System for producing polyformaldehyde

Abstract

The utility model discloses a system for producing polyformaldehyde, and belongs to the technical field of polymer production. According to the continuous flow synthesis device disclosed by the utility model, formaldehyde, trioxymethylene, dioxopenta (penta) ring and polyformaldehyde are prepared into a continuous flow synthesis device through a plurality of different synthesis units, materials in each stage can be conveyed to the next stage through simple operation in the production process, and meanwhile, unreacted or waste materials in a system can be recycled; and the recycled materials enter the previous stage to be continuously utilized, so that the waste of the materials is avoided, and the energy consumption during subsequent waste treatment is also saved.

Description

TECHNICAL FIELD

[0001] The utility model relates to the technical field of polymer production, specifically relates to a system for producing polyformaldehyde. BACKGROUND

[0002] Polyformaldehyde is a kind of linear polymer material with high density and high crystallinity, and its regular molecular structure and high crystallinity make it have very excellent physical and mechanical properties. The mechanical properties of polyformaldehyde are closest to metal among engineering plastics, and it has good dimensional stability, resistance to water, oil and chemicals, and excellent wear resistance. It is a kind of thermoplastic resin with excellent comprehensive performance, and has high elastic modulus, hardness, rigidity and mechanical properties in a relatively large temperature range. It can replace metal materials such as steel, copper, zinc and aluminum in many occasions, and is widely used in mechanical industry, light industry, electronics, automobile industry and agricultural equipment fields, and is known as "metal in plastic".

[0003] Polyformaldehyde can be divided into homopolyformaldehyde and copolyformaldehyde according to the different chemical structures in its molecular chain. Homopolyformaldehyde has high density, crystallinity and melting point, but poor thermal stability, narrow processing temperature range (about 10 DEG C) and slightly lower acid and alkali stability. Copolyformaldehyde has lower density, crystallinity, melting point and strength than homopolyformaldehyde due to the C-C structure in its main chain, but has excellent thermal stability, is not easy to decompose, has wide processing temperature range (50 DEG C), good acid and alkali stability and easy molding processing. Therefore, copolyformaldehyde is more widely used in practical applications, especially in fields requiring high thermal stability and good processing performance.

[0004] The synthesis process of copolyformaldehyde usually copolymerizes trioxymethylene and dioxolane, wherein trioxymethylene is prepared by concentrating, purifying and rectifying formaldehyde, trioxymethylene and a small amount of dioxolane are subjected to ring-opening polymerization to form copolymerization monomer linkage to form a high molecular chain, and then copolyformaldehyde is refined by rectification and purification. For example, patent CN111848889B discloses a method for preparing polyformaldehyde by coproduction of trioxymethylene and dioxolane. Hemiacetal is synthesized by using ethylene glycol and formaldehyde in trioxymethylene crude product, and is separated for synthesizing dioxolane. Trioxymethylene monomer and dioxolane monomer are used for polymerization reaction to prepare polyformaldehyde. In the technical scheme, impurity ions in the synthesis process are not easy to remove, the purity of the prepared material is low, and the operation is complex.

[0005] In summary, copolyformaldehyde is widely studied because its processing process is easy to control, and it is usually prepared by copolymerizing trioxymethylene and dioxolane. However, the preparation process of copolyformaldehyde has low formaldehyde utilization rate, serious pollution in synthesis process, easy waste of raw materials, low yield of copolyformaldehyde and long preparation time, which are still problems to be solved. UTILITY MODEL CONTENT

[0006] The utility model provides a system of producing polyformaldehyde, the system includes formaldehyde synthesis unit, trioxymethylene synthesis unit, dioxolane (pentolane) synthesis unit and polyformaldehyde synthesis unit etc.

[0007] The utility model provides a system of producing polyformaldehyde, the system of producing polyformaldehyde according to material transportation direction, in turn includes formaldehyde synthesis unit, trioxymethylene synthesis unit, dioxolane (pentolane) synthesis unit and polyformaldehyde synthesis unit;

[0008] The formaldehyde synthesis unit is connected with trioxymethylene synthesis unit and dioxolane (pentolane) synthesis unit respectively;

[0009] The polyformaldehyde synthesis unit is connected with trioxymethylene synthesis unit and dioxolane (pentolane) synthesis unit respectively.

[0010] Further, the formaldehyde synthesis unit includes raw material mixer, raw material filter, formaldehyde reactor, formaldehyde absorption tower, alcohol removal tower and formaldehyde concentrator connected in turn.

[0011] Further, the raw material filter is equipped with fire prevention device between the formaldehyde reactor.

[0012] Further, the formaldehyde reactor is equipped with heat recovery device between the formaldehyde absorption tower.

[0013] Further, the alcohol removal tower top is further provided with methanol recovery device, and the methanol recovery device is connected with the raw material mixer.

[0014] Further, the methanol recovery device includes methanol condenser, methanol recovery tower and methanol tank, and the methanol tank is connected with the raw material mixer.

[0015] Further, the raw material mixer is provided with steam inlet, methanol feeding port, air inlet and discharge port.

[0016] Further, the raw material filter is provided with feeding port and discharge port, and the feeding port of the raw material filter is connected with the discharge port of the raw material mixer through pipeline.

[0017] Further, the formaldehyde reactor is provided with feeding port and discharge port at the bottom, and the feeding port of the formaldehyde reactor is connected with the discharge port of the raw material filter through pipeline.

