulation cavity; 7007, heating tube; 7008, channel; 8001, condensation cylinder; 8002, air outlet pipe; 8003, spiral tube; 8004, concave conical groove; 8005, air inlet hole; 8006, annular cylinder; 8007, second air outlet; 8008, sleeve; 8009, liquid inlet pipe; 8010, liquid outlet pipe; 9001, collection cavity; 9002, filter screen; 9003, leakage hole; 9004, liquid leakage pipe; 1001, first annular cavity; 1002, first annular plate; 1003, second annular cavity; 1004, second annular plate; 1005, spring; 1006, connecting column; 1007, round tube; 1008, nozzle; 1009, air flow pipe; 1010, ventilation pipe; 1011, solenoid valve. Specific embodiments

[0035] Next, the technical solutions in the embodiments of the present application will be clearly described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art belong to the scope protected by the present application.

[0036] Embodiment 1, the present invention provides as Figures 1 to 8An anhydrous formic acid preparation device shown in the figure includes a rectification column 1; a hydrolysis reactor 2, the top of which is connected to the bottom of the rectification column 1 through a pipeline; a gas-liquid separator 3, the bottom of which is connected to the bottom of the hydrolysis reactor 2 through a pipeline; a reaction kettle 4, the top of which is connected to the top of the gas-liquid separator 3 through a pipeline; a dehydration device 5, the top of which is connected to the top of the rectification column 1 through a pipeline; and a product collection tank 6, the top of which is connected to the bottom of the dehydration device 5 through a pipeline.

[0037] Put the raw materials into the reaction kettle 4 for reaction. After the reaction, a methyl formate mixed solution is generated. Subsequently, the reacted methyl formate mixed solution is introduced into the gas-liquid separator 3 through a pipeline, so that the reacted methyl formate mixed solution is purified by the gas-liquid separator 3. The purified methyl formate mixed solution generates methyl formate. The methyl formate is introduced into the hydrolysis reactor 2 through a pipeline, and the purified methyl formate is hydrolyzed to obtain a mixed solution containing formic acid. The hydrolyzed formic acid mixed solution is introduced into the rectification column 1 through a pipeline, and the formic acid mixed solution is separated to obtain relatively pure formic acid. The formic acid is introduced into the dehydration device 5 in the form of formic acid vapor through a pipeline, and water is removed in the dehydration device 5 to obtain anhydrous formic acid. The anhydrous formic acid flows through the pipeline into the product collection tank 6, and finally an anhydrous formic acid product is formed.

