A device for purifying dilute formaldehyde

Abstract

The utility model discloses a dilute formaldehyde purification device, include: concentration tower, condensation evaporation heat exchanger, reflux pump group, shunt pipeline group and reflux tank, the concentration tower is equipped with middle part feed inlet, tower top distillate export, tower kettle liquid export and tower top reflux inlet, the concentration tower's middle part feed inlet is suitable for dilute formaldehyde into, the fluid inlet of condensation evaporation heat exchanger is connected with the tower top distillate export of concentration tower, the condensation evaporation heat exchanger is equipped with condensate export, the condensation evaporation heat exchanger is equipped with soft water inlet and steam export, the condensation evaporation heat exchanger is suitable for receiving the distillate of concentration tower through fluid inlet and carries out condensation, and the steam that the soft water that is introduced through soft water inlet absorbs condensation latent heat generates again, exports through steam export, the condensate export of condensation evaporation heat exchanger is connected with the reflux tank. The utility model can realize dilute formaldehyde solution concentration, and utilize latent heat that concentration tower condenses and releases simultaneously, and reduce cost and increase efficiency.

Description

Technical Field

[0001] This utility model relates to a device for purifying rare formaldehyde. Background Technology

[0002] In chemical production processes, the concentration of dilute formaldehyde solution generated in the upstream stages is typically only 10-20%. Due to its low concentration and limited added value, it cannot be directly reused in the paraformaldehyde production process. Currently, companies generally handle dilute formaldehyde solution by selling it externally or switching to the production of other low-value-added products. This not only increases sales costs, labor costs, and transportation costs but also leads to losses for the companies, making it difficult to form an effective circular industrial chain.

[0003] A search of existing technologies revealed a Chinese patent (CN109133232A) disclosing a system and method for recovering high-concentration formaldehyde solution. This technology employs a two-stage distillation process using a pressurized and a depressurized distillation tower to ultimately obtain a concentrated formaldehyde solution. While the existing technology achieves heat exchange between the formaldehyde-containing wastewater from the dilute formaldehyde storage tank and the high-temperature wastewater discharged from the pressurized tower bottom, both the overhead steam from the pressurized and depressurized towers are directly cooled by cooling water via condensers, resulting in the failure to recover and utilize the significant latent heat released during the condensation of the overhead steam. Furthermore, the system requires two distillation towers (pressurized and depressurized) to operate in series, leading to substantial equipment investment. Summary of the Invention

[0004] The technical problem to be solved by this utility model is to overcome the defects of the prior art and provide a dilute formaldehyde purification device that can concentrate dilute formaldehyde solution and at the same time utilize the latent heat released by the condensation of the concentration tower to reduce costs and increase efficiency.

[0005] To solve the above-mentioned technical problems, the technical solution of this utility model is: a dilute formaldehyde purification device, comprising:

[0006] A concentration tower is provided with a central feed inlet, a top distillate outlet, a bottom liquid outlet, and a top reflux inlet. The central feed inlet of the concentration tower is suitable for introducing dilute formaldehyde.

[0007] A condenser-evaporator heat exchanger is provided, wherein the fluid inlet of the condenser-evaporator heat exchanger is connected to the distillate outlet at the top of the concentration tower, the condenser-evaporator heat exchanger is provided with a condensate outlet, a soft water inlet and a steam outlet, and the condenser-evaporator heat exchanger is adapted to receive the distillate of the concentration tower through the fluid inlet and condense it, and absorb the latent heat of condensation to generate steam through the soft water introduced through the soft water inlet, and then output it through the steam outlet.

[0008] A reflux tank is connected to the condensate outlet of the condenser-evaporator heat exchanger, and a liquid outlet is provided at the bottom of the reflux tank.

[0009] A reflux pump unit, wherein the inlet of the reflux pump unit is connected to the liquid outlet of the reflux tank, and the reflux pump unit is provided with an outlet;

[0010] The diversion pipeline group includes a top reflux branch, a product outlet branch, and a heat exchanger reflux branch. The inlets of the top reflux branch, the product outlet branch, and the heat exchanger reflux branch are all connected to the outlet of the reflux pump group. The outlet of the top reflux branch is connected to the top reflux inlet of the concentration tower. The outlet of the heat exchanger reflux branch is connected to the condenser-evaporator heat exchanger. The outlet of the product outlet branch is suitable for outputting formaldehyde purified solution.