[0018] Further, the bottom of the formaldehyde absorption tower is provided with a discharge port, the lower part is provided with a feed port, and the top is provided with a waste gas outlet; the feed port of the formaldehyde absorption tower is connected with the discharge port of the formaldehyde reactor through a pipeline.

[0019] Further, the bottom of the alcohol removal tower is provided with a discharge port, the lower part is provided with a feed port, and the upper part is provided with a gas outlet; the feed port of the alcohol removal tower is connected with the discharge port of the formaldehyde absorption tower through a pipeline.

[0020] Further, the bottom of the formaldehyde condenser is provided with a discharge port, and the lower part is provided with a feed port; the feed port of the formaldehyde condenser is connected with the discharge port of the alcohol removal tower through a pipeline.

[0021] Further, the top of the methanol condenser is provided with a feed port, and the bottom is provided with a discharge port; the feed port of the methanol condenser is connected with the gas outlet of the alcohol removal tower through a pipeline.

[0022] Further, the top of the methanol recovery tower is provided with a feed port, and the bottom is provided with a discharge port; the feed port of the methanol recovery tower is connected with the discharge port of the methanol condenser.

[0023] Further, the top of the methanol tank is provided with a feed port, and the bottom is provided with a discharge port; the feed port of the methanol tank is connected with the discharge port of the methanol recovery tower through a pipeline, and the discharge port of the methanol tank is connected with the methanol feed port of the raw material mixer through a pipeline, and fresh methanol enters the raw material mixer for mixing.

[0024] Further, the triformaldehyde synthesis unit comprises a triformaldehyde reactor, a triformaldehyde concentration tower, a triformaldehyde extraction tower, a triformaldehyde mixing tank, a triformaldehyde light boiling tower, a triformaldehyde heavy boiling tower, a triformaldehyde product tank and a triformaldehyde recovery tank arranged in sequence.

[0025] Further, the material passes through the triformaldehyde reactor, the triformaldehyde concentration tower, the triformaldehyde extraction tower, the triformaldehyde mixing tank, the triformaldehyde light boiling tower and the triformaldehyde heavy boiling tower in sequence, and finally enters the triformaldehyde product tank.

[0026] Further, the triformaldehyde concentration tower is connected with the triformaldehyde reactor in a circulation manner, so that the unreacted material in the triformaldehyde concentration tower can return to the triformaldehyde reactor for continuous reaction.

[0027] Further, a buffer tank is arranged between the triformaldehyde concentration tower and the triformaldehyde extraction tower, which is used for storing intermediate materials.

[0028] Further, the buffer tank between the concentrated formaldehyde tower and the formaldehyde extraction tower is provided with a feed inlet and a discharge outlet, wherein the feed inlet is connected with the discharge outlet of the concentrated formaldehyde tower, and the discharge outlet is connected with the feed inlet of the formaldehyde extraction tower.

[0029] Further, the top of the formaldehyde extraction tower is provided with a formaldehyde inlet, the bottom is provided with a benzene inlet and a waste liquid outlet, and the formaldehyde extraction tower is provided with a discharge outlet; the formaldehyde inlet of the formaldehyde extraction tower is connected with the discharge outlet of the concentrated formaldehyde tower.

[0030] Further, the formaldehyde inlet and the benzene inlet of the formaldehyde extraction tower are countercurrently contacted.

[0031] Further, the waste liquid outlet at the bottom of the formaldehyde extraction tower is connected with the formaldehyde recovery tank to recover formaldehyde.

[0032] Further, a buffer tank is further arranged between the formaldehyde mixing tank and the formaldehyde light boiling tower to store intermediate materials.

[0033] Further, the buffer tank between the formaldehyde mixing tank and the formaldehyde light boiling tower is provided with a feed inlet and a discharge outlet, wherein the feed inlet is connected with the discharge outlet of the formaldehyde mixing tank, and the discharge outlet is connected with the feed inlet of the formaldehyde light boiling tower.

[0034] Further, the top of the formaldehyde light boiling tower is further connected with a benzene storage tank to recover benzene in the formaldehyde light boiling tower.

[0035] Further, the formaldehyde heavy boiling tower is connected with the formaldehyde recovery tank to recover formaldehyde.

[0036] Further, the formaldehyde recovery tank is further connected with a formaldehyde recovery tower, and the formaldehyde recovery tower is connected with the formaldehyde extraction tower to rectify and reuse the recovered formaldehyde.

[0037] Further, the top of the formaldehyde reactor is provided with a discharge outlet, the side is provided with a feed inlet and a circulation port; the feed inlet of the formaldehyde reactor is connected with the discharge outlet of the formaldehyde concentrator.

[0038] Further, the top of the formaldehyde concentrator is provided with a discharge outlet, the side is provided with a feed inlet, and the bottom is provided with a circulation port; the feed inlet of the formaldehyde concentrator is connected with the discharge outlet of the formaldehyde reactor, and the circulation port of the formaldehyde concentrator is connected with the circulation port of the formaldehyde reactor.

[0039] Further, the top of the trioxane mixing tank is provided with a feed inlet, and the bottom is provided with a discharge outlet; the feed inlet of the trioxane mixing tank is connected with the discharge outlet of the trioxane extraction column;

[0040] The discharge outlet of the trioxane mixing tank is connected with a separator for separating benzene and trioxane in the trioxane mixing tank; the separator is provided with a liquid inlet, a liquid outlet and a circulation port; the liquid inlet of the separator is connected with the discharge outlet of the trioxane mixing tank, and the circulation port of the separator is connected with the benzene liquid inlet of the trioxane extraction column.

