Formic acid concentration system and concentration method

Abstract

The present application relates to formic acid rectification concentration technical field, specifically a kind of formic acid rectification concentration system and concentration method, system includes the first rectification column, second rectification column and the first pipeline for the formic acid solution after being concentrated to the first rectification column of first rectification column, the bottom of first rectification column is connected with reboiler, the top of second rectification column is connected with second condenser, still include first condenser, two heat exchange medium passages of first condenser are respectively communicated with first rectification column and second rectification column;The present application uses first condenser to combine two towers, the heat of second rectification column is obtained by heat exchange with first rectification column, only needs to use one reboiler, saves equipment cost;First condenser simultaneously plays the role of heat exchange and condensation, does not consume additional energy, reduces the consumption of energy.

Description

Technical Field

[0001] This invention relates to the field of formic acid distillation and concentration technology, specifically to a formic acid distillation and concentration system and method. Background Technology

[0002] Currently, the most widely used method for producing formic acid is the hydrolysis of methyl formate. This process involves hydrolyzing methyl formate to obtain a mixture of formic acid, water, methanol, and methyl formate. After separating and removing methanol and methyl formate, dilute formic acid with a mass concentration of 20-60% is obtained. Because formic acid and water have extremely similar boiling points and form an azeotrope, it is impossible to obtain high-concentration formic acid using conventional distillation methods.

[0003] Patent application number 200810045043.6 discloses a method for separating and purifying high-purity formic acid from aqueous formic acid. This method uses a series of vacuum distillation and atmospheric distillation to separate formic acid and water, effectively separating the formic acid and water. However, this scheme has the following disadvantages: 1. It uses a dual-tower system (concentration tower and vacuum tower) for reaction purification, resulting in high equipment costs; 2. The heat from the water containing a small amount of formic acid separated from the concentration tower and the high-concentration formic acid solution separated from the vacuum tower cannot be recovered and utilized, resulting in heat waste. Summary of the Invention

[0004] The main objective of this invention is to provide a formic acid distillation and concentration system and method to solve the problems of high equipment cost and heat waste in the prior art.

[0005] To achieve the above objectives, the present invention provides a formic acid distillation and concentration system, comprising a first distillation column, a second distillation column, and a first pipeline for conveying the formic acid solution concentrated in the first distillation column to the second distillation column, the bottom of the first distillation column being connected to a reboiler, the top of the second distillation column being connected to a second condenser, and the system also includes a first condenser, the two heat exchange medium channels of which are respectively connected to the first distillation column and the second distillation column.

[0006] Furthermore, the second distillation column is located above the first distillation column, and the first condenser is located between the first and second distillation columns, with the first condenser connected to the top of the first distillation column and the bottom of the second distillation column.

[0007] Furthermore, a first reflux pipe is connected between the first distillation column and the second distillation column for returning the liquid from the second distillation column to the first distillation column; the first distillation column is connected to a dilute formic acid inlet pipe, and the second distillation column is connected to a concentrated formic acid outlet pipe.

[0008] Furthermore, a reflux tank is connected to the concentrated formic acid discharge pipeline, and the reflux tank is connected to the second distillation column through a third reflux pipeline.

[0009] Furthermore, one end of one heat exchange medium channel of the first condenser is connected to the first distillation column, and the other end is connected to a dilute acid water discharge pipe; one end of the other heat exchange medium channel of the first condenser is connected to the second distillation column, and the other end is connected to the first reflux pipe.

[0010] Furthermore, it also includes an inter-tower heat exchanger, a first preheater, and a second preheater; the two heat exchange medium channels of the inter-tower heat exchanger are respectively connected to the first pipeline and the first reflux pipeline; the two heat exchange medium channels of the first preheater are respectively connected to the dilute formic acid inlet pipeline and the concentrated formic acid outlet pipeline; the two heat exchange medium channels of the second preheater are respectively connected to the dilute formic acid inlet pipeline and the dilute acid water outlet pipeline.

[0011] Furthermore, a second reflux pipe is connected between the first distillation column and the dilute acid water discharge pipe.

[0012] The present invention also provides a concentration method, which uses the above-mentioned formic acid distillation and concentration system for concentration, the steps of which include: S1, dilute formic acid enters the first distillation column. The operating temperature of the first distillation column is 105-150℃, and the operating pressure is 150-450KPaG. S2. Under the thermal action of the reboiler, the water-containing gas phase rises and enters, and is condensed by the first condenser. Part of it falls into the bottom of the first distillation column, and the rest is discharged as dilute acid water along the dilute acid water discharge pipe. The bottom of the first distillation column is a formic acid solution with increased concentration. S3. The formic acid solution at the bottom of the first distillation column enters the second distillation column through the first pipeline; the operating temperature of the second distillation column is 65-95℃, and the operating pressure is 20-70 kPaA. S4. The second distillation column continues to concentrate and purify the formic acid solution. Under the thermal action inside the second distillation column, the gas phase of the formic acid solution rises to the second condenser and is condensed to form concentrated hydrochloric acid, which is discharged through the concentrated formic acid discharge pipe. The liquid phase of the formic acid solution falls to the bottom of the second distillation column and enters the first distillation column through the first reflux pipe.

