Formaldehyde-containing gas-phase material condensation treatment device for polyoxymethylene dimethyl ether separation process

Abstract

The utility model discloses a condensation treatment device for a formaldehyde-containing gas-phase material, and belongs to the technical field of chemical production equipment. The device comprises a first heat exchanger and a buffer tank, a hot side inlet of the first heat exchanger is connected with a formaldehyde-containing gas phase material input pipeline, and a hot side outlet of the first heat exchanger is connected with an inlet of the buffer tank through a condensed material output pipeline; a cold-side inlet of the first heat exchanger is connected with a cold-side medium input pipeline, and a cold-side outlet of the first heat exchanger is connected with a vaporizing medium output pipeline; the bottom of the buffer tank is connected with the liquid-phase material output pipeline, and the top of the buffer tank is connected with the gas-phase material output pipeline. The utility model provides a simple and reliable condensation treatment device for a formaldehyde-containing gas phase material in a polyoxymethylene dimethyl ether separation process, and the device effectively solves the problem that the condensation equipment is easy to polymerize in the polyoxymethylene dimethyl ether product separation process, and ensures the production continuity of the device.

Description

Technical Field

[0001] The utility model belongs to the technical field of chemical production equipment, and specifically relates to a condensation treatment device for formaldehyde-containing gas phase materials in a polyoxymethylene dimethyl ether separation process. Background Art

[0002] Polyoxymethylene dimethyl ether is a type of acetal compound with methyleneoxy as the main chain and methyl and methoxy as the end groups. Its general structural formula is CH3O(CH2O) n CH3, where n is the number of methyleneoxy units, and polyoxymethylene dimethyl ether with n methyleneoxy units is referred to as Mn. Polyoxymethylene dimethyl ether has excellent solubility and low toxicity. When mixed with other conventional solvents, it can be widely used in many fields such as metal cleaning, adhesive preparation, printing and dyeing auxiliary preparation, and paint and coating thinner preparation.

[0003] The reaction for synthesizing polyoxymethylene dimethyl ether is a reversible equilibrium process. The reaction liquid mixture flowing out of the reactor generally contains a large amount of unconverted formaldehyde. Generally, a product with a certain degree of polymerization needs to be obtained through multi-stage distillation. However, in the distillation separation process of the polyoxymethylene dimethyl ether reaction liquid mixture or the polyoxymethylene dimethyl ether product mixture containing formaldehyde, formaldehyde, as a light component with a low boiling point, is easily enriched in the evaporated gas phase material. When these gas phase materials are condensed by a conventional industrial condenser using circulating cooling water as the cold side medium, formaldehyde is easily polymerized on the heat exchange surface of the condenser to generate solid formaldehyde polymers, causing a decrease in heat transfer efficiency, which seriously endangers the long-term stable operation of the separation equipment. In addition, when a conventional industrial condenser using circulating cooling water as the cold side medium is used to condense the gas phase material containing formaldehyde, a large amount of condensation latent heat of the material is not utilized, which is not conducive to reducing the energy consumption and cost of product production. Utility Model Content

[0004] Based on the above technical problems, the utility model proposes a condensation treatment device for formaldehyde-containing gaseous materials used in the polyoxymethylene dimethyl ether separation process.

[0005] The technical solution adopted by this utility model is:

[0006] A formaldehyde-containing gaseous material condensation processing device used in a polyoxymethylene dimethyl ether separation process comprises a first heat exchanger and a buffer tank, wherein the hot side inlet of the first heat exchanger is connected to a formaldehyde-containing gaseous material input pipeline, and the hot side outlet of the first heat exchanger is connected to an inlet of the buffer tank through a condensed material output pipeline;

[0007] The cold side inlet of the first heat exchanger is connected to the cold side medium input pipeline, and the cold side outlet of the first heat exchanger is connected to the vaporized medium output pipeline;

[0008] The bottom of the buffer tank is connected to the liquid material output pipeline, and the top of the buffer tank is connected to the gaseous material output pipeline;

[0009] A first pressure regulating valve is arranged on the vaporized medium output pipeline, and a second pressure regulating valve is arranged on the gas phase material output pipeline; a cold side medium feed regulating valve is arranged on the cold side medium input pipeline, and a buffer tank liquid level regulating valve is arranged on the liquid phase material output pipeline.

