Continuous production process and production system of paraformaldehyde

Abstract

The invention relates to the technical field of chemical production, and discloses a continuous production process and a production system of paraformaldehyde. The continuous production process of the paraformaldehyde comprises the following steps: feeding a low-concentration formaldehyde aqueous solution into a formaldehyde concentration tower for reduced-pressure flash evaporation to obtain a high-concentration formaldehyde aqueous solution; pumping the obtained high-concentration formaldehyde aqueous solution into a spray granulation tower for spray granulation to prepare a paraformaldehyde material; and feeding the obtained paraformaldehyde material into a fluidized bed dryer for fluidized drying to obtain a paraformaldehyde product. By adopting a specific combination mode of flash evaporation, spray drying and fluidized drying, the polymerization degree of the prepared paraformaldehyde product is 9-11, and the purity can reach 92-96 wt%. And in cooperation with heat preservation and flow rate control, the polymerization problem caused by too high local concentration of formaldehyde can be effectively avoided, and the continuous production mode can be well met.

Description

Technical Field

[0001] The invention relates to the field of chemical production, and in particular to a continuous production process and a production system of paraformaldehyde. Background Art

[0002] Due to its high content of effective ingredients and solid particle form, paraformaldehyde shows broad application prospects in chemical, pharmaceutical and other industrial fields.

[0003] The preparation process of paraformaldehyde includes: concentrating the formaldehyde aqueous solution, spraying and granulating the concentrated formaldehyde aqueous solution, and drying. The key to this process is to concentrate the formaldehyde aqueous solution and quickly dry the formaldehyde aqueous solution in a hot air flow by spraying and granulating to form granular paraformaldehyde.

[0004] The existing technology uses a multi-stage falling film evaporation method to concentrate the formaldehyde aqueous solution. During the falling film evaporation process, the gasification rate during heat exchange is uncontrollable, which is prone to excessive evaporation, high local formaldehyde concentration, and formaldehyde is easily aggregated into blocks, causing blockage of the equipment. The existing thin film evaporation equipment basically needs to be stopped for cleaning after running for two weeks, resulting in a large amount of energy consumption and affecting the yield. Summary of the invention

[0005] The main purpose of the present invention is to provide a continuous production process and a production system for paraformaldehyde, aiming to solve the problem that equipment is easily blocked and stopped when formaldehyde is concentrated.

[0006] To achieve the above object, the present invention provides a continuous production process of paraformaldehyde, comprising the following steps:

[0007] The low-concentration formaldehyde aqueous solution is sent to a formaldehyde concentration tower for reduced-pressure flash evaporation to obtain a high-concentration formaldehyde aqueous solution;

[0008] The obtained high-concentration formaldehyde aqueous solution is pumped into a spray granulation tower for spray granulation to obtain a paraformaldehyde material;

[0009] The obtained paraformaldehyde material is sent to a fluidized bed dryer for fluidized drying to obtain a paraformaldehyde product.

[0010] Furthermore, the concentration of the low-concentration formaldehyde aqueous solution is 15-60wt%; the concentration of the high-concentration formaldehyde aqueous solution is 70-95wt%, and more preferably 75-85wt%.

[0011] Furthermore, the concentration of the high-concentration formaldehyde aqueous solution entering the spray granulation tower can be controlled by controlling the ratio of the circulating material and the fresh low-concentration formaldehyde material in the circulation pipeline, the flow rate of the material entering the filter, and the flash pressure, temperature and other parameters.

[0012] Furthermore, when the reduced pressure flash evaporation is performed, the high-concentration formaldehyde aqueous solution coming out of the formaldehyde concentration tower is pumped to the spray granulation tower through a pipeline, and the pipeline is insulated by a heat-insulating jacket.

[0013] Furthermore, the high-concentration formaldehyde aqueous solution from the formaldehyde concentration tower is pumped to the spray granulation tower at a flow rate of 4000-6500 kg / h, and the residence time of the concentrated formaldehyde aqueous solution in the pumping pipeline from the formaldehyde concentration tower to the spray granulation tower does not exceed 5 minutes.