[0041] Further, the top of the trioxane light boiling column is provided with a benzene liquid outlet, the bottom is provided with a discharge outlet, and the feed inlet; the feed inlet of the trioxane light boiling column is connected with the liquid outlet of the separator.

[0042] Further, the top of the benzene liquid storage tank is provided with a benzene liquid inlet and a benzene liquid outlet; the benzene liquid inlet of the benzene liquid storage tank is connected with the benzene liquid outlet of the trioxane light boiling column.

[0043] Further, the trioxane heavy boiling column is provided with a liquid inlet, the top is provided with a discharge outlet, and the bottom is provided with a waste liquid outlet; the liquid inlet of the trioxane heavy boiling column is connected with the discharge outlet of the trioxane light boiling column.

[0044] Further, the top of the trioxane product tank is provided with a feed inlet, and the bottom is provided with a discharge outlet; the feed inlet of the trioxane product tank is connected with the discharge outlet of the trioxane heavy boiling column.

[0045] Further, the top of the trioxane recovery tank is provided with a feed inlet, and the bottom is provided with a discharge outlet; the feed inlet of the trioxane recovery tank is connected with the waste liquid outlet of the trioxane extraction column and the waste liquid outlet of the trioxane heavy boiling column.

[0046] Further, the dioxolane synthesis unit comprises a dioxolane reactor, a dioxolane concentration column, a dioxolane extraction column, a dioxolane heavy boiling column, a dioxolane light boiling column and a dioxolane product tank arranged in sequence.

[0047] Further, the bottom of the dioxolane extraction column is provided with a dioxolane liquid inlet and a waste alkali port, and the top is provided with a NaOH liquid inlet.

[0048] Further, the materials entering the dioxolane liquid inlet and the NaOH liquid inlet of the dioxolane extraction column are countercurrently contacted.

[0049] Further, the dioxolane synthesis unit is also provided with a waste alkali tank, which is connected with the waste alkali port of the dioxolane extraction tower.

[0050] Further, the dioxolane extraction tower and the dioxolane reboiler tower are also provided with a buffer tank for storing intermediate materials.

[0051] Further, the buffer tank between the dioxolane extraction tower and the dioxolane reboiler tower is provided with an inlet and an outlet, wherein the inlet is connected with the outlet of the dioxolane extraction tower, and the outlet is connected with the inlet of the dioxolane reboiler tower.

[0052] Further, the dioxolane reboiler tower is also connected with the dioxolane reactor for delivering unreacted materials back to the dioxolane reactor for further reaction.

[0053] Further, the dioxolane light reboiler tower is also connected with the dioxolane concentration tower for recovering dioxolane in the gas component of the dioxolane light reboiler tower.

[0054] Further, the dioxolane reactor is provided with a recovery port, a formaldehyde inlet, an ethanol inlet, a catalyst inlet, and an outlet arranged at the top; the formaldehyde inlet of the dioxolane reactor is connected with the outlet of the formaldehyde concentrator.

[0055] Further, the dioxolane concentration tower is provided with an inlet and an outlet arranged at the top; the inlet of the dioxolane concentration tower is connected with the outlet of the dioxolane reactor.

[0056] Further, the dioxolane extraction tower is provided with an outlet at the top; the inlet of the dioxolane extraction tower is connected with the outlet of the dioxolane concentration tower.

[0057] Further, the dioxolane reboiler tower is provided with a recovery port, an inlet, and an outlet arranged at the top; the inlet of the dioxolane reboiler tower is connected with the outlet of the dioxolane extraction tower, the recovery port of the dioxolane reboiler tower is connected with the recovery port of the dioxolane reactor, and the materials enter the dioxolane reactor from the dioxolane reboiler tower.

[0058] Further, the dioxolane light reboiler tower is provided with an inlet and an outlet arranged at the bottom; the inlet of the dioxolane light reboiler tower is connected with the outlet of the dioxolane reboiler tower.

[0059] Further, the dioxolane product tank is provided with a feed inlet and a discharge outlet arranged at the bottom; the feed inlet of the dioxolane product tank is connected with the discharge outlet of the dioxolane light boiling tower.

[0060] Further, the waste alkali tank is provided with a feed inlet; the feed inlet of the waste alkali tank is connected with the waste alkali outlet of the dioxolane extraction tower.

[0061] Further, the polyformaldehyde synthesis unit comprises a polymerization reactor, a pulverizer, a quenching tank, a centrifuge, a dryer and a polyformaldehyde product tank arranged in sequence.

[0062] Further, the material passes through the polymerization reactor, the pulverizer, the quenching tank, the centrifuge and the dryer in sequence.

[0063] Further, the polymerization reactor is provided with a liquid injection port at the bottom; the alkaline liquid enters the polymerization reactor and mixes with the material therein through the liquid injection port.

[0064] Further, the polymerization reactor is provided with an initiator feed inlet, a trioxane feed inlet, a dioxolane feed inlet, a liquid feed inlet and a discharge outlet; the trioxane feed inlet of the polymerization reactor is connected with the discharge outlet of the trioxane product tank; the dioxolane feed inlet of the polymerization reactor is connected with the discharge outlet of the dioxolane product tank; and the discharge outlet of the polymerization reactor is connected with the pulverizer.