[0010] Preferably, a condensate pump is provided on the liquid material output pipeline.

[0011] Preferably, a first pressure sensor and a first liquid level sensor are provided on the cold side of the first heat exchanger, the first pressure sensor is connected to the first pressure regulating valve, and the first liquid level sensor is connected to the cold side medium feed regulating valve;

[0012] A second pressure sensor and a second liquid level sensor are arranged on the buffer tank. The second pressure sensor is connected to the second pressure regulating valve, and the second liquid level sensor is connected to the buffer tank liquid level regulating valve.

[0013] Preferably, the vaporized medium output pipeline is connected to the hot side inlet of the second heat exchanger, the hot side outlet of the second heat exchanger is connected to the cold side medium input pipeline through the cold side medium circulation pipeline, and a circulation pump is arranged on the cold side medium circulation pipeline; the cold side inlet of the second heat exchanger is connected to the cooling water input pipeline, and the cold side outlet of the second heat exchanger is connected to the cooling water output pipeline.

[0014] Preferably, the gas phase material output pipeline is connected to the bottom gas inlet of the water scrubber, and the top gas outlet of the water scrubber is connected to the incinerator through the tail gas delivery pipeline.

[0015] Preferably, the first heat exchanger is a kettle heat exchanger or a thermosyphon heat exchanger.

[0016] The beneficial technical effects of the utility model are:

[0017] The utility model provides a simple and reliable condensation treatment device for formaldehyde-containing gas phase materials in the polyoxymethylene dimethyl ether separation process through in-depth research on the polyoxymethylene dimethyl ether product separation process and formaldehyde characteristics.

[0018] The utility model has wide adaptability to the condensation of formaldehyde-containing gaseous intermediate materials or formaldehyde-containing gaseous polyoxymethylene dimethyl ether products in the process of polyoxymethylene dimethyl ether synthesis or separation. In this device, the solubility of formaldehyde in the condensed liquid phase material is relatively small, and part of the formaldehyde is separated from the liquid phase main material in the form of non-condensable gas and discharged from the system. By heat exchange with the cold side medium, the vaporization temperature of the cold side medium of the first heat exchanger can be accurately controlled to avoid the occurrence of formaldehyde polymerization reaction, which not only ensures the continuity of the device production and reduces the formaldehyde loss, but also the cold side medium can be used as feed for other separation or reaction equipment after vaporization, thereby recovering the heat of the formaldehyde-containing gas phase material and reducing the energy consumption of the separation process.

[0019] The utility model not only has remarkable effects of energy saving and consumption reduction, but also improves the continuity of device production and has strong industrial practicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The utility model is further described below in conjunction with the accompanying drawings and specific embodiments:

[0021] Figure 1 This is a schematic diagram of the structural principle of the first embodiment of the utility model;

[0022] Figure 2 This is a schematic diagram of the structural principle of the second embodiment of the utility model;

[0023] Figure 3 This is a schematic diagram of the structural principle of the third embodiment of the utility model;

[0024] Figure 4 This is a schematic diagram of the structural principle of the fourth embodiment of the utility model.

[0025] In the figure: 1-first heat exchanger, 2-buffer tank, 3-formaldehyde-containing gas-phase material input pipeline, 4-condensed material output pipeline, 5-cold side medium input pipeline, 6-vaporized medium output pipeline, 7-liquid phase material output pipeline, 8-gas phase material output pipeline, 9-first pressure regulating valve, 10-second pressure regulating valve, 11-cold side medium feed regulating valve, 12-buffer tank liquid level regulating valve, 13-condensate pump, 14-first pressure sensor, 15-first liquid level sensor, 16-second pressure sensor, 17-second liquid level sensor, 18-evaporation tank, 19-second heat exchanger, 20-circulation pump, 21-cooling water input pipeline, 22-cooling water output pipeline, 23-water washing tower, 24-exhaust gas delivery pipeline, 25-spray liquid input pipeline, 26-washing liquid output pipeline. DETAILED DESCRIPTION

[0026] The following embodiments are only used to illustrate the present invention and are not intended to limit the scope of application of the present invention. After reading the present invention, various equivalent modifications made by technicians in the relevant fields according to the essential principles of the present invention are all within the scope defined by the claims described in this application.