[0038] The distillation tower 1 comprises: a tower body 12; a reboiler 7, which is fixedly arranged at the bottom of the tower body 12, and the reboiler 7 can heat the liquid at the bottom of the tower body 12, so that the heated liquid evaporates and turns into steam to rise; it comprises an annular cylinder 7001, and a plurality of inclined holes are arranged in the top of the annular cylinder 7001 for discharging the droplets falling from the top, which is fixedly arranged at the bottom of the tower body 12, and a gap is reserved between the outer wall of the annular cylinder 7001 and the inner wall of the tower body 12, so that the droplets falling from the top of the annular cylinder 7001 can flow to the bottom of the annular cylinder 7001 through the gap, and a plurality of groups of fixed blocks are fixedly arranged on the outer side wall of the bottom of the annular cylinder 7001, and the plurality of groups of fixed blocks are fixed on the tower body 1 2 corresponding position of the inner wall at the bottom to fix the annular tube 7001; the heat exchange tube 7002 is fixedly arranged inside the annular tube 7001, which can heat the liquid. The heat exchange tube 7002 is composed of multiple groups of straight tubes and annular tubes. The multiple groups of annular tubes are located at the top and bottom of the corresponding multiple groups of straight tubes, and the multiple groups of straight tubes are in a connected state with the multiple groups of annular tubes. The high-temperature liquid flows into the straight tubes through the annular tubes at the bottom, and then flows into the annular tubes at the top, which is convenient for heating the liquid; the high-temperature liquid inlet 7003 is connected to one end of the heat exchange tube 7002, and the high-temperature liquid inlet 7003 is connected to the annular tube at the bottom of the straight tube, and the high-temperature liquid inlet 7003 is connected to the annular tube at the bottom of the straight tube. The other end is sealed and passes through the tower body 12 and the annular tube 7001 and extends out of the outer wall of the tower body 12, which is connected to the external high-temperature liquid pipeline and is used to provide high-temperature liquid to the heat exchange tube 7002; the high-temperature liquid outlet 7004 is connected to one end of the heat exchange tube 7002, the high-temperature liquid outlet 7004 is connected to the annular tube at the top of the straight tube, and the other end of the high-temperature liquid outlet 7004 is sealed and passes through the tower body 12 and the annular tube 7001 and extends out of the outer wall of the tower body 12, and its external connection is connected with a pipeline for discharging the high-temperature liquid in the heat exchange tube 7002, and the high-temperature liquid outlet 7004 is in a relative position to the high-temperature liquid inlet 7003. The port 7004 is used to replace the high-temperature liquid in the heat exchange tube 7002, further improving the effect of the heat exchange tube 7002 on heating the liquid; the first air outlet 7005 is provided with multiple groups and opened at the top of the annular tube 7001, and the multiple groups of first air outlets 7005 are staggered with the heating tube 7007 to prevent the liquid droplets from flowing into the heating tube 7007; the liquid droplets at the top of the annular tube 7001 are discharged through the inclined groove opened on the outer wall of the annular tube 7001; the heat insulation cavity 7006 can prevent the reboiler 7 from exchanging heat with the liquid outside the annular tube 7001, thereby improving the heating effect of the heat exchange tube 7002, and it is opened inside the annular tube 7001;The heating tubes 7007 are provided in multiple groups and are located between the tubes of the heat exchange tube bundles 7002. The top of the heating tubes 7007 is higher than the top of the heat exchange tube bundles 7002, and both the upper and lower ends of the heating tubes 7007 are in a through state. The liquid at the bottom of the tower body 12 enters the heating tubes 7007 from the bottom of the heating tubes 7007; a collection tank is formed between adjacent heating tubes 7007 and the top of the heat exchange tube bundles 7002, and this collection tank is aligned with the first air outlet 7005 for guiding the falling liquid droplets to be discharged; the channels 7008 are provided in multiple groups and are fixedly arranged at the top of the heating tubes 7007, and these channels 7008 are communicated with the collection tank; when the liquid flowing back from above drops, a part of the liquid flows through the top of the annular cylinder 7001 to the reserved gap between the outer wall of the annular cylinder 7001 and the inner wall of the tower body 12, and enters the bottom of the heating tubes 7007 through this gap for reheating; another part of the falling liquid drops into the collection tank through the first air outlet 7005, and the liquid is discharged into the reserved gap between the outer wall of the annular cylinder 7001 and the inner wall of the tower body 12 through the channels 7008 and the inclined groove, and enters the bottom of the heating tubes 7007 through this gap.;

[0039] The condenser 8 is fixedly arranged at the top inside the tower body 12, and the condenser 8 can cool the ascending steam. It includes a condensation cylinder 8001, the top of which is set as a protruding conical surface to facilitate the flow of liquid droplets to both sides. It is arranged at the top of the tower body 12, and there is cooling water inside it to cool the steam. An air outlet pipe 8002 is used for discharging the steam and is fixedly arranged at the top of the condensation cylinder 8001. The spiral pipe 8003 has a spiral outer shape, which can increase the contact area of the steam, so that the steam can obtain a better cooling effect. It is set in multiple groups, and the tops of multiple groups of spiral pipes 8003 are communicated with the air outlet pipe 8002. And the bottoms of multiple groups of spiral pipes 8003 are fixedly arranged with the bottom of the condensation cylinder 8001. A concave conical groove 8004 is fixedly arranged at the bottom of the condensation cylinder 8001 to guide the steam. A plurality of air inlet holes 8005 are arranged between the concave conical groove 8004 and the condensation cylinder 8001, and the tops of multiple groups of air inlet holes 8005 are communicated with the bottoms of the corresponding spiral pipes 8003. The steam is guided into the air inlet holes 8005 through the concave conical groove 8004, so that the steam in the air inlet holes 8005 enters the spiral pipes 8003. An annular cylinder 8006 is fixedly arranged at the top of the condensation cylinder 8001. A plurality of second air outlet holes 8007 are arranged at the top of the annular cylinder 8006, and multiple groups of second air outlet holes 8007 are staggered from the air outlet pipe 8002 to prevent liquid droplets from flowing into the spiral pipes 8003 through the air outlet pipe 8002, thus affecting the ascending of the steam. A sleeve 8008 has its inner wall fixedly arranged with the outer wall of the condensation cylinder 8001, and its outer wall is fixedly arranged at the top inside the tower body 12. A liquid inlet pipe 8009 is communicated with an external cooling pipeline to provide coolant for it. It is communicated with one end of the condensation cylinder 8001, and the other end seals through the sleeve 8008 and the tower body 12 and extends out of the outer wall of the tower body 12. A liquid outlet pipe 8010 is communicated with an external cooling pipe to discharge the coolant. It is communicated with one end of the condensation cylinder 8001, and the other end seals through the sleeve 8008 and the tower body 12 and extends out of the outer wall of the tower body 12. The liquid outlet pipe 8010 and the liquid inlet pipe 8009 are in opposite positions. Through the arrangement of the liquid inlet pipe 8009 and the liquid outlet pipe 8010, it is convenient to replace the coolant in the condensation cylinder 8001, so that the coolant always maintains the effect of cooling the steam.