[0065] Further, the system for producing polyformaldehyde further comprises a burning unit.

[0066] Further, the burning unit is connected with the formaldehyde synthesis unit, the trioxane synthesis unit, the dioxolane synthesis unit and the polyformaldehyde synthesis unit respectively.

[0067] Further, the burning unit is provided with a gas inlet and a waste gas outlet; the gas inlet of the burning unit is connected with the devices producing waste gas in the formaldehyde synthesis unit, the trioxane synthesis unit, the dioxolane synthesis unit and the polyformaldehyde synthesis unit.

[0068] Further, the system for producing polyformaldehyde further comprises a pellet preparation unit.

[0069] Further, the pellet preparation unit further comprises a product mixer, a double screw extruder, a screening machine, a pellet dryer and a pellet tank.

[0070] Further, the polyformaldehyde product tank is connected with the product mixer.

[0071] Further, the twin-screw extruder is provided with a liquid injection port, and the alkaline liquid enters the twin-screw extruder to mix with the material therein.

[0072] Further, a pump is connected between each device in the system for producing polyformaldehyde.

[0073] The utility model discloses beneficial effect:

[0074] The utility model discloses a plurality of different synthetic units, the preparation of formaldehyde, trioxane, dioxolane (pentolane) and polyformaldehyde forms continuous flow synthetic device, can transport the material of each stage to the next stage through simple operation in the production process, can also carry out the recovery to the unreacted or waste material in the system, and the material after recovery continues to utilize in the last stage, avoids the waste of material also saved the energy consumption of the treatment time of subsequent waste. BRIEF DESCRIPTION OF DRAWINGS

[0075] Figure 1 It is the structural schematic diagram of the system for producing polyformaldehyde in the utility model;

[0076] Figure 2 It is the structural schematic diagram of the formaldehyde synthetic unit in the utility model;

[0077] Figure 3 It is the structural schematic diagram of the trioxane synthetic unit in the utility model;

[0078] Figure 4 It is the structural schematic diagram of the dioxolane (pentolane) synthetic unit system in the utility model;

[0079] Figure 5 It is the structural schematic diagram of the polyformaldehyde synthetic unit system in the utility model;

[0080] The labels and names in the figure are: A, formaldehyde synthesis unit; B, trioxane synthesis unit; C, dioxolane synthesis unit; D, polyformaldehyde synthesis unit; 101, raw material mixer; 102, raw material filter; 103, formaldehyde reactor; 104, formaldehyde absorption tower; 105, alcohol removal tower; 106, formaldehyde concentrator; 201, trioxane reactor; 202, trioxane concentration tower; 203, trioxane extraction tower; 204, trioxane mixing tank; 205, trioxane light boiling tower; 206, trioxane heavy boiling tower; 207, trioxane product tank; 208, trioxane recovery tank; 301, dioxolane reactor; 302, dioxolane concentration tower; 303, dioxolane extraction tower; 304, dioxolane heavy boiling tower; 305, dioxolane light boiling tower; 306, dioxolane product tank; 401, polymerization reactor; 402, crusher; 403, quenching tank; 404, centrifuge; 405, dryer; 406, polyformaldehyde product tank. DETAILED DESCRIPTION

[0081] The utility model is described in detail below in combination with the embodiments:

[0082] The utility model provides a system for producing polyformaldehyde, which greatly improves the efficiency of preparing polyformaldehyde through the cooperation and coordination between different units, and greatly saves energy by recycling waste materials during the preparation process.

[0083] Embodiment 1

[0084] The utility model provides a system for producing polyformaldehyde, which comprises, in sequence according to the material transportation direction, a formaldehyde synthesis unit A, a trioxane synthesis unit B, a dioxolane synthesis unit C, and a polyformaldehyde synthesis unit D.

[0085] The formaldehyde synthesis unit A is connected to the trioxane synthesis unit B and the dioxolane synthesis unit C, respectively.

[0086] The polyformaldehyde synthesis unit D is connected to the trioxane synthesis unit B and the dioxolane synthesis unit C, respectively.

[0087] In this embodiment, the formaldehyde synthesis unit A comprises, in sequence, a raw material mixer 101, a raw material filter 102, a formaldehyde reactor 103, a formaldehyde absorption tower 104, an alcohol removal tower 105, and a formaldehyde concentrator 106.

[0088] A fireproof device is installed between the raw material filter 102 and the formaldehyde reactor 103.

[0089] A heat recovery device is installed between the formaldehyde reactor 103 and the formaldehyde absorption tower 104.

[0090] The top of the alcohol removal tower 105 is also provided with a methanol recovery device connected to the raw material mixer 101;

[0091] The methanol recovery device includes a methanol condenser, a methanol recovery tower, and a methanol tank, and the methanol tank is connected to the raw material mixer 101;

[0092] The raw material mixer 101 is provided with a steam inlet, a methanol inlet, an air inlet, and a discharge outlet;

[0093] The raw material filter 102 is provided with an inlet and an outlet, and the inlet of the raw material filter 102 is connected to the outlet of the raw material mixer 101 through a pipeline;

[0094] The methanal reactor 103 is provided with an inlet on the side and an outlet at the bottom, and the inlet of the methanal reactor 103 is connected to the outlet of the raw material filter 102 through a pipeline;

[0095] The bottom of the methanal absorption tower 104 is provided with an outlet, the lower part is provided with an inlet, and the top is provided with a waste gas outlet; the inlet of the methanal absorption tower 104 is connected to the outlet of the methanal reactor 103 through a pipeline;