[0027] Example 1

[0028] like Figure 1 As shown, a condensation treatment device for formaldehyde-containing gaseous materials in a polyoxymethylene dimethyl ether separation process comprises a first heat exchanger 1 and a buffer tank 2, wherein the first heat exchanger 1 is a kettle-type heat exchanger. The hot side inlet of the first heat exchanger 1 is connected to a formaldehyde-containing gaseous material input pipeline 3, and the hot side outlet of the first heat exchanger 1 is connected to the inlet of the buffer tank 2 through a condensed material output pipeline 4. The cold side inlet of the first heat exchanger 1 is connected to a cold side medium input pipeline 5, and the cold side outlet of the first heat exchanger 1 is connected to a vaporized medium output pipeline 6. The bottom of the buffer tank 2 is connected to a liquid material output pipeline 7, and the top of the buffer tank 2 is connected to a gaseous material output pipeline 8.

[0029] A first pressure regulating valve 9 is provided on the vaporized medium output pipeline 6, and a second pressure regulating valve 10 is provided on the gas phase material output pipeline 8. A cold side medium feed regulating valve 11 is provided on the cold side medium input pipeline 5, and a buffer tank liquid level regulating valve 12 is provided on the liquid phase material output pipeline 7. A condensate pump 13 is provided on the liquid phase material output pipeline 7.

[0030] A first pressure sensor 14 and a first liquid level sensor 15 are provided on the cold side of the first heat exchanger 1. The first pressure sensor 14 is connected to the first pressure regulating valve 9, and the first liquid level sensor 15 is connected to the cold side medium feed regulating valve 11. A second pressure sensor 16 and a second liquid level sensor 17 are provided on the buffer tank 2. The second pressure sensor 16 is connected to the second pressure regulating valve 10, and the second liquid level sensor 17 is connected to the buffer tank liquid level regulating valve 12.

[0031] The first pressure sensor 14 cooperates with the first pressure regulating valve 9 to adjust the vaporization pressure on the cold side of the first heat exchanger. The second pressure sensor 16 cooperates with the second pressure regulating valve 10 to adjust the condensation pressure on the hot side of the first heat exchanger. The first liquid level sensor 15 cooperates with the feed regulating valve 11 to adjust the feed amount of the medium on the cold side of the first heat exchanger. The second liquid level sensor 17 cooperates with the buffer tank liquid level regulating valve 12 to adjust the liquid level of the buffer tank 2.

[0032] The working process of the utility model is roughly as follows:

[0033] The first heat exchanger 1 adopts a kettle heat exchanger. The gaseous intermediate material containing formaldehyde or the gaseous polyoxymethylene ether product containing formaldehyde in the process of polyoxymethylene ether synthesis or separation enters the hot side of the first heat exchanger 1 through the formaldehyde-containing gaseous material input pipeline 3 for condensation. One or more of methanol, methylal, polyoxymethylene ether M2, or methanol aqueous solution as the cold side medium enters the cold side of the first heat exchanger 1 through the cold side medium input pipeline 5 for vaporization. After the formaldehyde-containing gaseous material is condensed, it enters the buffer tank 2 through the condensed material output pipeline 4 for vapor-liquid separation. The hot side condensation pressure regulating valve of the first heat exchanger, i.e., the second pressure regulating valve 10, is adjusted to control the condensation pressure of the hot side of the first heat exchanger 1, so that the saturation temperature of the formaldehyde-containing gaseous material at the inlet of the first heat exchanger 1 is greater than 105°C. The gaseous material at the top of the buffer tank 2 enters the downstream supporting tail gas treatment facilities through the gaseous material output pipeline 8 to purify or recover the formaldehyde and other organic components therein. The liquid material at the bottom of the buffer tank 2 is sent out by the condensate pump 13 through the liquid material output pipeline 7 and used as the reflux of the distillation tower or the feed of other equipment. The liquid level of the buffer tank 2 is controlled by adjusting the buffer tank liquid level regulating valve 12. The cold side medium is vaporized on the cold side of the first heat exchanger 1, and the cold side vaporization pressure regulating valve, i.e., the first pressure regulating valve 9, is adjusted to control the vaporization pressure on the cold side of the first heat exchanger 1, so that the vaporization temperature of the cold side medium on the cold side of the first heat exchanger 1 is not less than 90°C. At the same time, the temperature of the condensate in the condensed material output pipeline 4 at the hot side outlet of the first heat exchanger 1 is not less than 100°C. After the cold side medium is vaporized, it is sent out through the vaporized medium output pipeline 6 and used as the feed of other separation equipment or reaction equipment, indirectly recovering the heat released by the condensation of the formaldehyde-containing gas phase material and reducing the overall energy consumption of the separation process.