[0014] Preferably, the high-concentration formaldehyde aqueous solution coming out of the formaldehyde concentration tower is pumped into the spray granulation tower at a flow rate of 4000-5000 kg / h.

[0015] Furthermore, the spray granulation tower uses an atomizing spray gun to spray the concentrated formaldehyde aqueous solution, the inner diameter of the gun head of the atomizing spray gun is 20-32 mm, the diameter of the spray hole on the gun head is 0.5-2.0 mm, and / or,

[0016] The high-concentration formaldehyde aqueous solution stays in the spray granulation tower for no more than 1 minute.

[0017] Furthermore, the pressure in the atomizing spray gun is 2.0-2.8 MPa.

[0018] Furthermore, the heat source input into the spray granulation and fluidized state drying process is nitrogen.

[0019] Furthermore, the dust-containing airflow generated during the spray granulation and drying process is extracted and separated into gas and solid to form an airflow containing formaldehyde and nitrogen. The formaldehyde and nitrogen are separated, and the recovered nitrogen continues to be used as a heat source for the spray granulation and drying process.

[0020] Another object of the present invention is to provide a continuous production system of paraformaldehyde, comprising: a formaldehyde concentration tower, a spray granulation tower and a fluidized bed dryer for sequentially transmitting materials;

[0021] The formaldehyde concentration tower is provided with a circulation pipeline at the bottom and a tail gas absorption and emission section at the top;

[0022] Among them, along the circulation direction of the material, the circulation pipeline is provided with a circulation pump, a filter, a concentrated formaldehyde extraction pipeline, a formaldehyde raw material feeding pipeline, and the bottom of the formaldehyde concentration tower, and the liquid outlet end of the concentrated formaldehyde extraction pipeline is connected to the spray granulation tower.

[0023] Furthermore, a formaldehyde absorption section is arranged in the middle of the formaldehyde concentration tower.

[0024] Furthermore, the filter is arranged upstream of the concentrated formaldehyde extraction pipeline to prevent solid impurities generated during the concentration process from entering the subsequent system. Preferably, a filter with fully automatic switching and cleaning functions is used to further prevent mechanical impurities from entering the subsequent system. When the circulation volume in the circulation pipeline is large enough, switching the filter screen will not affect the subsequent process.

[0025] Furthermore, a preheater is provided in the circulation pipeline, and the fresh formaldehyde raw material and the refluxed circulating material are preheated by the preheater before entering the formaldehyde concentration tower to improve the flash evaporation efficiency.

[0026] Furthermore, the circulation pipeline, the circulation pump, the concentrated formaldehyde extraction pipeline, and the outer wall of the bottom of the formaldehyde concentration tower are provided with an insulation jacket, and the insulation jacket is insulated with hot water of 100° C. or above.

[0027] Furthermore, a pressure pump is provided on the concentrated formaldehyde extraction pipeline to increase the flow rate of the high-concentration formaldehyde aqueous solution and reduce the residence time of the high-concentration formaldehyde aqueous solution in the pipeline.

[0028] Furthermore, the granulation material outlet of the spray granulation tower is connected to the feed port of the fluidized bed dryer, and the fluidized bed dryer includes one or more drying chambers connected in series, and each drying chamber is provided with an independent material taking port.

[0029] Furthermore, the gas material outlet of the spray granulation tower and the gas material outlet of the fluidized bed dryer are both connected to cyclone separators; wherein the cyclone separator connected to the spray granulation tower is a first-stage cyclone separator, and the cyclone separator connected to the fluidized bed dryer is a second-stage cyclone separator.

[0030] Furthermore, the air inlet end of the first-stage cyclone separator is connected to the dust-containing air flow outlet of the spray granulation tower through a pipeline, and the discharge end is connected to the spray granulation tower through a pipeline so that the collected solid material is returned to the spray granulation tower, and the air outlet end is connected to the formaldehyde absorption tower.

[0031] Furthermore, the exhaust port of each drying chamber is connected to the air inlet end of the second cyclone separator through a pipeline, and the air outlet end of the second cyclone separator is connected to the formaldehyde absorption tower.

[0032] Furthermore, a bursting disc is installed in the spray granulation tower.

