Formic acid rectification concentration system and process

Abstract

The present application relates to formic acid rectification concentration technical field, especially to a kind of formic acid rectification concentration system and process.The formic acid rectification concentration system includes azeotropic dehydration tower and azeotropic agent separation tower, the azeotropic dehydration tower is connected with low concentration formic acid inlet and azeotropic agent inlet, the azeotropic dehydration tower top is connected with layered tank, the azeotropic dehydration tower top and the layered tank between are connected with first condenser, the azeotropic dehydration tower bottom is connected with first reboiler, the azeotropic dehydration tower bottom is connected with azeotropic agent separation tower by pipeline, the azeotropic agent separation tower top is connected with second condenser, the azeotropic agent separation tower bottom is connected with second reboiler.The present application is concentrated using azeotropic rectification process to realize formic acid aqueous solution, using 1,2-dichloroethane as azeotropic agent, formic acid yield is high, can simultaneously reduce equipment material requirement, and reduce the formic acid content in separated water, can prepare anhydrous formic acid, no by-product generation.

Description

Technical Field

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

[0002] Formic acid is an important chemical raw material. Large quantities of low-concentration formic acid solutions are generated during the production of pharmaceuticals and fragrances, as well as the acid treatment of textiles and leather, but these solutions have no practical application. Recovering and concentrating this low-concentration formic acid (w% > 85%) can reduce environmental pollution and create considerable economic value. Because formic acid and water have extremely similar boiling points and can form an azeotrope, high-concentration formic acid cannot be obtained using conventional distillation methods.

[0003] Currently, the main methods for recovering formic acid include azeotropic distillation, pressure swing distillation, and dehydration with desiccants.

[0004] Azeotropic distillation yields good results and is suitable for industrial applications. When treating low-concentration formic acid solutions, conventional distillation can be used first to remove water, yielding a formic acid solution with an approximate azeotropic composition. Then, an azeotropic agent is added to separate the water. The key to this method is selecting a suitable azeotropic agent. It must not decompose during use, have strong water-carrying capacity, and ideally, the azeotropic agent should not azeotropically react with formic acid, or the azeotropic temperature between the azeotropic agent and formic acid should be significantly different from that between the azeotropic agent and water, facilitating separation.

[0005] Pressure swing distillation (PSD) achieves formic acid dehydration and concentration by altering the formic acid-water azeotropic ratio through changing the distillation operating pressure. A method using a series of pressurized distillations to separate formic acid and water employs acid-resistant metal distillation columns, resulting in high equipment costs. Furthermore, the required theoretical plate number and reflux ratio for separating formic acid and water lead to high energy consumption. Additionally, the separated water still contains a certain amount of formic acid, resulting in a low formic acid yield that necessitates alkali neutralization, further increasing the wastewater treatment load.

[0006] The desiccant dehydration method is suitable for concentrating formic acid aqueous solutions with low water content. However, this process generates solid waste and has high treatment costs. Summary of the Invention

[0007] In view of the shortcomings of the prior art, the purpose of this invention is to provide a formic acid distillation and concentration system and process.

[0008] To achieve the above objectives, the technical solution adopted is:

[0009] One objective of this invention is to provide a formic acid distillation and concentration system, comprising an azeotropic dehydration tower and an azeotropic agent separation tower. The azeotropic dehydration tower is connected to a low-concentration formic acid inlet and an azeotropic agent inlet. A layering tank is connected to the top of the azeotropic dehydration tower. A first condenser is connected between the top of the azeotropic dehydration tower and the layering tank. A first reboiler is connected to the bottom of the azeotropic dehydration tower. The bottom of the azeotropic dehydration tower is connected to the azeotropic agent separation tower via a pipeline. A second condenser is connected to the top of the azeotropic agent separation tower, and a second reboiler is connected to the bottom of the azeotropic agent separation tower.

[0010] Furthermore, the bottom of the azeotropic dehydration tower is connected to the middle of the azeotropic agent separation tower via a second outflow pipe.

[0011] Furthermore, the layered tank contains an upper aqueous phase and a lower oil phase. The upper aqueous phase is connected to a water storage tank and an azeotropic dehydration tower, respectively, and the lower oil phase is connected to the azeotropic dehydration tower.

[0012] Furthermore, the upper aqueous phase is connected to a water storage tank via a first extraction pipe, and to an azeotropic dehydration tower via a second return pipe and a first return pipe.