[0013] Furthermore, it also includes an inter-tower heat exchanger, a first preheater, and a second preheater; the two heat exchange medium channels of the inter-tower heat exchanger are respectively connected to the first pipeline and the first reflux pipeline; the two heat exchange medium channels of the first preheater are respectively connected to the dilute formic acid inlet pipeline and the concentrated formic acid outlet pipeline; the two heat exchange medium channels of the second preheater are respectively connected to the dilute formic acid inlet pipeline and the dilute acid water outlet pipeline. In step S1, dilute formic acid is heated by exchanging heat with concentrated formic acid and dilute acid water in the first and second preheaters before entering the first distillation column. In step S3, the formic acid solution at the bottom of the first distillation column passes through the first pipe and is cooled by exchanging heat with the liquid in the first reflux pipe through the inter-column heat exchanger before entering the second distillation column.

[0014] The beneficial effects of this invention are: 1. The heat transfer from the first distillation column to the second distillation column is linked, and the pressure and temperature of the two columns must be matched. By limiting the temperature and pressure of the two columns to a specific range, it is ensured that the two columns can operate and produce a high concentration of formic acid.

[0015] 2. Existing dual-tower purification of formic acid requires each tower to be equipped with a separate reboiler. However, this invention uses a first condenser to combine the two towers. The heat of the second distillation tower is obtained by heat exchange with the first distillation tower. Only one reboiler is needed, saving equipment costs.

[0016] 3. The first condenser serves both heat exchange and condensation functions, without consuming additional energy, thus reducing energy consumption.

[0017] 4. By setting up an inter-tower heat exchanger, a first preheater, and a second preheater, the present invention can recover the heat from the liquid in the first pipe, the dilute formic acid entering the pipe, and the concentrated formic acid exiting the pipe, thus avoiding heat waste. Attached Figure Description

[0018] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0019] Figure 1 This is a schematic diagram of an embodiment of a formic acid distillation and concentration system. In the diagram: 1. First distillation column; 2. Second distillation column; 3. First pipeline; 4. First condenser; 5. First reflux pipeline; 6. Dilute formic acid inlet pipeline; 7. Concentrated formic acid outlet pipeline; 8. Inter-column heat exchanger; 9. First preheater; 10. Second preheater; 11. Dilute acid water outlet pipeline; 12. Reflux tank; 13. Reboiler; 14. Second condenser; 15. Second reflux pipeline; 16. Third reflux pipeline. Detailed Implementation

[0020] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0021] Example of a formic acid distillation and concentration system like Figure 1As shown in the embodiment of the present invention, a formic acid distillation and concentration system is provided, including a first distillation column 1 and a second distillation column 2 connected to each other, and a first pipe 3 for conveying the formic acid solution concentrated in the first distillation column 1 to the second distillation column 2. The first distillation column 1 has 15-30 theoretical plates, and the second distillation column 2 has 20-40 theoretical plates. A reboiler 13 is connected to the bottom of the first distillation column 1, and a second condenser 14 is connected to the top of the second distillation column 2. The system also includes a first condenser 4, which has two heat exchange medium channels. One end of one heat exchange medium channel is connected to the first distillation column 1, and the other end is connected to a dilute acid water discharge pipe 11. One end of the other heat exchange medium channel is connected to the second distillation column 2, and the other end is connected to a first reflux pipe 5. A delivery pump is provided on the first reflux pipe 5.

[0022] The second distillation column 2 is located above the first distillation column 1, and the first condenser 4 is located between the first distillation column 1 and the second distillation column 2. The first condenser 4 is connected to the top of the first distillation column 1 and the bottom of the second distillation column 2.

[0023] A first reflux pipe 5 is connected between the first distillation column 1 and the second distillation column 2 for returning the liquid from the second distillation column 2 to the first distillation column 1; the first distillation column 1 is connected to a dilute formic acid inlet pipe 6, and the second distillation column 2 is connected to a concentrated formic acid outlet pipe 7.

[0024] It also includes an inter-tower heat exchanger 8, a first preheater 9, and a second preheater 10. The two heat exchange medium channels of the inter-tower heat exchanger 8 are respectively connected to the first pipe 3 and the first reflux pipe 5; the two heat exchange medium channels of the first preheater 9 are respectively connected to the dilute formic acid inlet pipe 6 and the concentrated formic acid outlet pipe 7; the two heat exchange medium channels of the second preheater 10 are respectively connected to the dilute formic acid inlet pipe 6 and the dilute acid water outlet pipe 11.