[0011] Furthermore, the dilute formaldehyde purification device also includes a steam switching mechanism, which is connected to the steam outlet of the condenser-evaporator heat exchanger. The steam switching mechanism is provided with an vent and a by-product steam outlet, and is adapted to switch between connecting the steam outlet and the vent and connecting the steam outlet and the by-product steam outlet according to the pressure of the condenser-evaporator heat exchanger.

[0012] Furthermore, to provide continuous heat to the bottom of the concentration tower to maintain the distillation process, the concentration tower is also equipped with a reboiler inlet;

[0013] The dilute formaldehyde purification device also includes a reboiler, the liquid inlet of which is connected to the liquid outlet of the concentrate tower, and the gas outlet of which is connected to the reboiler inlet of the concentrate tower.

[0014] Furthermore, in order to improve energy utilization efficiency and reduce energy consumption, the dilute formaldehyde purification device also includes a preheater and a dilute formaldehyde feed pipeline. The raw material inlet of the preheater is connected to the dilute formaldehyde feed pipeline, and the raw material outlet of the preheater is connected to the central feed inlet of the concentration tower.

[0015] Furthermore, a specific structure of a steam switching mechanism is provided, the steam switching mechanism including a controller, a first pressure sensor, a diversion pipeline, a first pressure regulating valve, and a second pressure regulating valve;

[0016] The inlet of the branch pipe is connected to the steam outlet of the condenser-evaporator heat exchanger, and the branch pipe is divided into a venting branch and a by-product steam branch.

[0017] The vent branch is connected to the vent outlet, and the by-product steam branch is connected to the by-product steam outlet;

[0018] The first pressure sensor is disposed on the condenser-evaporator heat exchanger, and the first pressure sensor is adapted to detect the pressure of the condenser-evaporator heat exchanger and send a first pressure signal.

[0019] The first pressure regulating valve is located on the vent branch;

[0020] The second pressure regulating valve is located on the by-product steam branch;

[0021] The controller is electrically connected to the first pressure sensor, the first pressure regulating valve, and the second pressure regulating valve, respectively. The controller is adapted to control the operation of the first pressure regulating valve and / or the second pressure regulating valve according to the first pressure signal from the first pressure sensor.

[0022] Furthermore, the dilute formaldehyde purification device also includes a second pressure sensor, a third pressure regulating valve, a fourth pressure regulating valve, and a venting pipe;

[0023] The second pressure sensor is disposed on the concentration tower, and the second pressure sensor is adapted to detect the pressure of the concentration tower and send a second pressure signal;

[0024] The third pressure regulating valve is installed on the pipeline between the distillation outlet at the top of the concentration tower and the fluid inlet of the condenser-evaporator heat exchanger.

[0025] The fourth pressure regulating valve is installed on the pipeline between the distillation outlet at the top of the concentration tower and the venting gas pipeline.

[0026] The controller is electrically connected to the second pressure sensor, the third pressure regulating valve, and the fourth pressure regulating valve, respectively. The controller is adapted to control the operation of the third pressure regulating valve and / or the fourth pressure regulating valve according to the second pressure signal from the second pressure sensor.

[0027] Furthermore, the dilute formaldehyde purification device also includes a reflux pump unit, which comprises:

[0028] A first reflux pump, the inlet of which is connected to the liquid outlet of the reflux tank;

[0029] A second reflux pump, the inlet of which is connected to the liquid outlet of the reflux tank;

[0030] The second reflux pump is connected in parallel with the first reflux pump, and the outlets of the first reflux pump and the second reflux pump are connected to the inlets of the top reflux branch, the product extraction branch, and the heat exchanger reflux branch.

[0031] Furthermore, the dilute formaldehyde purification device also includes a formaldehyde cooling heat exchanger, a circulating water supply pipe, and a circulating water return pipe.

[0032] The formaldehyde cooling heat exchanger is provided with a heat exchanger inlet, a heat exchanger outlet, a cooling medium inlet, and a cooling medium outlet.

[0033] The inlet of the formaldehyde cooling heat exchanger is connected to the outlet of the product collection branch.

[0034] The heat exchanger outlet of the formaldehyde cooling heat exchanger is suitable for conveying cooled formaldehyde purified solution.