[0033] Furthermore, the paraformaldehyde continuous production system also includes a screening machine, and a feed port of the screening machine is connected to a discharge port of the fluidized bed dryer.

[0034] The technical solution of the present invention abandons the commonly used multi-stage film preheater to concentrate the formaldehyde aqueous solution step by step, and adopts a specific combination of flash evaporation, spray drying, and fluidized state drying, so that the polymerization degree of the obtained paraformaldehyde product is 9-11 and the purity can reach 92-96wt%. In addition, with the control of heat preservation and flow rate, the polymerization problem caused by excessively high local concentration of formaldehyde can be effectively avoided, and the continuous production mode can be better met. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0036] Figure 1 The present invention provides a schematic structural diagram of a paraformaldehyde continuous production device.

[0037] Description of Figure Numbers:

[0038] 1. Formaldehyde concentration tower; 11. Circulation pipeline; 111. Circulation pump; 112. Filter; 113. Concentrated formaldehyde extraction pipeline; 114. Formaldehyde raw material feeding pipeline; 115. Preheater; 12. Formaldehyde absorption section; 13. Tail gas absorption and emission section; 14. Insulation jacket; 2. Spray granulation tower; 21. Atomizing spray gun; 22. Gun head; 23. Bursting disc; 24. Pressure pump; 3. Fluidized bed dryer; 31. Drying chamber; 4. Screening machine; 51. First-stage cyclone separator; 52. Second-stage cyclone separator; 6. Formaldehyde absorption tower; 61. Nitrogen extraction pipe; 62. Branch pipe; 621. Heating device.

[0039] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0040] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0041] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0042] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the meaning of "and / or" appearing in the full text includes three parallel schemes. Taking "A and / or B" as an example, it includes scheme A, or scheme B, or a scheme that satisfies both A and B. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in the field to implement. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0043] The existing technology uses a multi-stage falling film evaporation method to concentrate the formaldehyde aqueous solution. During the falling film evaporation process, the gasification rate during heat exchange is uncontrollable, which is prone to excessive evaporation, high local formaldehyde concentration, and formaldehyde is easily aggregated into blocks, causing blockage of the equipment. The existing thin film evaporation equipment basically needs to be stopped for cleaning after running for two weeks, resulting in a large amount of energy consumption and affecting the yield.

[0044] In view of this, the present invention proposes a continuous production process and a production system for paraformaldehyde to solve the problem that equipment is easily blocked and stopped when formaldehyde is concentrated.

[0045] See also Figure 1 In the present invention, the paraformaldehyde continuous production system comprises: a formaldehyde concentration tower 1, a spray granulation tower 2, a fluidized bed dryer 3 and a sieving machine 4 for sequentially transmitting materials.

[0046] The formaldehyde concentration tower 1 is provided with a flash section at the bottom, a formaldehyde absorption section 12 in the middle, and a tail gas absorption and discharge section 13 at the top; the flash section includes a circulation pipeline 11, along the circulation direction of the material, the circulation pipeline 11 is provided with a circulation pump 111, a filter 112, a concentrated formaldehyde extraction pipeline 113, a formaldehyde raw material feed pipeline 114, a preheater 115, and the bottom of the formaldehyde concentration tower 1, the liquid outlet end of the concentrated formaldehyde extraction pipeline 113 is connected to the atomizing spray gun 21 at the top of the spray granulation tower 2.

[0047] By adopting the above technical scheme, the formaldehyde aqueous solution with a concentration of 15-60wt% enters the preheater 115 through the formaldehyde raw material feeding pipeline 114, and the circulating material in the circulating pipeline 11 also enters the preheater 115. The temperature of the preheated material is 50-100°C. The preheated material enters the bottom of the formaldehyde concentration tower 1, and after reduced pressure flash evaporation, the tower bottom material is a concentrated formaldehyde aqueous solution. The circulating pump 111 pumps out the tower bottom material, and after filtering through the filter 112, part of the filtered material is refluxed to the preheater 115, and the remaining part of the filtered material (formaldehyde concentration is 70-95wt%) is extracted through the concentrated formaldehyde extraction pipeline 113 and sent to the spray granulation tower 2, and the atomizing spray gun 21 sprays mist-like formaldehyde droplets, which are dried by hot air flow to form granular paraformaldehyde, and the granular paraformaldehyde is sent to the fluidized bed dryer 3, and after drying, it is sent to the screening machine 4 to screen out the paraformaldehyde with a particle size that meets the requirements. The concentrated formaldehyde extraction pipeline 113 is provided with a pressure pump 24 to increase the flow rate of the concentrated formaldehyde aqueous solution and prevent the concentrated formaldehyde from self-aggregating in the pipeline.