[0034] Example 2

[0035] Based on the structure of Example 1, the following specific designs are also performed:

[0036] like Figure 2 As shown, the vaporized medium output pipeline 6 is connected to the hot side inlet of the second heat exchanger 19, and the hot side outlet of the second heat exchanger 19 is connected to the cold side medium input pipeline 5 through the cold side medium circulation pipeline, and a circulation pump 20 is provided on the cold side medium circulation pipeline. The cold side inlet of the second heat exchanger 19 is connected to the cooling water input pipeline 21, and the cold side outlet of the second heat exchanger 19 is connected to the cooling water output pipeline 22. The second heat exchanger 19 can adopt a conventional industrial condenser.

[0037] The second heat exchanger 19 in this embodiment uses conventional circulating cooling water as the cold side medium to condense the methanol, methylal and other media vaporized in the first heat exchanger 1. The cold side medium vaporized in the first heat exchanger 1 is condensed into liquid in the second heat exchanger and then circulated back to the first heat exchanger 1 for recycling. The cold side medium feed regulating valve 11 is adjusted to control the shell side liquid level of the kettle heat exchanger.

[0038] Example 3

[0039] Based on the structure of Example 1, the following specific designs are also performed:

[0040] like Figure 3 As shown, the gas phase material output pipeline 8 is connected to the bottom gas inlet of the water scrubber 23, and the top gas outlet of the water scrubber is connected to the incinerator through the tail gas delivery pipeline 24. The upper part of the water scrubber 23 is also connected to the spray liquid input pipeline 25, and the bottom of the water scrubber 23 is connected to the washing liquid output pipeline 26. The gas phase material discharged from the buffer tank 2 enters the water scrubber 23, contacts with the spray liquid in countercurrent, absorbs and condenses to recover most of the formaldehyde and polyoxymethylene dimethyl ether components, and then the remaining tail gas is discharged through the tail gas delivery pipeline 24, which can be further sent to the incinerator for incineration.

[0041] Example 4

[0042] like Figure 4 As shown, the basic structure is the same as that of embodiment 1, except that: the first heat exchanger 1 is a thermosyphon heat exchanger. The thermosyphon heat exchanger is vertical or horizontal, and is equipped with a distillation tower kettle or an evaporation tank.

[0043] When a vertical thermosyphon or horizontal thermosyphon heat exchanger is used, the cold side medium completes the siphon cycle and vapor-liquid separation between the first heat exchanger and the matching evaporator 18. The cold side medium vaporizes on the cold side of the first heat exchanger 1, and the first pressure regulating valve 9 controls the pressure of the distillation tower kettle or the evaporator, indirectly controlling the cold side vaporization pressure of the first heat exchanger 1. The cold side medium feed regulating valve 11 of the first heat exchanger is adjusted to control the liquid level of the distillation tower kettle or the evaporator.

[0044] The utility model is further described below in conjunction with specific application examples:

[0045] This embodiment provides a condensation treatment process of formaldehyde-containing gas-phase polyoxyethylene dimethyl ether M2.