[0096] The bottom of the alcohol removal tower 105 is provided with an outlet, the lower part is provided with an inlet, and the upper part is provided with a gas outlet; the inlet of the alcohol removal tower 105 is connected to the outlet of the methanal absorption tower 104 through a pipeline;

[0097] The bottom of the methanal condenser 106 is provided with an outlet, and the lower part is provided with an inlet; the inlet of the methanal condenser 106 is connected to the outlet of the alcohol removal tower 105 through a pipeline;

[0098] The top of the methanol condenser is provided with an inlet, and the bottom is provided with an outlet; the inlet of the methanol condenser is connected to the gas outlet of the alcohol removal tower 105 through a pipeline;

[0099] The top of the methanol recovery tower is provided with an inlet, and the bottom is provided with an outlet; the inlet of the methanol recovery tower is connected to the outlet of the methanol condenser;

[0100] The top of the methanol tank is provided with an inlet, and the bottom is provided with an outlet; the inlet of the methanol tank is connected to the outlet of the methanol recovery tower through a pipeline, and the outlet of the methanol tank is connected to the methanol inlet of the raw material mixer 101 through a pipeline, and fresh methanol is mixed into the raw material mixer 101;

[0101] The trioxane synthesis unit B comprises, in sequence, a trioxane reactor 201, a trioxane concentration tower 202, a trioxane extraction tower 203, a trioxane mixing tank 204, a trioxane light boiling tower 205, a trioxane heavy boiling tower 206, a trioxane product tank 207 and a trioxane recovery tank 208;

[0102] The materials pass through the trioxane reactor 201, the trioxane concentration tower 202, the trioxane extraction tower 203, the trioxane mixing tank 204, the trioxane light boiling tower 205 and the trioxane heavy boiling tower 206 in sequence, and finally enter the trioxane product tank 207;

[0103] The trioxane concentration tower 202 is circularly connected with the trioxane reactor 201, so that the unreacted materials in the trioxane concentration tower 202 can return to the trioxane reactor 201 for further reaction;

[0104] A buffer tank is further arranged between the trioxane concentration tower 202 and the trioxane extraction tower 203, for storing intermediate materials;

[0105] A trioxane liquid inlet is arranged at the top of the trioxane extraction tower 203, and a benzene liquid inlet and a waste liquid outlet are arranged at the bottom of the trioxane extraction tower 203;

[0106] The materials entering the trioxane liquid inlet and the benzene liquid inlet of the trioxane extraction tower 203 are countercurrently contacted;

[0107] The waste liquid outlet at the bottom of the trioxane extraction tower 203 is connected with the trioxane recovery tank 208, so that the trioxane can be recovered;

[0108] A buffer tank is further arranged between the trioxane mixing tank 204 and the trioxane light boiling tower 205, for storing intermediate materials;

[0109] The buffer tank between the trioxane mixing tank 204 and the trioxane light boiling tower 205 is provided with a feeding port and a discharging port, wherein the feeding port is connected with the discharging port of the trioxane mixing tank 204, and the discharging port is connected with the feeding port of the trioxane light boiling tower 205;

[0110] A benzene storage tank is further connected with the top of the trioxane light boiling tower 205, for recovering the benzene in the trioxane light boiling tower 205;

[0111] The trioxane heavy boiling tower 206 is connected with the trioxane recovery tank 208, so that the trioxane can be recovered;

[0112] The trioxane recovery tank 208 is also connected with a trioxane recovery column, which is connected with the trioxane extraction column 203 to rectify and reuse the recovered trioxane;

[0113] The trioxane reactor 201 is provided with a discharge port at the top and a feed inlet and a circulation port at the side; the feed inlet of the trioxane reactor 201 is connected with the discharge port of the formaldehyde concentrator 106;

[0114] The trioxane concentrator 202 is provided with a discharge port at the top, a feed inlet at the side, and a circulation port at the bottom; the feed inlet of the trioxane concentrator 202 is connected with the discharge port of the trioxane reactor 201, and the circulation port of the trioxane concentrator 202 is connected with the circulation port of the trioxane reactor 201;

[0115] The trioxane extraction column 203 is provided with a discharge port; the trioxane liquid inlet of the trioxane extraction column 203 is connected with the discharge port of the trioxane concentrator 202;

[0116] The trioxane mixing tank 204 is provided with a feed inlet at the top and a discharge port at the bottom; the feed inlet of the trioxane mixing tank 204 is connected with the discharge port of the trioxane extraction column 203;

[0117] The discharge port of the trioxane mixing tank 204 is connected with a separator for separating benzene and trioxane in the trioxane mixing tank 204; the separator is provided with a liquid inlet, a liquid outlet, and a circulation port; the liquid inlet of the separator is connected with the discharge port of the trioxane mixing tank 204, and the circulation port of the separator is connected with the benzene liquid inlet of the trioxane extraction column 203;

[0118] The trioxane light boiling column 205 is provided with a benzene liquid outlet at the top, a discharge port at the bottom, and a feed inlet; the feed inlet of the trioxane light boiling column 205 is connected with the discharge port of the trioxane mixing tank 204;

[0119] The benzene storage tank is provided with a benzene liquid inlet and a benzene liquid outlet at the top; the benzene liquid inlet of the benzene storage tank is connected with the benzene liquid outlet of the trioxane light boiling column 205;

[0120] The trioxane heavy boiling column 206 is provided with a liquid inlet, a discharge port at the top, and a waste liquid port at the bottom; the liquid inlet of the trioxane heavy boiling column 206 is connected with the discharge port of the trioxane light boiling column 205;

[0121] The trioxane product tank 207 is provided with a feed inlet at the top and a discharge port at the bottom; the feed inlet of the trioxane product tank 207 is connected with the discharge port of the trioxane heavy boiling column 206.