[0048] It should be noted that the inner diameter of the gun head 22 of the atomizing spray gun 21 is 20-32 mm, and the diameter of the spray hole on the gun head 22 is 0.5-2.0 mm.

[0049] Furthermore, the circulation pipeline 11, the circulation pump 111, the concentrated formaldehyde extraction pipeline 113, and the outer wall of the bottom of the formaldehyde concentration tower 1 are provided with an insulation jacket 14, and hot water of 100°C or above is used for insulation in the insulation jacket 14. Hot water of 100°C or above enters the insulation jacket 14 from the medium inlet of the insulation jacket 14, and after heat exchange, flows out from the medium outlet of the insulation jacket 14, and circulates in this way to keep the material in the insulation jacket warm.

[0050] Specifically, the formaldehyde absorption section 12 includes a formaldehyde side-line extraction pipe, a reflux pump, a condenser and a reflux pipe connected in sequence, the feed end of the formaldehyde side-line extraction pipe is connected to the discharge port in the middle of the formaldehyde concentration tower 1, and the liquid outlet end of the reflux pipe is connected to the return port at the top of the formaldehyde concentration tower 1. Flash gas is extracted from the formaldehyde side-line extraction pipe, and after condensation, part of the condensate is refluxed. The vacuum tail gas at the top of the tower is discharged through the tail gas absorption discharge section 13.

[0051] Furthermore, a bursting disc 23 is provided in the spray granulation tower 2; the granulation material outlet of the spray granulation tower 2 is connected to the feed port of the fluidized bed dryer 3, and the fluidized bed dryer 3 includes one or more drying chambers 31 connected in series, and each drying chamber 31 is provided with an independent material taking port. The fluidized bed dryer 3 is provided with a plurality of drying chambers 31, and a plurality of drying chambers 31 can be selected to dry the product in sequence according to production requirements. It can be understood that the heat source input and exhaust of each drying chamber 31 are independent.

[0052] Furthermore, the heat source input to the spray granulation tower 2 and each drying chamber 31 is nitrogen; the gas material outlet of the spray granulation tower 2 and the gas material outlet of the fluidized bed dryer 3 are both connected to a cyclone separator; wherein the cyclone separator connected to the spray granulation tower 2 is a first-stage cyclone separator 51, and the cyclone separator connected to the fluidized bed dryer 3 is a second-stage cyclone separator 52.

[0053] Specifically, the air inlet end of the first-stage cyclone separator 51 is connected to the dust-containing airflow outlet of the spray granulation tower 2 through a pipeline, and the discharge end is connected to the spray granulation tower 2 through a pipeline, so that the solid material collected by the first-stage cyclone separator 51 is returned to the spray granulation tower 2, and the air outlet end of the first-stage cyclone separator 51 is connected to the formaldehyde absorption tower 6; the exhaust port of each drying chamber 31 is connected to the air inlet end of the second-stage cyclone separator 52 through a pipeline, and the air outlet end of the second cyclone separator 52 is connected to the formaldehyde absorption tower 6.

[0054] By adopting the above technical scheme, the dust-containing airflow generated during the spray granulation and drying process is extracted and sent to the corresponding cyclone separator, and the cyclone separator performs gas-solid separation on the dust-containing airflow. The separated gas contains formaldehyde and nitrogen. The separated gas is sent to the formaldehyde absorption tower 6 to separate the formaldehyde and nitrogen. The nitrogen extracted from the top of the tower can be used as a heat source for spray granulation and fluidized bed drying after heating. It can also be appropriately supplemented with fresh nitrogen according to production needs. The fresh nitrogen and the recovered nitrogen are used as heat sources for spray granulation and drying after heating.