[0025] A second reflux pipe 15 is connected between the first distillation column 1 and the dilute acid water discharge pipe 11. The liquid refluxed in the second reflux pipe 15 can regulate the temperature and pressure of the first distillation column 1.

[0026] A reflux tank 12 is connected to the concentrated formic acid discharge pipe 7. The reflux tank 12 is connected to the second distillation column 2 through the third reflux pipe 16. The liquid refluxed in the third reflux pipe 16 can regulate the temperature and pressure in the second distillation column 2. Both the concentrated formic acid discharge pipe 7 and the third reflux pipe 16 are equipped with transfer pumps.

[0027] Concentration Method Example 1 A concentration method, using the aforementioned formic acid distillation and concentration system, includes the following steps: S1. Dilute formic acid with a concentration of 31% is heated by exchanging heat with concentrated formic acid and dilute acid water in the first preheater 9 and the second preheater 10, and then enters the first distillation column 1. The top operating temperature of the first distillation column 1 is 135℃, the bottom operating temperature is 145℃, and the operating pressure is 200KPaG. S2. Under the thermal action of reboiler 13, the water-containing gas phase rises and enters, and is condensed by the first condenser 4. Part of it falls to the bottom of the first distillation column 1, and the rest is discharged as dilute acid water by gravity along the dilute acid water discharge pipe 11. During the discharge process, the second preheater 10 transfers heat to the dilute formic acid entering the pipe 6 through heat exchange. The bottom of the first distillation column 1 obtains a formic acid solution with a concentration of 85%. S3. The formic acid solution at the bottom of the first distillation column 1 passes through the first pipe 3 and is cooled by heat exchange with the liquid in the first reflux pipe 5 via the inter-column heat exchanger 8. It then enters the second distillation column 2. During transport, it is driven by the pressure difference between the first distillation column 1 and the second distillation column 2. The operating temperature of the top of the second distillation column 2 is 65℃, the operating temperature of the bottom of the column is 75℃, and the operating pressure is 30KPaA. S4. The second distillation column 2 continues to concentrate and purify the formic acid solution. Under the thermal action inside the second distillation column 2, the gas phase of the formic acid solution rises to the second condenser 14 and is condensed before entering the reflux tank 12. Part of it returns to the top of the second condenser 14 as reflux liquid, and the rest is discharged through the concentrated formic acid discharge pipe 7. During the discharge process, the heat is transferred to the dilute formic acid entering the pipe 6 through the first preheater 9. The concentration of the discharged concentrated formic acid is 99%. The liquid phase of the formic acid solution falls to the bottom of the second distillation column 2 and enters the first distillation column 1 through the first reflux pipe 5.

[0028] Concentration Method Example 2 A concentration method, using the aforementioned formic acid distillation and concentration system, includes the following steps: S1. Dilute formic acid with a concentration of 31% is heated by exchanging heat with concentrated formic acid and dilute acid water in the first preheater 9 and the second preheater 10, and then enters the first distillation column 1. The top operating temperature of the first distillation column 1 is 125℃, the bottom operating temperature is 133℃, and the operating pressure is 150KPaG. S2. Under the thermal action of reboiler 13, the water-containing gas phase rises and enters, and is condensed by the first condenser 4. Part of it falls to the bottom of the first distillation column 1, and the rest is discharged as dilute acid water along the dilute acid water discharge pipe 11. During the discharge process, the second preheater 10 transfers heat to the dilute formic acid entering the pipe 6 through heat exchange. The bottom of the first distillation column 1 obtains a formic acid solution with a concentration of 80%. S3. The formic acid solution at the bottom of the first distillation column 1 passes through the first pipe 3 and is cooled by heat exchange with the liquid in the first reflux pipe 5 through the inter-column heat exchanger 8. It then enters the second distillation column 2. During transport, it is driven by the pressure difference between the first distillation column 1 and the second distillation column 2. The operating temperature of the second distillation column 2 is 65℃ and the operating pressure is 20KPaA. S4. The second distillation column 2 continues to concentrate and purify the formic acid solution. Under the thermal action inside the second distillation column 2, the gas phase of the formic acid solution rises to the second condenser 14 and is condensed before entering the reflux tank 12. Part of it returns to the top of the second condenser 14 as reflux liquid, and the rest is discharged through the concentrated formic acid discharge pipe 7. During the discharge process, the heat is transferred to the dilute formic acid entering the pipe 6 through the first preheater 9. The concentration of the discharged concentrated formic acid is 99%. The liquid phase of the formic acid solution falls to the bottom of the second distillation column 2 and enters the first distillation column 1 through the first reflux pipe 5.