[0122] The triformylmethane recovery tank 208 is provided with a feed inlet at the top and a discharge outlet at the bottom; the feed inlet of the triformylmethane recovery tank 208 is connected with the waste liquid outlet of the triformylmethane extraction column 203 and the waste liquid outlet of the triformylmethane reboiler column 206;

[0123] The dioxopentacyclo ring synthesis unit C comprises, in sequence, a dioxopentacyclo ring reactor 301, a dioxopentacyclo ring concentration column 302, a dioxopentacyclo ring extraction column 303, a dioxopentacyclo ring reboiler column 304, a dioxopentacyclo ring light boiling column 305, and a dioxopentacyclo ring product tank 306;

[0124] The dioxopentacyclo ring extraction column 303 is provided with a dioxopentacyclo ring liquid inlet and a waste alkali outlet at the bottom, and a NaOH liquid inlet at the top;

[0125] The materials entering the dioxopentacyclo ring liquid inlet and the NaOH liquid inlet of the dioxopentacyclo ring extraction column 303 are countercurrently contacted;

[0126] The dioxopentacyclo ring synthesis unit C is further provided with a waste alkali tank, which is connected with the waste alkali outlet of the dioxopentacyclo ring extraction column 303;

[0127] A buffer tank is further arranged between the dioxopentacyclo ring extraction column 303 and the dioxopentacyclo ring reboiler column 304, for storing intermediate materials;

[0128] The buffer tank between the dioxopentacyclo ring extraction column 303 and the dioxopentacyclo ring reboiler column 304 is provided with a feed inlet and a discharge outlet, wherein the feed inlet is connected with the discharge outlet of the dioxopentacyclo ring extraction column 303, and the discharge outlet is connected with the feed inlet of the dioxopentacyclo ring reboiler column 304;

[0129] The dioxopentacyclo ring reboiler column 304 is further connected with the dioxopentacyclo ring reactor 301, for delivering unreacted materials back to the dioxopentacyclo ring reactor 301 for continuous reaction;

[0130] The dioxopentacyclo ring light boiling column 305 is further connected with the dioxopentacyclo ring concentration column 302, for recovering dioxopentacyclo ring in the gas component of the dioxopentacyclo ring light boiling column 305;

[0131] The dioxopentacyclo ring reactor 301 is provided with a recovery port, a formaldehyde feed inlet, an ethanol feed inlet, a catalyst inlet, and a discharge outlet arranged at the top; the formaldehyde feed inlet of the dioxopentacyclo ring reactor 301 is connected with the discharge outlet of the formaldehyde concentrator 106;

[0132] The dioxolane (pentolane) concentration tower 302 is provided with a feed inlet and a discharge outlet arranged at the top; the feed inlet of the dioxolane (pentolane) concentration tower 302 is connected with the discharge outlet of the dioxolane (pentolane) reactor 301;

[0133] The dioxolane (pentolane) extraction tower 303 is provided with a discharge outlet at the top; the liquid inlet of the dioxolane (pentolane) extraction tower 303 is connected with the discharge outlet of the dioxolane (pentolane) concentration tower 302;

[0134] The dioxolane (pentolane) reboiler tower 304 is provided with a recovery outlet, a feed inlet and a discharge outlet arranged at the top; the feed inlet of the dioxolane (pentolane) reboiler tower 304 is connected with the discharge outlet of the dioxolane (pentolane) extraction tower 303, the recovery outlet of the dioxolane (pentolane) reboiler tower 304 is connected with the recovery outlet of the dioxolane (pentolane) reactor 301, and the material enters the dioxolane (pentolane) reactor 301 from the dioxolane (pentolane) reboiler tower 304;

[0135] The dioxolane (pentolane) light boiling tower 305 is provided with a feed inlet and a discharge outlet arranged at the bottom; the feed inlet of the dioxolane (pentolane) light boiling tower 305 is connected with the discharge outlet of the dioxolane (pentolane) reboiler tower 304;

[0136] The dioxolane (pentolane) product tank 306 is provided with a feed inlet and a discharge outlet arranged at the bottom; the feed inlet of the dioxolane (pentolane) product tank 306 is connected with the discharge outlet of the dioxolane (pentolane) light boiling tower 305;

[0137] The waste alkali tank is provided with a feed inlet, and the feed inlet of the waste alkali tank is connected with the waste alkali outlet of the dioxolane (pentolane) extraction tower 303;

[0138] The polyformaldehyde synthesis unit D comprises a polymerization reactor 401, a pulverizer 402, a quenching tank 403, a centrifuge 404, a drying machine 405 and a polyformaldehyde product tank 406 arranged in sequence;

[0139] The material sequentially passes through the polymerization reactor 401, the pulverizer 402, the quenching tank 403, the centrifuge 404 and the drying machine 405;

[0140] The bottom of the polymerization reactor 401 is provided with a liquid injection port, and the alkaline liquid enters the polymerization reactor 401 to mix with the material therein through the liquid injection port;