[0013] Furthermore, the second condenser is connected to a receiving tank, which is connected to the azeotropic agent separation tower.

[0014] Furthermore, the second condenser is connected to the top of the azeotropic agent separation tower via a third reflux pipe and to a receiving tank via a third outflow pipe. A first transfer pump is connected to the outlet pipe of the receiving tank, and the first transfer pump is connected to a raw material tank via a return pipe.

[0015] Furthermore, the bottom of the azeotropic separator is connected to a formic acid product storage tank.

[0016] Furthermore, the bottom of the azeotropic separator is connected to the formic acid product storage tank via a fourth outflow pipe.

[0017] Furthermore, both the first condenser and the second condenser are connected to a cooling water inlet and a cooling water outlet.

[0018] Furthermore, both the first and second condensers are connected to exhaust gas outlets.

[0019] Furthermore, both the first and second reboilers are connected to a low-pressure steam inlet and a condensate outlet.

[0020] Furthermore, the formic acid distillation and concentration system also includes an azeotropic agent treatment device.

[0021] The beneficial effect of adopting the above-mentioned further technical solution is that: an azeotropic agent treatment device is provided on the first extraction pipeline, which can be a distillation column or a kettle. Since the aqueous phase separated by the azeotropic dehydration column does not contain formic acid, but will contain a small amount of azeotropic agent dichloroethane, the dichloroethane in the aqueous phase needs to be distilled off through the distillation column or kettle and then enters the water storage tank.

[0022] The second objective of this invention is to provide a formic acid distillation and concentration process, which uses the aforementioned formic acid distillation and concentration system for concentration, and includes the following steps:

[0023] Low-concentration formic acid and the azeotropic agent dichloroethane are fed into the azeotropic dehydration tower through the low-concentration formic acid inlet and the azeotropic agent inlet, respectively. Under atmospheric pressure heating conditions, a mixture of dichloroethane and water is distilled off and cooled in the first condenser. The resulting first condensate flows by gravity to the separation tank, where it is allowed to settle and separate. The lower oil phase after separation is mainly dichloroethane and returns to the azeotropic dehydration tower along the pipeline. The upper aqueous phase is mainly water and is divided into two parts: one part of the upper aqueous phase is collected to the water storage tank, and the other part of the upper aqueous phase is returned to the azeotropic dehydration tower. The azeotropic dehydration tower is heated by the first reboiler. A formic acid-dichloroethane-water mixture with a water content of less than 10% is collected from the bottom of the tower and transferred to the azeotropic agent separation tower through the pipeline.

[0024] Under normal pressure heating conditions, the azeotropic agent separation tower distills off the remaining dichloromethane, which, along with some water and formic acid, is condensed and cooled in the second condenser. Part of the resulting second condensate is returned to the top of the azeotropic agent separation tower E, while the other part is collected and sent to the receiving tank, and then returned to the raw material tank for secondary processing. The azeotropic agent separation tower is heated through the second reboiler, and the formic acid product without azeotropic agent is collected from the bottom of the tower and transferred to the formic acid product storage tank.

[0025] The beneficial effect of adopting the above technical solution is that the process designed in this invention must ensure that the reflux liquid at the top of the azeotropic dehydration tower contains not only the lower oil phase after separation, but also a part of the upper aqueous phase; otherwise, the upper aqueous phase solution after separation will contain formic acid.

[0026] Furthermore, the formic acid distillation and concentration process includes the following specific steps:

[0027] Low-concentration formic acid and the azeotropic agent dichloroethane are fed into the azeotropic dehydration tower through the low-concentration formic acid inlet and the azeotropic agent inlet, respectively. Under atmospheric pressure heating conditions, a mixture of dichloroethane and water is distilled off and cooled in the first condenser. The resulting first condensate flows by gravity to a separation tank, where it is allowed to settle and separate. The lower oil phase after separation is mainly dichloroethane and returns to the azeotropic dehydration tower along the first reflux pipe. The upper aqueous phase is mainly water. A portion of the upper aqueous phase is collected to a water storage tank through the first extraction pipe, and another portion is returned to the azeotropic dehydration tower through the second reflux pipe, also via the first reflux pipe. The azeotropic dehydration tower is heated by the first reboiler. A formic acid-dichloroethane-water mixture with a water content of less than 10% is collected from the bottom of the tower and transferred to the azeotropic agent separation tower through the second extraction pipe.