[0040] The liquid collection part 9 is arranged inside the top of the condenser 8 and can collect the liquid droplets separated by the wire mesh demister 11. The collected liquid droplets flow back into the reboiler 7 through the liquid collection part 9 for heating. It includes a collection chamber 9001, which is opened between the outer wall of the condensation cylinder 8001 and the inner wall of the sleeve 8008 and is located at the top of both; a filter screen 9002, which is arranged in the collection chamber 9001 for filtering impurities; leakage holes 9003, which are arranged in multiple groups and are opened between the bottom of the annular cylinder 8006 and the connection part at the top of the condensation cylinder 8001. Due to the convex conical surface arranged at the top of the condensation cylinder 8001, it is convenient for the liquid droplets falling from above to flow and pass through the leakage holes 9003 into the collection chamber 9001; leakage liquid pipes 9004, which are arranged in multiple groups, and the tops of the multiple groups of leakage liquid pipes 9004 are communicated with the top of the collection chamber 9001. A one-way valve is arranged at the bottom of the leakage liquid pipe 9004. The liquid droplets in the collection chamber 9001 flow into the leakage liquid pipe 9004, and the liquid opens the one-way valve and flows into the bottom of the tower body 12 through the gap reserved between the outer wall of the annular cylinder 7001 and the inner wall of the tower body 12 for reheating and evaporation again.

[0041] The wire mesh demister 11 is fixedly arranged at the top inside the tower body 12 and above the condenser 8 and can separate the liquid droplets in the steam.

[0042] In summary, the formic acid mixed solution is introduced into the bottom of the tower body 12 through a pipeline and enters the heating pipe 7007. The heat exchange tube 7002 heats the liquid in the heating pipe 7007. After the liquid is heated to boiling, it forms steam. The steam is discharged through the first air outlet 7005 on the annular cylinder 7001 and rises. During the rising process, the steam will enter the air inlet hole 8005 along the concave conical groove 8004 and flow into the two groups of spiral tubes 8003 through the air inlet hole 8005 respectively, so that the steam is cooled. A part of the cooled steam becomes liquid and flows downward through the spiral tube 8003. During the reflux process of the condensed liquid, it contacts the rising steam, so that the light components such as formic acid are transferred from the liquid phase to the gas phase, and the heavy components such as water are transferred from the gas phase to the liquid phase, so that the liquid drops to the top of the annular cylinder 7001; another part of the steam continues to rise from the spiral tube 8003 and flows out through the air outlet pipe 8002. The steam flowing out enters the annular cylinder 8006, is discharged through the second air outlet 8007 above the annular cylinder 8006, and continues to rise and flow to the wire mesh demister 11. The wire mesh demister 11 removes the liquid droplets in the steam. The removed liquid droplets drop to the top of the annular cylinder 8006 or drop to the top of the condensation cylinder 8001 through the second air outlet 8007, and then flow to the collection chamber 9001. The liquid droplets in the collection chamber 9001 flow into the bottom of the tower body 12 through the leakage liquid pipe 9004 for reheating; while removing the liquid droplets in the steam, the steam flows through the outlet at the top of the tower body 12 into the dehydration device 5 to remove moisture and form the final anhydrous formic acid product.