[0035] By adopting the above technical solution, this utility model has the following beneficial effects:

[0036] In this invention, during operation, dilute formaldehyde enters the concentration tower through the middle feed inlet. The concentration tower operates under a pressure of approximately 0.4 MPa, with the temperature in the lower part controlled at approximately 152°C and the temperature at the top controlled at approximately 143°C. Under this pressure, the difference between the boiling points of water and formaldehyde increases, and the high temperature at the bottom of the tower causes both formaldehyde and water to vaporize and rise. However, during the upward movement, the temperature gradually decreases, and the water vapor first condenses and refluxes back to the lower part of the concentration tower, forming a liquid phase reflux. Meanwhile, the formaldehyde continues to accumulate in gaseous form and is discharged from the top distillation outlet into the fluid inlet of the condenser-evaporator heat exchanger. The heat exchanger uses soft water to condense formaldehyde vapor, while the soft water evaporates to produce low-pressure steam. The condensed liquid formaldehyde flows from the condensate outlet into the reflux tank. The liquid outlet at the bottom of the reflux tank is divided into three streams through a branch pipeline. The top reflux branch sends part of the formaldehyde liquid back to the top reflux inlet of the concentration tower. The product sampling branch outputs purified formaldehyde liquid as the product. The heat exchanger reflux branch sends the liquid back to the condenser-evaporator heat exchanger. The steam generated by the condenser-evaporator heat exchanger is selectively discharged from the vent or output from the by-product steam outlet for recycling as by-product steam, depending on the pressure, through a steam switching mechanism.

[0037] In summary, this invention improves the separation efficiency of formaldehyde and water, and achieves efficient energy utilization and recovery of by-product steam through the combination of a condenser-evaporator heat exchanger and a steam switching mechanism, significantly reducing energy consumption, improving economic efficiency, and showing good prospects for industrial application. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the dilute formaldehyde purification device of this utility model. Detailed Implementation

[0039] To make the contents of this utility model easier to understand, the present utility model will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0040] like Figure 1 As shown, 1. A dilute formaldehyde purification device, comprising:

[0041] Concentration tower 1 is provided with a middle feed inlet 11, a top distillate outlet 12, a bottom liquid outlet 13 and a top reflux inlet 15. The middle feed inlet 11 of concentration tower 1 is suitable for introducing dilute formaldehyde.

[0042] The condenser-evaporator heat exchanger 3 has a fluid inlet 31 connected to the top distillation outlet 12 of the concentration tower 1. The condenser-evaporator heat exchanger 3 is provided with a condensate outlet 32, a soft water inlet 33 and a steam outlet 34. The condenser-evaporator heat exchanger 3 is adapted to receive the distillate of the concentration tower 1 through the fluid inlet 31 and condense it, and absorb the latent heat of condensation by the soft water introduced through the soft water inlet 33 to generate steam, and then output it through the steam outlet 34.

[0043] Reflux tank 4 is connected to the condensate outlet 32 ​​of the condenser-evaporator heat exchanger 3, and the bottom of the reflux tank 4 is provided with a liquid outlet 41.

[0044] The reflux pump unit has its inlet connected to the liquid outlet 41 of the reflux tank 4, and the reflux pump unit is provided with an outlet.

[0045] The branch pipeline group includes a top reflux branch 42, a product outlet branch 43, and a heat exchanger reflux branch 44. The inlets of the top reflux branch 42, the product outlet branch 43, and the heat exchanger reflux branch 44 are all connected to the outlet of the reflux pump group. The outlet of the top reflux branch 42 is connected to the top reflux inlet 15 of the concentration tower 1. The outlet of the heat exchanger reflux branch 44 is connected to the condenser-evaporator heat exchanger 3. The outlet of the product outlet branch 43 is suitable for outputting formaldehyde purified liquid.

[0046] In this embodiment, as Figure 1 As shown, during operation, a dilute formaldehyde solution enters the concentration tower 1 through the middle feed inlet 11. The concentration tower 1 operates under a pressure of approximately 0.4 MPa. At a high temperature (e.g., approximately 152°C), the formaldehyde and water in the bottom of the tower vaporize and rise. At a lower temperature at the top of the tower (e.g., approximately 143°C), the higher-boiling-point water vapor is condensed and refluxed back to the lower middle section of the tower as it flows upwards, while the lower-boiling-point formaldehyde is enriched in the gas phase. The enriched formaldehyde vapor exits from the top distillation outlet 12 of the concentration tower 1 and enters the fluid inlet 31 of the condenser-evaporator heat exchanger 3.