[0029] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A formic acid distillation and concentration system, comprising a first distillation column (1), a second distillation column (2) connected to each other, and a first pipe (3) for conveying the formic acid solution concentrated in the first distillation column (1) to the second distillation column (2), wherein a reboiler (13) is connected to the bottom of the first distillation column (1) and a second condenser (14) is connected to the top of the second distillation column (2), characterized in that, It also includes a first condenser (4), whose two heat exchange medium channels are connected to the first distillation column (1) and the second distillation column (2), respectively; A first reflux pipe (5) is connected between the first distillation column (1) and the second distillation column (2) for refluxing the liquid from the second distillation column (2) back into the first distillation column (1). One end of one heat exchange medium channel of the first condenser (4) is connected to the first distillation column (1), and the other end is connected to a dilute acid water discharge pipe (11); one end of the other heat exchange medium channel of the first condenser (4) is connected to the second distillation column (2), and the other end is connected to the first reflux pipe (5).

2. The formic acid distillation and concentration system as described in claim 1, characterized in that, The second distillation column (2) is located above the first distillation column (1), and the first condenser (4) is located between the first distillation column (1) and the second distillation column (2). The first condenser (4) is connected to the top of the first distillation column (1) and the bottom of the second distillation column (2).

3. The formic acid distillation and concentration system as described in claim 1, characterized in that, The first distillation column (1) is connected to a dilute formic acid inlet pipe (6), and the second distillation column (2) is connected to a concentrated formic acid outlet pipe (7).

4. The formic acid distillation and concentration system as described in claim 3, characterized in that, The concentrated formic acid discharge pipe (7) is connected to a reflux tank (12), and the reflux tank (12) is connected to the second distillation column (2) through a third reflux pipe (16).

5. The formic acid distillation and concentration system as described in claim 3, characterized in that, It also includes an inter-tower heat exchanger (8), a first preheater (9), and a second preheater (10); the two heat exchange medium channels of the inter-tower heat exchanger (8) are respectively connected to the first pipe (3) and the first reflux pipe (5); the two heat exchange medium channels of the first preheater (9) are respectively connected to the dilute formic acid inlet pipe (6) and the concentrated formic acid outlet pipe (7); the two heat exchange medium channels of the second preheater (10) are respectively connected to the dilute formic acid inlet pipe (6) and the dilute acid water outlet pipe (11).

6. The formic acid distillation and concentration system as described in claim 1, characterized in that, A second reflux pipe (15) is connected between the first distillation column (1) and the dilute acid water discharge pipe (11).

7. A concentration method, characterized in that, The formic acid distillation and concentration system of claim 3 is used for concentration, and the steps include: S1, dilute formic acid enters the first distillation column (1). The operating temperature of the first distillation column (1) is 105-150℃ and the operating pressure is 150-450KPaG. S2. Under the thermal action of the reboiler (13), the water-containing gas phase rises and enters, and the water-containing gas phase is condensed by the first condenser (4). Part of it falls to the bottom of the first distillation column (1), and the other part is discharged as dilute acid water along the dilute acid water discharge pipe (11). The bottom of the first distillation column (1) is a formic acid solution with increased concentration. S3. The formic acid solution at the bottom of the first distillation column (1) enters the second distillation column (2) through the first pipe (3); the operating temperature of the second distillation column (2) is 65-95℃ and the operating pressure is 20-70KPaA. S4. The second distillation column (2) continues to concentrate and purify the formic acid solution. Under the thermal action inside the second distillation column (2), the gas phase of the formic acid solution rises to the second condenser (14) and is condensed to form concentrated hydrochloric acid, which is discharged through the concentrated formic acid discharge pipe (7). The liquid phase of the formic acid solution falls to the bottom of the second distillation column (2) and enters the first distillation column (1) through the first reflux pipe (5).

8. The concentration method as described in claim 7, characterized in that, It also includes an inter-tower heat exchanger (8), a first preheater (9), and a second preheater (10); the two heat exchange medium channels of the inter-tower heat exchanger (8) are respectively connected to the first pipe (3) and the first reflux pipe (5); the two heat exchange medium channels of the first preheater (9) are respectively connected to the dilute formic acid inlet pipe (6) and the concentrated formic acid outlet pipe (7); the two heat exchange medium channels of the second preheater (10) are respectively connected to the dilute formic acid inlet pipe (6) and the dilute acid water outlet pipe (11); In step S1, dilute formic acid is heated by exchanging heat with concentrated formic acid and dilute acid water in the first preheater (9) and the second preheater (10) before entering the first distillation column (1). In step S3, the formic acid solution at the bottom of the first distillation column (1) passes through the first pipe (3) and is cooled by heat exchange with the liquid in the first reflux pipe (5) via the inter-column heat exchanger (8) before entering the second distillation column (2).

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