[0043] Example 2. On the basis of the above example, due to the long-term use of the spiral tube 8003, impurities carried in the steam will accumulate inside it when passing through the spiral tube 8003, thus causing blockage of the spiral tube 8003, resulting in the accumulation of rising steam below the condenser 8. Since the steam continuously rises, the pressure inside the tower body 12 continuously increases, causing the purity of product separation to decrease and resulting in over-standard equipment pressure; for this reason, the following improvements have been made.

[0044] Such as Figures 5 to 8As shown, it further includes a cleaning part 10, which is arranged in the condenser 8, and the cleaning part 10 can move up and down in the condenser 8 to dredge the components in the condenser 8; it includes a first annular cavity 1001, which is opened between the outer wall of the condensation cylinder 8001 and the inner wall of the sleeve 8008 and is located in the middle of the two. A plurality of check valves are arranged at the top of the first annular cavity 1001, and the plurality of check valves are higher than the top of the collection cavity 9001 to prevent the liquid in the collection cavity 9001 from being sucked into the first annular cavity 1001 when inhaling; a first annular plate 1002, which is hermetically and slidably arranged in the first annular cavity 1001, and the first annular plate 1002 divides the first annular cavity 1001 into two parts, namely an upper cavity and a lower cavity; a second annular cavity 1003, which is opened between the outer wall of the condensation cylinder 8001 and the inner wall of the sleeve 8008 and is located at the bottom of the two; a second annular plate 1004, which is hermetically and slidably arranged in the second annular cavity 1003; a spring 1005, which is arranged in a plurality of groups and is fixedly arranged between the top of the second annular cavity 1003 and the top of the second annular plate 1004; a connecting column 1006, which is arranged in a plurality of groups and is fixedly arranged at the bottom of the first annular plate 1002, and penetrates through the first annular cavity 1001 to the second annular cavity 1003 and is fixedly arranged with the top of the second annular plate 1004, so that the first annular plate 1002 and the second annular plate 1004 move up and down synchronously; a round tube 1007, the bottom of which is embedded in the top of the condensation cylinder 8001, and the top of which is higher than the top of the condensation cylinder 8001; a nozzle 1008, which is arranged in a plurality of groups and is opened at the top of the round tube 1007, and the jet directions of the plurality of nozzles 1008 are directed towards the leakage holes 9003 to facilitate the cleaning of liquid droplets or impurities; an air flow pipe 1009, which is arranged in a plurality of groups, the tops of the plurality of air flow pipes 1009 are communicated with the bottom of the round tube 1007, and the bottoms of the plurality of air flow pipes 1009 are communicated with the bottom of the first annular cavity 1001, that is, communicated with the lower cavity of the first annular cavity 1001. An air vent pipe 1010, which is arranged in a plurality of groups and corresponds to the spiral pipe 8003, the tops of the plurality of air vent pipes 1010 are communicated with the top of the first annular cavity 1001, the bottoms of the plurality of air vent pipes 1010 are communicated with the bottoms of the corresponding spiral pipes 8003, and are located above the connection between the bottom of the spiral pipe 8003 and the air inlet hole 8005; a solenoid valve 1011, which is electrically connected to the control system, is arranged in a plurality of groups and corresponds to the spiral pipe 8003, and the solenoid valve 1011 is fixedly arranged at the bottom of the spiral pipe 8003 and is located below the air vent pipe 1010.

[0045] It should be noted that the first annular cavity 1001, the first annular plate 1002, the second annular cavity 1003 and the second annular plate 1004 are hermetically penetrated by the liquid leakage pipe 9004, and the first annular plate 1002 and the second annular plate 1004 can slide up and down hermetically along the plurality of liquid leakage pipes 9004.