[0141] The polymerization reactor 401 is provided with an initiator feed port, a trioxane feed port, a dioxolane feed port, a liquid feed port and a discharge port; the trioxane feed port of the polymerization reactor 401 is connected with the discharge port of the trioxane product tank 207, the dioxolane feed port of the polymerization reactor 401 is connected with the discharge port of the dioxolane product tank 306, and the discharge port of the polymerization reactor 401 is connected with the pulverizer 402;

[0142] The system for producing polyformaldehyde further comprises a burning unit;

[0143] The burning unit is connected with the formaldehyde synthesis unit A, the trioxane synthesis unit B, the dioxolane synthesis unit C and the polyformaldehyde synthesis unit D respectively;

[0144] The burning unit is provided with a gas inlet and a waste gas outlet, and the gas inlet of the burning unit is connected with devices that produce waste gas in the formaldehyde synthesis unit A, the trioxane synthesis unit B, the dioxolane synthesis unit C and the polyformaldehyde synthesis unit D;

[0145] The system for producing polyformaldehyde further comprises a pellet preparation unit;

[0146] The pellet preparation unit further comprises a product mixer, a double-screw extruder, a screening machine, a pellet dryer and a pellet tank;

[0147] The polyformaldehyde product tank 406 is connected with the product mixer;

[0148] The double-screw extruder is provided with a liquid injection port, and the alkaline liquid enters the double-screw extruder to mix with the materials therein through the liquid injection port.

[0149] In the utility model, after methanol, steam and air are mixed through the raw material mixer 101, the mixture is filtered through the raw material filter 102 and enters the formaldehyde reactor 103 through the fireproof device, and under the catalysis of silver catalyst, the mixture is reacted by releasing heat, the heat of the formaldehyde reactor 103 is recovered by the heat recovery device, the material prepared by the formaldehyde reactor 103 enters the formaldehyde absorption tower 104 to be absorbed by desalted water, and crude formaldehyde is obtained, the crude formaldehyde enters the alcohol removal tower 105 under negative pressure to remove unreacted methanol, and refined methanol is obtained, the unreacted methanol enters the methanol recovery device, the recovered methanol enters the raw material mixer 101 to circulate and react, and the refined methanol enters the formaldehyde concentrator 106 from the alcohol removal tower 105;

[0150] In the trioxane reactor 201, the refined methanol enters the trioxane reactor 201 to produce trioxane under the action of sulfuric acid catalyst, the trioxane crude product enters the trioxane concentration column 202 to be rectified under negative pressure, the unreacted material returns to the trioxane reactor 201 to continue the reaction, when the concentration of the material at the top of the trioxane concentration column 202 is 40%±5%, the material at the top of the trioxane concentration column 202 is pumped to the buffer tank and then to the trioxane extraction column 203, the material at the bottom of the trioxane concentration column 202 is pumped back to the trioxane reactor 201 to continue the reaction, the material at the top of the trioxane concentration column 202 is fed into the trioxane extraction column 203 through the trioxane inlet at the top of the trioxane extraction column 203, the benzene extraction liquid is pumped into the trioxane extraction column 203 through the benzene inlet at the bottom of the trioxane extraction column 203, wherein the material at the top of the trioxane extraction column 203 is in countercurrent contact with the benzene extraction liquid for extraction, the extracted material enters the trioxane mixing tank 204, the waste liquid after extraction enters the trioxane recovery tank 208 through the waste liquid outlet at the bottom of the trioxane extraction column 203 to recover trioxane, the material in the trioxane mixing tank 204 is separated through the separator, the separated benzene extraction liquid enters the trioxane extraction column for recycling, the other separated liquid enters the trioxane light boiling tower 205 through the buffer tank, the material rectified in the trioxane light boiling tower 205 enters the trioxane heavy boiling tower 206 through the bottom of the trioxane light boiling tower 205, the benzene at the top of the trioxane light boiling tower 205 enters the benzene storage tank, the trioxane in the trioxane heavy boiling tower 206 enters the trioxane product tank 207 to obtain trioxane, the material at the bottom of the trioxane heavy boiling tower 206 returns to the trioxane recovery tank 208 to recover trioxane, the recovered trioxane in the trioxane recovery tank 208 has a mass fraction of 12%, enters the trioxane recovery column 208 to be rectified to obtain recovered trioxane with a mass fraction of 45%, and then the recovered trioxane with a mass fraction of 45% is pumped into the trioxane extraction column 203 for reuse; the material returns to the trioxane heavy boiling tower 206 to continue rectification;