[0055] Specifically, a nitrogen extraction pipe 61 is provided at the top of the formaldehyde absorption tower 6, and the gas outlet end of the nitrogen extraction pipe 61 is respectively connected to the heat source input port of the spray granulation tower 2 and the heat source input port of each drying chamber 31, and an air pump and a fresh nitrogen input pipe are provided on the nitrogen extraction pipe 61.

[0056] By adopting the above technical solution, a plurality of branch pipes 62 are provided on the nitrogen extraction pipe 61, and the plurality of branch pipes 62 are arranged one by one corresponding to the heat source input port of the spray granulation tower 2 and the heat source input port of the plurality of drying chambers 31, and each branch pipe 62 is provided with a heating device 621. The nitrogen extracted from the top of the formaldehyde absorption tower 6 is diverted to each branch pipe 62 through the nitrogen extraction pipe 61, and then enters the corresponding spray granulation tower 2 and each drying chamber 31. It can be understood that a corresponding exhaust port is provided on the top of each drying chamber 31, and each exhaust port is connected to the air inlet end of the second-stage cyclone separator 52 through a corresponding pipeline.

[0057] The technical solution of the present invention is further described in detail below in conjunction with specific embodiments and drawings. It should be understood that the following embodiments are only used to explain the present invention and are not used to limit the present invention.

[0058] Example 1

[0059] A continuous production process of paraformaldehyde comprises the following steps:

[0060] S10. A low-concentration formaldehyde aqueous solution with a concentration of 52wt% is used as the starting raw material. The starting raw material is preheated to 80°C in a preheater and enters the flash section of the formaldehyde concentration tower. Concentrated formaldehyde and dilute formaldehyde are separated by flash evaporation under reduced pressure (vacuum degree 75kPa). The temperature of the insulation jacket of the circulation pipeline is controlled to be 100°C. When the concentration of the extracted formaldehyde reaches 80wt%, the flash evaporation circulation system is stabilized.

[0061] S20, controlling the power of the booster pump, so that the concentrated formaldehyde with a concentration of 80wt% is sent to a spray granulation tower with a single spray gun (the inner diameter of the gun head is 25mm, and the aperture of the spray hole on the gun head is 1.0mm) at a flow rate of 4500kg / h. It is calculated that the residence time of the concentrated formaldehyde in the pumping pipeline is 1min, the pressure in the spray gun is controlled to be 2.5MPa, and the temperature is 16°C. The formaldehyde aqueous solution is sprayed downward in the form of mist, and the misted formaldehyde aqueous solution is quickly dried in the hot air flow to form granular paraformaldehyde and deposited at the bottom of the tower. The paraformaldehyde at the bottom of the tower is immediately sent to the fluidized bed dryer, and the residence time of the formaldehyde aqueous solution in the spray granulation tower does not exceed 1min. The fluidized bed dryer has five drying chambers, and the drying temperature of the drying chamber is 85°C. After five stages of drying, the polyformaldehyde is sent to the screening machine to screen out the oligoformaldehyde with an average particle size of 20μm. It is measured that the polymerization degree of the oligoformaldehyde is 9-11, the purity is 92wt%, and the yield is 65% (measured as the ratio of the amount of formaldehyde in the oligoformaldehyde product to the amount of formaldehyde in the feed formaldehyde aqueous solution per unit time after the system is running stably). The equipment has been running stably for one month without any blockage or shutdown.

[0062] Example 2

[0063] A continuous production process of paraformaldehyde, which is different from Example 1 only in that the pumping speed of concentrated formaldehyde in the pumping pipeline is increased so that the residence time of concentrated formaldehyde in the pumping pipeline is 45 seconds.

[0064] The obtained paraformaldehyde has a polymerization degree of 9 to 11, a purity of 93 wt %, and a yield of 65%. The equipment ran stably for one month without any blockage or shutdown.

[0065] Example 3

[0066] A continuous production process of paraformaldehyde, which differs from Example 1 only in that the calculated residence time of concentrated formaldehyde in the pumping pipeline is 3 minutes.