[0046] The aldehyde-containing M was separated by distillation tower. 2-8 The mixture contains about 0.16% formaldehyde by mass, about 62.2% M2 by mass, and about 0.16% formaldehyde by mass. 3-8 The mass content is about 37.5%, and the rest is trace methylal, methanol and water. The M2 fraction is taken out from the top of the distillation tower, and the remaining M 3-8 The mixture is extracted from the bottom of the distillation tower. The distillation tower has an inner diameter of 25mm and a height of 3m. It is filled with two sections of Φ3mmθ mesh ring random packing. The height of a single section of packing is 1m. A liquid level meter and an electric heater are installed at the bottom of the tower. The gas phase material at the top of the distillation tower is connected to the following through a well-insulated stainless steel pipe: Figure 1The first heat exchanger 1 is shown as a small U-shaped tube kettle heat exchanger. The gaseous material enters the buffer tank 2 after condensation in the first heat exchanger 1. A temperature measuring point is provided on the formaldehyde-containing gaseous material input pipeline 3. A second pressure regulating valve 10 is provided on the gaseous material output pipeline 8 at the top of the buffer tank 2 to control the pressure in the buffer tank. The outlet of the gaseous material output pipeline 7 is connected to the bubbling absorption bottle. Part of the liquid phase material in the buffer tank is sent back to the top of the distillation tower by the reflux pump for reflux, and part is extracted as the top fraction. The shell side of the first heat exchanger 1 is provided with a pressure gauge, a liquid level gauge and a temperature measuring point. The first pressure regulating valve 9 arranged on the vaporized medium output pipe 6 at the top can control the pressure of the shell side of the first heat exchanger 1. The outlet of the vaporized medium output pipe 6 is connected to a three-necked flask. The vaporized cold side medium can be condensed into liquid through the spherical condenser above the three-necked flask, and then transported to the shell side of the first heat exchanger 1 through the cold side medium input pipe 5 by the metering pump for recycling. The spherical condenser uses room temperature tap water as the cooling medium.

[0047] A proper amount of crude methylal is filled in the three-necked flask and the first shell side of the first heat exchanger as the cold side circulation medium. The methylal liquid level in the first shell side of the first heat exchanger is such that the U-shaped condenser bundle can be immersed. The crude methylal contains about 10% methanol by mass and a trace amount of water. A metering pump is used to pump the above liquid phase containing aldehyde M at a speed of 20 ml / min. 2-8The mixture is continuously sent to the feed port in the middle of the distillation tower as feed. After the appropriate liquid level is established at the bottom of the distillation tower, the bottom heating is used to establish total reflux for the distillation tower. The gaseous material is condensed in the U-shaped tube of the first heat exchanger. The crude methylal in the shell side of the first heat exchanger is heated and vaporized. The first pressure regulating valve 9 is adjusted to control the pressure of the shell side of the first heat exchanger 1 to be about 0.37-0.44MPaG, so that the shell side temperature of the first heat exchanger 1 is maintained at 90-95°C. The vaporized crude methylal steam enters the condensation facility through the vaporization medium output pipeline 6 to be condensed into liquid crude methylal and collected in a three-necked flask, and then is pumped out by the metering pump and transported to the shell side of the first heat exchanger 1 through the cold side medium input pipeline 5 for recycling. The flow rate of the crude methylal transported by the metering pump to the shell side of the first heat exchanger is adjusted to maintain the liquid level of the shell side of the first heat exchanger to immerse the U-shaped tube bundle. The heating capacity at the bottom of the distillation tower and the second pressure regulating valve 10 are adjusted to control the pressure in the buffer tank 2 and the pressure at the top of the distillation tower to reach 45-50 KPaG, so that the temperature at the top of the distillation tower reaches about 115-118°C. After the buffer tank 2 establishes a suitable liquid level, the reflux pump is started to reflux the condensate to the top of the distillation tower, and the reflux flow rate is gradually increased to 20 ml / min. After the reflux is established, the bottom heating of the distillation tower and the top discharge flow rate are gradually adjusted to make the M2 component in the feed be extracted from the top of the distillation tower. After the operation is stable, the temperature of the temperature measuring point on the formaldehyde-containing gas phase material input pipeline 3 is about 108-110°C, the bottom temperature of the distillation tower is about 175-178°C, and the top M2 discharge flow rate is about 13.5-14 ml / min. The top and bottom discharges are taken regularly to analyze the full composition. The formaldehyde content in the top M2 liquid phase fraction is about 0.2% by mass, and the M2 content is about 99.6% by mass. The rest is trace methylal, methanol, water and M3 components. 3-8 The formaldehyde content of the mixture is about 0.004%, the M2 content is about 0.5%, and the rest is M 3-8 Component.