[0047] In the condenser-evaporator heat exchanger 3, formaldehyde vapor exchanges heat with soft water (entering from soft water inlet 33) and is condensed into liquid formaldehyde. Simultaneously, the soft water evaporates to generate low-pressure steam. The condensed liquid formaldehyde distills from the condensate outlet 32 ​​and enters the reflux tank 4. The liquid outlet 41 at the bottom of the reflux tank 4 is connected to the inlet of the splitter assembly. The liquid is divided into three paths via the splitter assembly: one part is sent back to the top reflux inlet 15 of the concentration tower 1 via the top reflux branch 42; another part is output as formaldehyde purification liquid via the product collection branch 43; and the remaining part is sent back to the condenser-evaporator heat exchanger 3 via the heat exchanger reflux branch 44. The steam generated by heating the soft water is discharged from the steam outlet 34 of the condenser-evaporator heat exchanger 3 and enters the steam switching mechanism. Based on its internal pressure, the steam switching mechanism selectively discharges the steam from the vent 61 or outputs it from the by-product steam outlet 62 for recycling as by-product steam.

[0048] In addition, a first flow regulating valve and a second flow regulating valve are respectively installed on the top reflux branch 42 and the heat exchanger reflux branch 44. By adjusting the opening of the first flow regulating valve and the second flow regulating valve, the flow rate of the formaldehyde purified liquid as the product output can be controlled.

[0049] Specifically, such as Figure 1 As shown, the concentration tower 1 is also equipped with a reboiler inlet 14;

[0050] The dilute formaldehyde purification device also includes a reboiler 2, the liquid inlet 21 of which is connected to the liquid outlet 13 of the concentrate tower 1, and the gas outlet 22 of which is connected to the reboiler inlet 14 of the concentrate tower 1.

[0051] Specifically, such as Figure 1 As shown, the dilute formaldehyde purification device also includes a preheater 7 and a dilute formaldehyde feed pipeline 75. The raw material inlet of the preheater 7 is connected to the dilute formaldehyde feed pipeline 75, and the raw material outlet of the preheater 7 is connected to the central feed inlet 11 of the concentration tower 1.

[0052] In this embodiment, as Figure 1 As shown, the bottom liquid of the concentration tower 1 flows through the bottom liquid outlet 13 to the liquid inlet 21 of the reboiler 2. In the reboiler 2, the bottom liquid is heated, and the resulting mixture of gaseous formaldehyde and water vapor enters the bottom reboiler inlet 14 of the concentration tower 1 through the gas outlet 22 of the reboiler 2. This mixture rises along the trays within the concentration tower 1, contacting the liquid in the countercurrent flow, providing heat and gas phase flow to the tower.

[0053] In this embodiment, the reboiler 2 is heated by an external heat source, namely 0.6 MPa steam. This 0.6 MPa steam exchanges heat with the liquid in the reboiler 2, and the resulting post-heat exchange medium, containing residual heat, is discharged from the reboiler 2's heat exchange medium outlet. A connecting pipe is provided between the reboiler 2's heat exchange medium outlet and the preheater 7's heat medium inlet, allowing the post-heat exchange medium to enter the preheater 7. The dilute formaldehyde solution, transported by the dilute formaldehyde feed pipe 75, enters the preheater 7 from the raw material inlet and is preheated to 143°C by exchanging heat with the post-heat exchange medium. The preheated dilute formaldehyde solution is drawn from the preheater 7's raw material outlet and enters the middle section of the concentration tower 1 through the central feed inlet 11.

[0054] Specifically, such as Figure 1 As shown, the dilute formaldehyde purification device also includes a steam switching mechanism, which is connected to the steam outlet 34 of the condenser-evaporator heat exchanger 3. The steam switching mechanism is provided with an vent 61 and a by-product steam outlet 62. The steam switching mechanism is adapted to switch between connecting the steam outlet 34 with the vent 61 and connecting the steam outlet 34 with the by-product steam outlet 62 according to the pressure of the condenser-evaporator heat exchanger 3.

[0055] Specifically, such as Figure 1 As shown, the steam switching mechanism includes a controller, a first pressure sensor 64, a diversion pipeline, a first pressure regulating valve 65, and a second pressure regulating valve 66.

[0056] The inlet of the branch pipe is connected to the steam outlet 34 of the condenser-evaporator heat exchanger 3. The branch pipe is divided into a venting branch and a by-product steam branch.

[0057] The vent branch is connected to the vent outlet 61, and the by-product steam branch is connected to the by-product steam outlet 62;

[0058] The first pressure sensor 64 is disposed on the condenser-evaporator heat exchanger 3. The first pressure sensor 64 is adapted to detect the pressure of the condenser-evaporator heat exchanger 3 and send out a first pressure signal.