[0046] In summary, when the two groups of spiral tubes 8003 are blocked, the liquid at the bottom of the tower body 12 forms steam under the action of the reboiler 7 and continuously rises. Due to the continuous rise of the steam, the gas pressure between the condenser 8 and the reboiler 7 increases. The solenoid valve 1011 closes the air inlet at the bottom of the spiral tube 8003. As the pressure continues to increase, the increased pressure pushes the first annular plate 1002 and the second annular plate 1004 upward to the first height. As Figure 8 shown, during the movement to the first height, the increased pressure pushes the second annular plate 1004 upward in the second annular cavity 1003 and compresses the spring 1005. The moving second annular plate 1004 drives the first annular plate 1002 to move synchronously in the first annular cavity 1001 through the connecting column 1006. During the movement of the first annular plate 1002, the gas in the upper cavity of the first annular cavity 1001 is squeezed. The squeezed gas enters the spiral tube 8003 through the air pipe 1010. Since the solenoid valve 1011 closes the bottom air inlet, the gas entering the spiral tube 8003 flows towards the outlet pipe 8002. During the flow of the gas, the inside of the spiral tube 8003 is dredged. When the gas dredges the spiral tube 8003, it pushes the blocked impurities in the spiral tube 8003 and pushes the impurities out through the outlet pipe 8002. The pushed-out impurities move along the inner wall arc surface of the annular cylinder 8006 and fall on the convex conical surface at the top of the condensation cylinder 8001, and then move through the leakage hole 9003 along the conical surface into the collection cavity 9001. The impurities are filtered by the filter screen 9002. The liquid droplets carried by the impurities during movement flow through the filter screen 9002 to the lower part of the filter screen 9002 and are discharged through the liquid leakage pipe 9004.

[0047] While the second annular plate 1004 drives the first annular plate 1002 to slide upward in the first annular cavity 1001 through the connecting column 1006, a negative pressure is generated in the lower cavity. Under the action of the negative pressure, the lower cavity sucks air into its interior through the nozzle 1008, the round tube 1007 and the air flow pipe 1009. The nozzle 1008 will not suck impurities into the lower cavity during the air suction process.

[0048] After the spiral tube 8003 is dredged, steam enters the air inlet hole 8005, and the solenoid valve 1011 opens the air inlet at the bottom of the spiral tube 8003. Subsequently, the steam normally flows through the spiral tube 8003, and at this time, the pressure below the condenser 8 also gradually decreases; when the pressure below the condenser 8 returns to normal, the compressed spring 1005 drives the second annular plate 1004, the connecting column 1006, and the first annular plate 1002 to return from the first height to the initial height; during the process of the first annular plate 1002 moving downward from the first height to the initial position, the first annular plate 1002 squeezes the gas in the lower cavity, causing the gas to flow through the air flow tube 1009 into the circular tube 1007 and cleaning the impurities on the convex conical surface at the top of the condensation cylinder 8001 through the gas ejected from the nozzle 1008, avoiding the influence of impurities adhering to the convex conical surface at the top of the condensation cylinder 8001 on the flow of droplets, thereby improving the flow effect of the droplets; at the same time, the gas ejected from the nozzle 1008 can also accelerate the rapid flow of the droplets at the top of the condensation cylinder 8001.

[0049] While the first annular plate 1002 moves from the first height to the initial height, the downward movement of the first annular plate 1002 creates a negative pressure in the upper cavity, opening the one-way valve, causing air to be inhaled into the upper cavity under the action of the negative pressure.

[0050] Through the cooperation of the first annular cavity 1001, the first annular plate 1002, the connecting column 1006, and the second annular plate 1004, when the air pressure below the condenser 8 increases, the solenoid valve 1011 closes the air inlet at the bottom of the spiral tube 8003. At this time, the increased pressure pushes the second annular plate 1004 upward, causing the second annular plate 1004 to drive the first annular plate 1002 to slide in the first annular cavity 1001 through the connecting column 1006 and squeeze the gas in the upper cavity. The squeezed gas enters the spiral tube 8003 through the air pipe 1010 for dredging, and the impurities inside are discharged to the top of the condensation cylinder 8001 through the air outlet pipe 8002, thereby improving the purity of product separation and realizing self-cleaning without shutting down the machine, thus improving the working efficiency.

[0051] Through the cooperation of the first annular cavity 1001, the first annular plate 1002, the connecting column 1006, the second annular plate 1004 and the spring 1005, when the spiral tube 8003 is dredged, the pressure between the condenser 8 and the reboiler 7 is restored. The compressed spring 1005 drives the second annular plate 1004 to move downward. During the downward movement of the second annular plate 1004, the first annular plate 1002 is driven by the connecting column 1006 to squeeze the gas in the lower cavity. The squeezed gas flows into the round tube 1007 through the air flow tube 1009 and is ejected through the nozzle 1008, so as to clean the impurities cleared from the spiral tube 8003 at the top of the condensation cylinder 8001, avoiding the influence on the flow of droplets due to the attachment of impurities on the protruding conical surface at the top of the condensation cylinder 8001, thereby improving the flow effect of the droplets.