[0028] Under atmospheric pressure heating conditions, the azeotropic agent separation tower distills off the remaining dichloromethane, which, along with some water and formic acid, is condensed and cooled in the second condenser. Part of the resulting second condensate is returned to the top of the azeotropic agent separation tower as reflux liquid through the third reflux pipeline, while the other part is collected to the receiving tank through the third collection pipeline and then returned to the raw material tank for secondary processing via the first transfer pump along the return pipeline. The raw material tank is actually the storage tank for the material to be processed. The material to be processed needs to be transferred to the azeotropic dehydration tower for azeotropic dehydration. In the azeotropic agent separation tower, the azeotropic agent-formic acid-water fraction collected in the early stage cannot be used as a qualified product or as an azeotropic agent. This fraction cannot be discarded and needs to be returned to the raw material tank to be mixed with the raw material and then transferred to the azeotropic dehydration tower for processing. The azeotropic agent separation tower is heated by the second reboiler, and the formic acid product without azeotropic agent is collected from the bottom of the tower and transferred to the formic acid product storage tank along the fourth collection pipeline.

[0029] Furthermore, the bottom temperature of the azeotropic dehydration tower is 80℃~90℃, and the top temperature is 75℃~80℃.

[0030] Furthermore, the bottom temperature of the azeotropic agent separation tower is 95℃~105℃, and the top temperature is 80℃~100℃.

[0031] Furthermore, the formic acid distillation and concentration process also includes the following step: adding formic anhydride to the formic acid product to obtain anhydrous formic acid.

[0032] The beneficial effects of adopting the above-mentioned further technical solutions are as follows: In the process designed by the present invention, the water content of the formic acid product collected from the bottom of the azeotropic agent separation tower can be controlled within 3%. If anhydrous formic acid is to be produced, formic anhydride can be added to the product, and formic acid can be generated by the reaction of formic anhydride with water to achieve the preparation of anhydrous formic acid.

[0033] Compared with existing technologies, the advantages of this invention are as follows: This invention uses an azeotropic distillation process to concentrate formic acid aqueous solution, employing 1,2-dichloroethane as the azeotropic agent. This azeotropic agent has a strong water-carrying capacity, and its azeotropic temperature with water is relatively low, at 65°C. This azeotropic temperature differs significantly from the azeotropic temperature of dichloroethane-formic acid (76.7°C), resulting in minimal formic acid loss and a high formic acid yield during the azeotropic dehydration process. This process can simultaneously reduce the requirements for equipment materials and decrease the formic acid content in the separated water. To prepare anhydrous formic acid, after dehydrating the formic acid solution to less than 5% water content through azeotropic distillation, formic anhydride is directly added. The formic anhydride reacts with water to generate formic acid, thereby achieving the preparation of anhydrous formic acid.

[0034] Meanwhile, the material requirements for the equipment can be reduced, and conventional non-metallic equipment such as enamel / graphite can meet the requirements. Since the azeotropic temperature of dichloroethane and water and the azeotropic temperature of dichloroethane-formic acid are quite different, the water separated during the azeotropic dehydration process contains almost no formic acid. After simple evaporation to remove the azeotropic agent, it can be directly discharged, reducing the pressure on wastewater treatment. Formic acid can be concentrated to a content greater than 97%. If anhydrous formic acid is to be prepared, formic anhydride can be added after the azeotropic distillation dehydration is completed, which consumes the remaining water and generates formic acid without the generation of by-products. Attached Figure Description

[0035] Figure 1 This is a flowchart of a formic acid distillation and concentration system and process according to the present invention;

[0036] The attached diagram is labeled as follows: A, Azeotropic Dehydration Tower; B, First Condenser; C, Separation Tank; D, First Reboiler; E, Azeotropic Agent Separation Tower; F, Second Condenser; G, Receiving Tank; H, First Transfer Pump; J, Second Reboiler; 1, Low-Concentration Formic Acid Inlet; 2, Azeotropic Agent Inlet; 3, First Condensate; 4, Second Reflux Pipeline; 5, Lower Oil Phase; 6, First Production Pipeline; 7, First Reflux Pipeline; 8, Second Production Pipeline; 9, Second Condensate; 10, Third Reflux Pipeline; 11, Third Production Pipeline; 12, Return Pipeline; 13, Fourth Production Pipeline; 14, Cooling Water Inlet; 15, Cooling Water Outlet; 16, Low-Pressure Steam Inlet; 17, Condensate Outlet; 18, Exhaust Gas Outlet. Detailed Implementation

[0037] The present invention will be described below with reference to examples. These examples are only used to explain the present invention and are not intended to limit the scope of the present invention.