[0059] The first pressure regulating valve 65 is installed on the vent branch;

[0060] The second pressure regulating valve 66 is installed on the by-product steam branch;

[0061] The controller is electrically connected to the first pressure sensor 64, the first pressure regulating valve 65, and the second pressure regulating valve 66 respectively. The controller is adapted to control the operation of the first pressure regulating valve 65 and the second pressure regulating valve 66 according to the first pressure signal from the first pressure sensor 64.

[0062] In this embodiment, as Figure 1As shown, the controller can be a PLC. During operation, the first pressure sensor 64 continuously monitors the pressure inside the condenser-evaporator heat exchanger 3 and converts the detected pressure value into a first pressure signal, which is then sent to the controller. The controller receives the first pressure signal and compares it with an internally set pressure value (e.g., 0.15 MPa). When the controller determines that the pressure value corresponding to the first pressure signal has reached or exceeded the set value, the controller outputs a control signal to open the second pressure regulating valve 66 while keeping the first pressure regulating valve 65 closed. At this time, the steam outlet 34 of the condenser-evaporator heat exchanger 3 is connected to the by-product steam outlet 62 through the by-product steam branch of the branch pipeline, and the generated steam is output as by-product steam.

[0063] When the controller determines that the pressure value corresponding to the first pressure signal is lower than the set value, the controller outputs a control signal to close the second pressure regulating valve 66, thereby accumulating pressure inside the condenser-evaporator heat exchanger 3. Under certain operating conditions, such as system startup, shutdown, or when abnormal pressure requires pressure relief, the controller can control the first pressure regulating valve 65 to open, allowing steam to be discharged through the vent branch and vent port 61. In this embodiment, a make-up steam branch is also provided on the by-product steam branch. One end of this make-up steam branch is connected to the by-product steam branch, and the other end is connected to a 0.3MPa steam inlet. A make-up steam regulating valve is provided on the make-up steam branch. A third pressure sensor is also provided on the by-product steam branch, downstream of the second pressure regulating valve 66. Both the third pressure sensor and the make-up steam regulating valve are electrically connected to the aforementioned controller.

[0064] During the output of by-product steam, the third pressure sensor continuously monitors the actual pressure within the by-product steam branch. If the controller determines, based on the signal from the third pressure sensor, that the actual pressure is lower than the minimum pressure required to maintain the by-product steam, the controller outputs a signal to open the make-up steam regulating valve. At this time, make-up steam from the 0.3MPa steam inlet enters the by-product steam branch via the make-up steam branch, mixing with the existing steam, thereby causing the pressure within the by-product steam branch to rise. When the third pressure sensor detects that the pressure has returned to the set range, the controller closes the make-up steam regulating valve.

[0065] Specifically, such as Figure 1 As shown, the dilute formaldehyde purification device also includes a second pressure sensor 82, a third pressure regulating valve 83, a fourth pressure regulating valve 84, and a venting pipe 85.

[0066] The second pressure sensor 82 is disposed on the concentration tower 1. The second pressure sensor 82 is adapted to detect the pressure of the concentration tower 1 and send a second pressure signal.

[0067] The third pressure regulating valve 83 is installed on the pipeline between the distillation outlet 12 at the top of the concentration tower 1 and the fluid inlet 31 of the condenser-evaporator heat exchanger 3.

[0068] The fourth pressure regulating valve 84 is installed on the pipeline between the distillation outlet 12 at the top of the concentration tower 1 and the venting gas pipeline 85.

[0069] The controller is electrically connected to the second pressure sensor 82, the third pressure regulating valve 83 and the fourth pressure regulating valve 84 respectively. The controller is adapted to control the operation of the third pressure regulating valve 83 and / or the fourth pressure regulating valve 84 according to the second pressure signal of the second pressure sensor 82.

[0070] In this embodiment, as Figure 1 As shown, during operation, the second pressure sensor 82 detects the pressure inside the concentration tower 1 and converts the detected pressure value into a second pressure signal, which is then sent to the controller. The controller receives this second pressure signal. For example, when the second pressure sensor 82 detects that the pressure inside the concentration tower 1 exceeds a preset safety upper limit, the controller can control the third pressure regulating valve 83 to close, and simultaneously control the fourth pressure regulating valve 84 to open. The opening of the fourth pressure regulating valve 84 connects the distillate outlet 12 at the top of the concentration tower 1 with the vent pipe 85, allowing some of the steam inside the tower to be discharged through the vent pipe 85, thus rapidly reducing the pressure inside the concentration tower 1 to a safe range. Once the pressure returns to normal, the controller closes the fourth pressure regulating valve 84 and resumes normal pressure regulation via the third pressure regulating valve 83.