[0052] Example 3, the present invention also provides a process for preparing anhydrous formic acid, which comprises the following steps:

[0053] Step 1, feeding raw materials. The raw materials react in the reaction kettle 4 to generate a mixed solution of methyl formate.

[0054] Step 2, purification. The generated mixed solution of methyl formate is purified in the gas-liquid separator 3 to obtain methyl formate.

[0055] Step 3, hydrolysis. Methyl formate is hydrolyzed in the hydrolysis reactor 2 to obtain a mixed solution containing formic acid.

[0056] Step 4, separation. Water and formic acid in the mixed solution are separated in the distillation column 1 to obtain relatively pure anhydrous formic acid.

[0057] Step 5, dehydration. The anhydrous formic acid enters the dehydration device 5 in the form of steam to remove water.

[0058] Step 6, collection. The anhydrous formic acid with water removed is collected in the product collection tank 6 to obtain the final product.

[0059] The embodiments of the present application are described above with reference to the accompanying drawings. Without conflict, the embodiments and the features in the embodiments in the present application can be combined with each other. The present application is not limited to the above specific embodiments. The above specific embodiments are only illustrative and not restrictive. Under the inspiration of the present application, those of ordinary skill in the art can also make many forms without departing from the purpose of the present application and the scope protected by the claims, all of which belong to the protection scope of the present application.

Claims

1. An anhydrous formic acid preparation device, comprising a distillation tower; A hydrolysis reactor, the top of which is connected to the bottom of the distillation tower through a pipeline; a gas-liquid separator, the bottom of which is connected to the bottom of the hydrolysis reactor through a pipeline; A reactor, the top of which is connected to the top of the gas-liquid separator through a pipeline; a dehydration device, the top of which is connected to the top of the distillation tower through a pipeline; A product collection tank, the top of which is connected to the bottom of the dehydration equipment through a pipeline; It is characterized in that The distillation tower comprises: a tower body; The reboiler is fixedly arranged at the bottom of the tower body, and the reboiler can heat the liquid at the bottom of the tower body, so that the heated liquid evaporates and turns into steam to rise; The condenser is fixedly arranged at the top of the distillation tower, and the condenser can cool the rising steam; the condenser includes: a condensation cylinder, which is arranged at the top of the tower body, and cooling water is arranged inside the condensation cylinder to cool the steam; The inner wall of the sleeve is fixedly arranged with the outer wall of the condensing cylinder, and the outer wall of the sleeve is fixedly arranged at the top of the tower body; A liquid collecting part is arranged in the top of the condenser, and can collect liquid droplets. The collected liquid droplets flow back to the reboiler through the liquid collecting part to be heated; The cleaning part is arranged in the condenser and can move up and down in the condenser to clear the components in the condenser; the cleaning part comprises: a first annular cavity, which is opened between the outer wall of the condenser tube and the inner wall of the sleeve and is located in the middle of the two; A first annular plate, which is sealingly and slidably disposed in the first annular cavity; A second annular cavity is formed between the outer wall of the condensing tube and the inner wall of the sleeve and is located at the bottom of the two; A second annular plate is sealingly and slidably disposed in the second annular cavity; The wire mesh demister is fixedly arranged at the top of the tower body and above the condenser, and can separate liquid droplets in the steam. The separated liquid droplets are collected by the liquid collecting part.

2. The anhydrous formic acid preparation device according to claim 1, characterized in that: The reboiler comprises: An annular cylinder is fixedly arranged at the bottom of the tower body; The heat exchange tubes are fixedly arranged inside the annular cylinder and can heat the liquid; A high-temperature liquid inlet is connected to one end of the heat exchange tube, and the other end of the high-temperature liquid inlet seals through the tower body and the annular cylinder and extends out of the outer wall of the tower body; A high-temperature liquid outlet is connected to one end of the heat exchange tube, and the other end of the high-temperature liquid outlet is sealed and penetrates the tower body and the annular cylinder and extends out of the outer wall of the tower body, and the high-temperature liquid outlet is in a relative position to the high-temperature liquid inlet; The first air outlet holes are provided in multiple groups and opened at the top of the annular cylinder; A heat-insulating cavity is provided inside the annular cylinder; Heating tubes are provided in multiple groups and are located between the tubes of the heat exchange tube array; The channels are provided in multiple groups and are fixedly arranged on the top of the heating tube.