[0038] Reference Figure 1A formic acid distillation and concentration system includes an azeotropic dehydration tower A and an azeotropic agent separation tower E. The azeotropic dehydration tower A is connected to a low-concentration formic acid inlet 1 and an azeotropic agent inlet 2. A layering tank C is connected to the top of the azeotropic dehydration tower A. A first condenser B is connected between the top of the azeotropic dehydration tower A and the layering tank C. A first reboiler D is connected to the bottom of the azeotropic dehydration tower A. The bottom of the azeotropic dehydration tower A is connected to the azeotropic agent separation tower E through a pipeline. A second condenser F is connected to the top of the azeotropic agent separation tower E. A second reboiler J is connected to the bottom of the azeotropic agent separation tower E.

[0039] In this embodiment, the bottom of the azeotropic dehydration tower A is connected to the middle of the azeotropic agent separation tower E through the second outflow pipe 8.

[0040] In a preferred embodiment, the layered tank C contains an upper aqueous phase and a lower oil phase 5. The upper aqueous phase is connected to a water storage tank and an azeotropic dehydration tower A, respectively, and the lower oil phase 5 is connected to the azeotropic dehydration tower A.

[0041] In this embodiment, the upper aqueous phase is connected to the water storage tank through the first extraction pipe 6, and is connected to the azeotropic dehydration tower A through the second return pipe 4 and the first return pipe 7.

[0042] In this embodiment, the second condenser F is connected to a receiving tank G, which is connected to the azeotropic agent separation tower E.

[0043] In a preferred embodiment, the second condenser F is connected to the top of the azeotropic agent separation tower E through the third reflux pipe 10, and is connected to the receiving tank G through the third outflow pipe 11. The outlet pipe of the receiving tank G is connected to the first transfer pump H, and the first transfer pump H is connected to the raw material tank through the return pipe 12.

[0044] In an optional embodiment, the bottom of the azeotropic separator E is connected to a formic acid product storage tank.

[0045] In this embodiment, the bottom of the azeotropic separator E is connected to the formic acid product storage tank via the fourth outflow pipe 13.

[0046] In this embodiment, both the first condenser B and the second condenser F are connected to a cooling water inlet 14 and a cooling water outlet 15.

[0047] In a preferred embodiment, both the first condenser B and the second condenser F are connected to an exhaust gas outlet 18.

[0048] In this embodiment, both the first reboiler D and the second reboiler J are connected to a low-pressure steam inlet 16 and a condensate outlet 17.

[0049] In this embodiment, both the bottom of the azeotropic dehydration tower A and the azeotropic agent separation tower E are connected to a transfer pump.

[0050] In this embodiment, the formic acid distillation and concentration system further includes an azeotropic agent treatment device.

[0051] This invention also provides a formic acid distillation and concentration process, comprising the following specific steps: low-concentration formic acid and azeotropic agent dichloroethane are introduced into azeotropic dehydration tower A through low-concentration formic acid inlet 1 and azeotropic agent inlet 2, respectively. Under atmospheric pressure heating conditions, a mixture of dichloroethane and water is distilled off and cooled in the first condenser B. The resulting first condensate 3 flows by gravity to the layering tank C and is allowed to stand and separate into layers. The lower oil phase 5 after separation is mainly dichloroethane and returns to azeotropic dehydration tower A along the first reflux pipe 7. The upper aqueous phase is mainly water and is divided into two parts. One part of the upper aqueous phase is collected to a water storage tank through the first collection pipe 6, and the other part of the upper aqueous phase is returned to azeotropic dehydration tower A through the second reflux pipe 4 and the first reflux pipe 7. Azeotropic dehydration tower A is heated by the first reboiler D. A formic acid-dichloroethane-water mixture with a water content of less than 10% is collected from the bottom of the tower and transferred to the azeotropic agent separation tower E through the second collection pipe 8 under the drive of the transfer pump.