[0071] Specifically, such as Figure 1 As shown, the dilute formaldehyde purification device also includes a first inert gas inlet 95 and a first inert gas regulating valve 96.

[0072] The first inert gas inlet 95 and the gas outlet 22 of the reboiler 2 are both connected to the reboiler inlet 14 of the concentration tower 1.

[0073] The first inert gas regulating valve 96 is installed on the pipeline between the first inert gas inlet 95 and the reboiler inlet 14 of the concentration tower 1.

[0074] In this embodiment, as Figure 1 As shown, the first inert gas inlet 95 is used to introduce inert gas; in this embodiment, the inert gas is nitrogen. A first inert gas regulating valve 96 is located on the pipeline between the first inert gas inlet 95 and the reboiler inlet 14, and is used to control the introduction of nitrogen. Before system startup, the first inert gas regulating valve 96 can be opened to introduce nitrogen into the column to replace the air in the system and provide inert gas protection. In other embodiments, the inert gas can also be argon or other gases that do not readily react.

[0075] In addition, in this embodiment, the reflux tank 4 is also provided with an inert gas inlet (not shown in the figure). The inert gas inlet is connected to a nitrogen source and is used to introduce nitrogen into the reflux tank 4. The reflux tank 4 is also provided with a connecting pipe connected to the vent pipe 85 and a control valve installed on the corresponding connecting pipe.

[0076] Specifically, such as Figure 1 As shown, the dilute formaldehyde purification device also includes a reflux pump unit, which includes:

[0077] The inlet of the first reflux pump 101 is connected to the liquid outlet 41 of the reflux tank 4;

[0078] The inlet of the second reflux pump 102 is connected to the liquid outlet 41 of the reflux tank 4;

[0079] The second reflux pump 102 is connected in parallel with the first reflux pump 101. The outlet of the first reflux pump 101 and the outlet of the second reflux pump 102 are connected to the inlet of the top reflux branch 42, the product extraction branch 43 and the heat exchanger reflux branch 44.

[0080] In this embodiment, as Figure 1 As shown, under normal operating conditions, the controller can start the first reflux pump 101 to pressurize the liquid in the reflux tank 4 and send it out, while the second reflux pump 102 is in a stopped standby state.

[0081] To facilitate isolation and maintenance of either reflux pump, valves are installed on the inlet and outlet pipes of the first reflux pump 101, and valves are also installed on the inlet and outlet pipes of the second reflux pump 102. For example, when the first reflux pump 101 needs maintenance, its inlet and outlet valves can be closed, and the second reflux pump 102 will then undertake all liquid transport tasks. In some embodiments, the use is not limited to only the first reflux pump 101 and the second reflux pump 102; multiple reflux pumps can be used.

[0082] Specifically, such as Figure 1 As shown, the dilute formaldehyde purification device also includes a formaldehyde cooling heat exchanger 121, a circulating water supply pipe, and a circulating water return pipe.

[0083] The formaldehyde cooling heat exchanger 121 is provided with a heat exchanger inlet, a heat exchanger outlet, a cooling medium inlet, and a cooling medium outlet;

[0084] The inlet of the formaldehyde cooling heat exchanger 121 is connected to the outlet of the product outlet branch 43.

[0085] The heat exchanger outlet of formaldehyde cooling heat exchanger 121 is suitable for conveying cooled formaldehyde purified liquid.

[0086] In this embodiment, as Figure 1 As shown, the formaldehyde purified liquid drawn from the outlet of product extraction branch 43, due to its high temperature, is transported to the inlet of the formaldehyde cooling heat exchanger 121. The high-temperature formaldehyde purified liquid flows within the formaldehyde cooling heat exchanger 121. Simultaneously, the cooling medium (circulating water in this embodiment) is transported to the cooling medium inlet of the formaldehyde cooling heat exchanger 121 through the circulating water supply pipe and flows within the heat exchanger, exchanging heat with the formaldehyde purified liquid. The formaldehyde purified liquid transfers its heat to the circulating water and is cooled. The circulating water, heated after absorbing heat, is discharged from the cooling medium outlet and flows away through the circulating water return pipe. The cooled formaldehyde purified liquid is then drawn from the outlet of the formaldehyde cooling heat exchanger 121 for subsequent storage and transportation.