[0048] The distillation separation was continued for 24 hours under the above conditions. After the separation was completed, the U-shaped tube bundle of the first heat exchanger 1 was opened for inspection, and no signs of formaldehyde polymerization were found, indicating that the device of the utility model can achieve safe and stable condensation of formaldehyde-containing gaseous materials in the first heat exchanger.

Claims

1. A condensation treatment device for formaldehyde-containing gaseous materials used in a polyoxymethylene dimethyl ether separation process, characterized in that: It comprises a first heat exchanger and a buffer tank, wherein the hot side inlet of the first heat exchanger is connected to a formaldehyde-containing gas phase material input pipeline, and the hot side outlet of the first heat exchanger is connected to the inlet of the buffer tank through a condensed material output pipeline; The cold side inlet of the first heat exchanger is connected to the cold side medium input pipeline, and the cold side outlet of the first heat exchanger is connected to the vaporized medium output pipeline; The bottom of the buffer tank is connected to the liquid material output pipeline, and the top of the buffer tank is connected to the gaseous material output pipeline; A first pressure regulating valve is arranged on the vaporized medium output pipeline, and a second pressure regulating valve is arranged on the gas phase material output pipeline; a cold side medium feed regulating valve is arranged on the cold side medium input pipeline, and a buffer tank liquid level regulating valve is arranged on the liquid phase material output pipeline.

2. The formaldehyde-containing gas phase material condensation treatment device used in the polyoxymethylene dimethyl ether separation process according to claim 1, characterized in that: A condensate pump is provided on the liquid material output pipeline.

3. The formaldehyde-containing gas phase material condensation treatment device used in the polyoxymethylene dimethyl ether separation process according to claim 1, characterized in that: A first pressure sensor and a first liquid level sensor are arranged on the cold side of the first heat exchanger, the first pressure sensor is connected to the first pressure regulating valve, and the first liquid level sensor is connected to the cold side medium feed regulating valve; A second pressure sensor and a second liquid level sensor are arranged on the buffer tank. The second pressure sensor is connected to the second pressure regulating valve, and the second liquid level sensor is connected to the buffer tank liquid level regulating valve.

4. The formaldehyde-containing gas phase material condensation treatment device used in the polyoxymethylene dimethyl ether separation process according to claim 1, characterized in that: The vaporized medium output pipeline is connected to the hot side inlet of the second heat exchanger, and the hot side outlet of the second heat exchanger is connected to the cold side medium input pipeline through the cold side medium circulation pipeline, and a circulation pump is arranged on the cold side medium circulation pipeline; the cold side inlet of the second heat exchanger is connected to the cooling water input pipeline, and the cold side outlet of the second heat exchanger is connected to the cooling water output pipeline.

5. The formaldehyde-containing gas phase material condensation treatment device used in the polyoxymethylene dimethyl ether separation process according to claim 1, characterized in that: The gas phase material output pipeline is connected to the bottom gas inlet of the water washing tower, and the top gas outlet of the water washing tower is connected to the incinerator through the tail gas delivery pipeline.

6. The formaldehyde-containing gas phase material condensation treatment device used in the polyoxymethylene dimethyl ether separation process according to claim 1, characterized in that: The first heat exchanger is a kettle heat exchanger or a thermosyphon heat exchanger.

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