[0052] Under atmospheric pressure heating conditions, the azeotropic agent separation tower E distills off the remaining dichloromethane, which, along with some water and formic acid, is condensed and cooled in the second condenser F. Part of the resulting second condensate 9 is returned to the top of the azeotropic agent separation tower E as reflux liquid through the third reflux pipe 10, and part is collected to the receiving tank G through the third collection pipe 11, and then returned to the raw material tank for secondary processing via the first transfer pump H along the return pipeline 12. The azeotropic agent separation tower E is heated by the second reboiler J, and the formic acid product without azeotropic agent is collected from the bottom of the tower. Driven by the transfer pump, it is transferred to the formic acid product storage tank along the fourth collection pipe 13.

[0053] In a preferred embodiment, the bottom temperature of the azeotropic dehydration tower A is 80℃~90℃, and the top temperature is 75℃~80℃.

[0054] In a preferred embodiment, the bottom temperature of the azeotropic agent separation tower E is 95℃~105℃, and the top temperature is 80℃~100℃.

[0055] In an optional embodiment, the formic acid distillation and concentration process further includes the following step: adding formic anhydride to the formic acid product to obtain anhydrous formic acid.

[0056] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A formic acid distillation and concentration system, characterized in that, The system includes an azeotropic dehydration tower and an azeotropic agent separation tower. The azeotropic dehydration tower is connected to a low-concentration formic acid inlet and an azeotropic agent inlet. A layering tank is connected to the top of the azeotropic dehydration tower. A first condenser is connected between the top of the azeotropic dehydration tower and the layering tank. A first reboiler is connected to the bottom of the azeotropic dehydration tower. The bottom of the azeotropic dehydration tower is connected to the azeotropic agent separation tower via a pipeline. A second condenser is connected to the top of the azeotropic agent separation tower. A second reboiler is connected to the bottom of the azeotropic agent separation tower. The layering tank contains an upper aqueous phase and a lower oil phase. The upper aqueous phase is connected to a water storage tank and the azeotropic dehydration tower, respectively. The lower oil phase is connected to the azeotropic dehydration tower.

2. The formic acid distillation and concentration system according to claim 1, characterized in that, The second condenser is connected to a receiving tank, which is connected to the azeotropic agent separation tower.

3. The formic acid distillation and concentration system according to claim 1, characterized in that, The bottom of the azeotropic separator is connected to a formic acid product storage tank.

4. A formic acid distillation and concentration process, characterized in that, The formic acid distillation and concentration system as described in any one of claims 1 to 3 is used for concentration, and the steps include: Low-concentration formic acid and the azeotropic agent dichloroethane are fed into the azeotropic dehydration tower through the low-concentration formic acid inlet and the azeotropic agent inlet, respectively. Under atmospheric pressure heating conditions, a mixture of dichloroethane and water is distilled off and cooled in the first condenser. The resulting first condensate flows by gravity to the separation tank, where it is allowed to settle and separate. The lower oil phase after separation is mainly dichloroethane and is returned to the azeotropic dehydration tower via a pipeline. The upper aqueous phase is mainly water. Part of the upper aqueous phase is collected to a water storage tank, and the other part is returned to the azeotropic dehydration tower. The azeotropic dehydration tower is heated through the first reboiler. A formic acid-dichloroethane-water mixture with a water content of less than 10% is collected from the bottom of the tower and transferred to the azeotropic agent separation tower via a pipeline. Under atmospheric pressure heating conditions, the azeotropic agent separation tower distills off the remaining dichloromethane, which, along with some water and formic acid, is condensed and cooled in the second condenser. Part of the resulting second condensate is returned to the top of the azeotropic agent separation tower, while the other part is collected and sent to a receiving tank, and then returned to the raw material tank for secondary processing. The azeotropic agent separation tower is heated through a second reboiler, and the bottom of the tower yields formic acid product without azeotropic agent, which is then transferred to the formic acid product storage tank.

5. The formic acid distillation and concentration process according to claim 4, characterized in that, The bottom temperature of the azeotropic dehydration tower is 80℃~90℃, and the top temperature is 75℃~80℃.

6. The formic acid distillation and concentration process according to claim 4, characterized in that, The bottom temperature of the azeotropic agent separation tower is 95℃~105℃, and the top temperature is 80℃~100℃.

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