[0087] The working principle of this invention is as follows: During the startup phase, the first inert gas regulating valve 96 is opened, and nitrogen gas is introduced into the concentration tower 1 and reflux tank 4 through the first inert gas inlet 95 to replace the air in the concentration tower 1 and form an inert gas protective atmosphere. Subsequently, the reboiler 2 is started, and the initial liquid in the bottom of the concentration tower 1 is heated using an external heat source (such as 0.6MPa steam). At this time, since the heat exchange cycle has not yet been established, the first batch of dilute formaldehyde solution fed from the dilute formaldehyde feed pipe 75 cannot be effectively preheated when it enters the preheater 7, but instead enters the concentration tower 1 at a lower temperature from the middle feed inlet 11. As the reboiler 2 continues to heat, the internal temperature of the concentration tower 1 gradually increases, and a gas-liquid two-phase system begins to form and circulate inside the tower, gradually approaching the set operating temperature (approximately 152°C at the bottom and approximately 143°C at the top) and pressure (approximately 0.4MPa).

[0088] Once the system reaches a stable operating state, the heat-exchange medium discharged from reboiler 2, retaining residual heat, is transported to preheater 7 to preheat the subsequently entering dilute formaldehyde solution, bringing it to approximately 143°C before it enters concentration tower 1, thereby reducing the energy consumption of the concentration tower. Inside concentration tower 1, formaldehyde and water achieve efficient separation under pressure due to the increased difference in boiling points. Water vapor condenses and refluxes within the tower, while the enriched formaldehyde vapor is discharged from the top distillation outlet 12.

[0089] The discharged formaldehyde vapor enters the condenser-evaporator heat exchanger 3, where it is condensed into liquid formaldehyde, while simultaneously heating the soft water into low-pressure steam. The liquid formaldehyde flows into the reflux tank 4, is drawn out by the reflux pump group, and is distributed through the branch pipeline group: part of it returns to the top of the concentration tower 1 via the tower top reflux branch 42; part of it returns to the condenser-evaporator heat exchanger 3 via the heat exchanger reflux branch 44; and the remaining part is sent to the formaldehyde cooling heat exchanger 121 for cooling via the product collection branch 43, and then output as the final product.

[0090] The specific embodiments described above further illustrate the technical problems, technical solutions, and beneficial effects of this utility model. It should be understood that the above descriptions are merely specific embodiments of this utility model and are not intended to limit this utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. A dilute formaldehyde purification apparatus, characterized by comprising: include: Concentration tower (1), the concentration tower (1) is provided with a central feed inlet (11), a top distillate outlet (12), a bottom liquid outlet (13) and a top reflux inlet (15), the central feed inlet (11) of the concentration tower (1) is suitable for introducing dilute formaldehyde; A condenser-evaporator heat exchanger (3) is provided. The fluid inlet (31) of the condenser-evaporator heat exchanger (3) is connected to the top distillation outlet (12) of the concentration tower (1). The condenser-evaporator heat exchanger (3) is provided with a condensate outlet (32). The condenser-evaporator heat exchanger (3) is provided with a soft water inlet (33) and a steam outlet (34). The condenser-evaporator heat exchanger (3) is adapted to receive the distillate of the concentration tower (1) through the fluid inlet (31) and condense it. The soft water introduced through the soft water inlet (33) absorbs the latent heat of condensation to generate steam, and then outputs it through the steam outlet (34). A reflux tank (4) is connected to the condensate outlet (32) of the condenser-evaporator heat exchanger (3), and a liquid outlet (41) is provided at the bottom of the reflux tank (4). A reflux pump assembly, the inlet of which is connected to the liquid outlet (41) of the reflux tank (4), and the reflux pump assembly is provided with an outlet; The diversion pipeline group includes a top reflux branch (42), a product outlet branch (43), and a heat exchanger reflux branch (44). The inlets of the top reflux branch (42), the product outlet branch (43), and the heat exchanger reflux branch (44) are all connected to the outlet of the reflux pump group. The outlet of the top reflux branch (42) is connected to the top reflux inlet (15) of the concentration tower (1). The outlet of the heat exchanger reflux branch (44) is connected to the condenser-evaporator heat exchanger (3). The outlet of the product outlet branch (43) is suitable for outputting formaldehyde purified liquid.