3. The anhydrous formic acid preparation device according to claim 1, characterized in that: The condenser comprises: An air outlet pipe is fixedly arranged on the top of the condensation cylinder; The spiral tubes are arranged in multiple groups, and the tops of the multiple groups of spiral tubes are connected to the air outlet pipes; and the bottoms of the multiple groups of spiral tubes are fixedly arranged with the bottom of the condensation cylinder; A concave conical groove is fixedly arranged at the bottom of the condensing cylinder; The air inlet holes are arranged in groups and opened between the concave conical groove and the condensation cylinder, and the tops of the groups of air inlet holes are connected with the bottoms of the corresponding spiral tubes.

4. The anhydrous formic acid preparation device according to claim 3, characterized in that: The condenser also includes: An annular cylinder, which is fixedly arranged on the top of the condensing cylinder; The second air outlet holes are provided in multiple groups and are opened on the top of the annular cylinder, and the multiple groups of second air outlet holes are staggered with the air outlet pipe.

5. The anhydrous formic acid preparation device according to claim 4, characterized in that: The condenser also includes: A liquid inlet pipe, which is connected to one end of the condensing cylinder, and the other end of which seals and penetrates the sleeve and the tower body and extends out of the outer wall of the tower body; The liquid outlet pipe is connected to one end of the condensing cylinder, and the other end thereof seals and penetrates through the sleeve and the tower body and extends out of the outer wall of the tower body. The liquid outlet pipe is in a relative position to the liquid inlet pipe.

6. The anhydrous formic acid preparation device according to claim 5, characterized in that: The liquid collecting part also includes: A collecting chamber is provided between the outer wall of the condensing cylinder and the inner wall of the sleeve and is located at the top of the two; A filter screen is disposed in the collection chamber; The leak holes are arranged in multiple groups and are opened between the bottom of the annular cylinder and the top of the condensation cylinder; The leakage tubes are provided in multiple groups, and the tops of the multiple groups of leakage tubes are communicated with the top of the collecting chamber.

7. The anhydrous formic acid preparation device according to claim 4, characterized in that: The cleaning unit comprises: Springs are arranged in multiple groups and fixedly arranged between the top of the second annular cavity and the top of the second annular plate; The connecting columns are arranged in multiple groups and fixedly arranged at the bottom of the first annular plate.

8. The anhydrous formic acid preparation device according to claim 3, characterized in that: The cleaning unit also includes: A round tube, the bottom of which is embedded in the top of the condenser cylinder, and the top of which is higher than the top of the condenser cylinder; Nozzles are arranged in multiple groups and fixedly arranged on the top of the circular tube, and the jetting directions of the multiple groups of nozzles are toward the leakage holes; The airflow tubes are arranged in multiple groups, the tops of the multiple groups of airflow tubes are connected to the bottom of the circular tube, and the bottoms thereof are connected to the bottom of the first annular cavity.

9. The anhydrous formic acid preparation device according to claim 7, characterized in that: The cleaning unit also includes: Ventilation pipes are arranged in multiple groups and correspond to the spiral pipes, the tops of the multiple groups of ventilating pipes are connected to the tops of the first annular cavity, and the bottoms of the multiple groups of ventilating pipes are connected to the bottoms of the corresponding spiral pipes; The electromagnetic valves are arranged in multiple groups and correspond to the spiral tubes, and the electromagnetic valves are fixedly arranged at the bottom of the spiral tubes and are located below the ventilation tubes.

10. A process for preparing anhydrous formic acid, applied to the anhydrous formic acid preparation device according to claim 1, characterized in that: The following steps are involved: Step 1: adding raw materials, reacting the raw materials in a reactor to generate a methyl formate mixed solution; Step 2: Purification: purifying the generated methyl formate mixed liquid in a gas-liquid separator to obtain methyl formate; Step 3: hydrolysis, hydrolyzing methyl formate in a hydrolysis reactor to obtain a mixed solution containing formic acid; Step 4: separation, separating the water and formic acid in the mixed solution in a distillation tower to obtain relatively pure anhydrous formic acid; Step 5: Dehydration: anhydrous formic acid enters the dehydration equipment in the form of steam to remove water; Step six: collecting, collecting the anhydrous formic acid from which water has been removed into a product collection tank to obtain the final product.

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