[0067] The obtained paraformaldehyde has a polymerization degree of 9 to 11, a purity of 92 wt %, and a yield of 62%. The equipment operates stably for 20 days without any blockage or shutdown.

[0068] Comparative Example 1

[0069] A continuous production process of paraformaldehyde, which differs from Example 1 only in that it does not contain a heat-insulating jacket.

[0070] The obtained paraformaldehyde has a polymerization degree of 9 to 11, a purity of 89 wt % and a yield of 48%. The equipment ran stably for 15 days and then stopped due to blockage.

[0071] The above are only preferred embodiments of the present invention, and do not limit the patent scope of the present invention. For those skilled in the art, the present invention may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the patent protection scope of the present invention.

Claims

1. A continuous production process of paraformaldehyde, characterized in that: The following steps are involved: The low-concentration formaldehyde aqueous solution is sent to a formaldehyde concentration tower for reduced-pressure flash evaporation to obtain a high-concentration formaldehyde aqueous solution; The obtained high-concentration formaldehyde aqueous solution is pumped into a spray granulation tower for spray granulation to obtain a paraformaldehyde material; The obtained paraformaldehyde material is sent to a fluidized bed dryer for fluidized drying to obtain a paraformaldehyde product.

2. The continuous production process of paraformaldehyde according to claim 1, characterized in that: The high-concentration formaldehyde aqueous solution coming out of the formaldehyde concentration tower is pumped to the spray granulation tower through a pipeline, and the pipeline is insulated by a heat-insulating jacket.

3. The continuous production process of paraformaldehyde according to claim 1 or 2, characterized in that: The high-concentration formaldehyde aqueous solution from the formaldehyde concentration tower is pumped to the spray granulation tower at a flow rate of 4000-5000 kg / h, and the residence time of the high-concentration formaldehyde aqueous solution in the pumping pipeline from the formaldehyde concentration tower to the spray granulation tower does not exceed 5 minutes.

4. The continuous production process of paraformaldehyde according to claim 1, characterized in that: A high-concentration formaldehyde aqueous solution is sprayed using an atomizing spray gun, wherein the inner diameter of the gun head of the atomizing spray gun is 20 to 32 mm, and the diameter of the spray hole on the gun head is 0.5 to 2.0 mm; and / or, The concentrated formaldehyde aqueous solution stays in the spray granulation tower for no more than 1 minute.

5. A paraformaldehyde continuous production system, characterized in that: include: Formaldehyde concentration tower, spray granulation tower and fluidized bed dryer for material transmission in sequence; The formaldehyde concentration tower is provided with a circulation pipeline at the bottom and a tail gas absorption and emission section at the top; Among them, along the circulation direction of the material, the circulation pipeline is provided with a circulation pump, a filter, a concentrated formaldehyde extraction pipeline, a formaldehyde raw material feeding pipeline, and the bottom of the formaldehyde concentration tower, and the liquid outlet end of the concentrated formaldehyde extraction pipeline is connected to the spray granulation tower.

6. The continuous production system of paraformaldehyde according to claim 5, characterized in that: The circulation pipeline, the circulation pump, the concentrated formaldehyde extraction pipeline, and the outer wall of the bottom of the formaldehyde concentration tower are provided with a heat-insulating jacket.

7. The continuous production system of paraformaldehyde according to claim 5, characterized in that: The concentrated formaldehyde extraction pipeline is provided with a pressure pump to increase the flow rate of the high-concentration formaldehyde aqueous solution.

8. The paraformaldehyde continuous production system according to claim 5, characterized in that: The granulation material outlet of the spray granulation tower is connected to the feed port of the fluidized bed dryer. The fluidized bed dryer includes one or more drying chambers connected in series, and each drying chamber is provided with an independent material taking port.

9. The continuous production system of paraformaldehyde according to claim 5, characterized in that: The gas material outlet of the spray granulation tower and the gas material outlet of the fluidized bed dryer are both connected with a cyclone separator.

10. The continuous production system of paraformaldehyde according to claim 5, characterized in that: A bursting disc is installed in the spray granulation tower.

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