2. The dilute formaldehyde purification device according to claim 1, characterized in that: It also includes a steam switching mechanism, which is connected to the steam outlet (34) of the condenser-evaporator heat exchanger (3). The steam switching mechanism is provided with an vent (61) and a by-product steam outlet (62). The steam switching mechanism is adapted to switch between the connection between the steam outlet (34) and the vent (61) and the connection between the steam outlet (34) and the by-product steam outlet (62) according to the pressure of the condenser-evaporator heat exchanger (3).

3. The dilute formaldehyde purification device according to claim 2, characterized in that: The steam switching mechanism includes a controller, a first pressure sensor (64), a diversion pipeline, a first pressure regulating valve (65), and a second pressure regulating valve (66). The inlet of the branch pipe is connected to the steam outlet (34) of the condenser-evaporator heat exchanger (3), and the branch pipe is divided into an venting branch and a by-product steam branch; The vent branch is connected to the vent (61), and the by-product steam branch is connected to the by-product steam outlet (62); The first pressure sensor (64) is disposed on the condenser-evaporator heat exchanger (3), and the first pressure sensor (64) is adapted to detect the pressure of the condenser-evaporator heat exchanger (3) and send out a first pressure signal; The first pressure regulating valve (65) is located on the vent branch; The second pressure regulating valve (66) is installed on the by-product steam branch; The controller is connected to the first pressure sensor (64), the first pressure regulating valve (65), and the second pressure regulating valve (66) respectively. The controller is adapted to control the first pressure regulating valve (65) and / or the second pressure regulating valve (66) to operate according to the first pressure signal of the first pressure sensor (64).

4. The dilute formaldehyde purification device according to claim 1, characterized in that: The concentration tower (1) is also provided with a reboiler inlet (14). It also includes a reboiler (2), the liquid inlet (21) of which is connected to the liquid outlet (13) of the bottom of the concentration tower (1), and the gas outlet (22) of which is connected to the reboiler inlet (14) of the bottom of the concentration tower (1).

5. The dilute formaldehyde purification device according to claim 4, characterized in that: It also includes a preheater (7) and a dilute formaldehyde feed line (75), the raw material inlet of the preheater (7) is connected to the dilute formaldehyde feed line (75), and the raw material outlet of the preheater (7) is connected to the central feed inlet (11) of the concentration tower (1).

6. The dilute formaldehyde purification device according to claim 3, characterized in that: It also includes a second pressure sensor (82), a third pressure regulating valve (83), a fourth pressure regulating valve (84), and a venting pipe (85); The second pressure sensor (82) is disposed on the concentration tower (1), and the second pressure sensor (82) is adapted to detect the pressure of the concentration tower (1) and emit a second pressure signal; The third pressure regulating valve (83) is installed on the pipeline between the top distillation outlet (12) of the concentration tower (1) and the fluid inlet (31) of the condenser-evaporator heat exchanger (3); The fourth pressure regulating valve (84) is installed on the pipeline between the top distillation outlet (12) of the concentration tower (1) and the venting gas pipeline (85); The controller is connected to the second pressure sensor (82), the third pressure regulating valve (83) and the fourth pressure regulating valve (84) respectively. The controller is adapted to control the operation of the third pressure regulating valve (83) and / or the fourth pressure regulating valve (84) according to the second pressure signal of the second pressure sensor (82).

7. The dilute formaldehyde purification device according to claim 1, characterized in that: The reflux pump assembly includes: The inlet of the first reflux pump (101) is connected to the liquid outlet (41) of the reflux tank (4); The inlet of the second reflux pump (102) is connected to the liquid outlet (41) of the reflux tank (4); The second reflux pump (102) is connected in parallel with the first reflux pump (101), and the outlet of the first reflux pump (101) and the outlet of the second reflux pump (102) are connected to the inlet of the top reflux branch (42), the product extraction branch (43), and the heat exchanger reflux branch (44).

8. The dilute formaldehyde purification device according to claim 1, characterized in that: It also includes a formaldehyde cooling heat exchanger (121), a circulating water supply pipe and a circulating water return pipe; The formaldehyde cooling heat exchanger (121) is provided with a heat exchanger inlet, a heat exchanger outlet, a cooling medium inlet, and a cooling medium outlet; The inlet of the formaldehyde cooling heat exchanger (121) is connected to the outlet of the product outlet branch (43). The heat exchanger outlet of the formaldehyde cooling heat exchanger (121) is suitable for conveying the cooled formaldehyde purified liquid.

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