[0151] In the dioxolane reactor 301, the refined formaldehyde in the formaldehyde synthesis unit A enters the dioxolane reactor 301, and the ethylene glycol and the refined formaldehyde are reacted in the dioxolane reactor 301 under the action of sulfuric acid catalyst to obtain a 60% mass fraction dioxolane solution, the 60% mass fraction dioxolane solution enters the dioxolane concentration column 302 from the dioxolane reactor 301, and the 92% mass fraction dioxolane solution is obtained by rectification in the dioxolane concentration column 302, the 92% mass fraction dioxolane solution is pumped from the top of the dioxolane concentration column 302 to the dioxolane extraction column 303, in the dioxolane extraction column 303, the 92% mass fraction dioxolane solution is fed from the dioxolane inlet at the bottom of the dioxolane extraction column 303, NaOH is fed from the NaOH inlet at the top of the dioxolane extraction column 303, the 92% mass fraction dioxolane solution is countercurrently contacted with the NaOH, the water content in the 92% mass fraction dioxolane solution is reduced to 5% to obtain refined dioxolane, the reacted NaOH enters the waste alkali tank from the waste alkali port of the dioxolane extraction column 303, the refined dioxolane enters the buffer tank and is pumped into the dioxolane rectification column 304 to obtain a 99% mass fraction refined dioxolane, the unreacted recovered material in the dioxolane rectification column 304 enters the dioxolane reactor 301 for reaction, the 99% mass fraction refined dioxolane is pumped from the dioxolane rectification column 304 to the dioxolane light boiling column 305, and the refined dioxolane with a mass fraction of 99.9% obtained in the dioxolane light boiling column 305 enters the dioxolane product tank 306 for storage, and the unreacted 92% mass fraction dioxolane solution in the dioxolane light boiling column 305 returns to the dioxolane reactor 301 for reaction;

[0152] The trioxymethylene and 99.9% refined dioxolane (pentolane) prepared by the trioxymethylene synthesis unit B and the dioxolane (pentolane) synthesis unit C enter the polymerization reactor 401, and polymerization reaction occurs under the initiation of boron trifluoride, while a TEA alkaline solution is injected into the polymerization reactor 401 to prevent HCHO converted into HCOOH by terminal dissociation, causing polymer chain breaking and causing the molecular weight to be reduced, the pH is controlled to be 8-10, the reaction rate is 65%, and flaky crude polyoxymethylene is obtained, which enters the pulverizer 402 from the polymerization reactor 401, is centrifuged by the centrifugal machine 404, is dried by the drying machine 405, and is finally stored in the polyoxymethylene product tank 406.

[0153] In the embodiment, each device is connected to a burning unit, and the waste after unreacted or extraction enters the burning unit for burning treatment.

[0154] The embodiment also includes a pellet preparation unit, and the powdery polyoxymethylene in the polyoxymethylene product tank 406 is mixed with a stabilizer in the product mixer, then enters the double-screw extruder for extrusion, is screened by the screening machine, is dried by the pellet dryer, and is finally stored in the pellet tank.

[0155] According to the above, the polyoxymethylene production system has a very wide range of use, low cost, and high market prospect.

[0156] The above is only a preferred embodiment of the utility model, and does not limit the utility model in any other form, and any modification or equivalent change made according to the technical essence of the utility model still belongs to the scope of the utility model claimed.

Claims

1. A system for producing polyoxymethylene, characterized in that, The system for producing polyoxymethylene includes, in sequence, a formaldehyde synthesis unit (A), a trioxymethylene synthesis unit (B), a dioxane synthesis unit (C), and a polyoxymethylene synthesis unit (D), according to the material transport direction. The formaldehyde synthesis unit (A) is connected to the trioxymethylene synthesis unit (B) and the dioxane synthesis unit (C), respectively; The polyoxymethylene synthesis unit (D) is connected to the trioxymethylene synthesis unit (B) and the dioxopentane synthesis unit (C), respectively.

2. The system for producing polyoxymethylene according to claim 1, characterized in that, The formaldehyde synthesis unit (A) includes a raw material mixer (101), a raw material filter (102), a formaldehyde reactor (103), a formaldehyde absorption tower (104), an alcohol removal tower (105), and a formaldehyde concentrator (106) connected in sequence.

3. The system for producing polyoxymethylene according to claim 2, characterized in that, A heat recovery device is installed between the formaldehyde reactor (103) and the formaldehyde absorption tower (104).

4. The system for producing polyoxymethylene according to claim 1, characterized in that, The trioxymethylene synthesis unit (B) includes, in sequence, a trioxymethylene reactor (201), a trioxymethylene concentration tower (202), a trioxymethylene extraction tower (203), a trioxymethylene mixing tank (204), a trioxymethylene light boiling tower (205), a trioxymethylene reboiling tower (206), a trioxymethylene product tank (207), and a trioxymethylene recovery tank (208).

5. The system for producing polyoxymethylene according to claim 4, characterized in that, The trioxymethylene concentration tower (202) is cyclically connected to the trioxymethylene reactor (201) so that unreacted material in the trioxymethylene concentration tower (202) can be returned to the trioxymethylene reactor (201) for further reaction.

6. The system for producing polyoxymethylene according to claim 4, characterized in that, The top of the trioxymethylene extraction tower (203) is provided with a trioxymethylene inlet, and the bottom is provided with a benzene inlet and a waste liquid outlet.

7. The system for producing polyoxymethylene according to claim 4, characterized in that, The trioxymethylene reboiler (206) is connected to the trioxymethylene recovery tank (208) for the recovery of trioxymethylene.

8. The system for producing polyoxymethylene according to claim 1, characterized in that, The dioxapentane synthesis unit (C) includes a dioxapentane reactor (301), a dioxapentane concentration tower (302), a dioxapentane extraction tower (303), a dioxapentane reboiling tower (304), a dioxapentane light boiling tower (305), and a dioxapentane product tank (306) arranged sequentially.

9. The system for producing polyoxymethylene according to claim 3, characterized in that, The dioxapentane reboiler (304) is also connected to the dioxapentane reactor (301) for transporting unreacted materials back to the dioxapentane reactor (301) for further reaction.

10. The system for producing polyoxymethylene according to claim 1, characterized in that, The polyoxymethylene synthesis unit (D) includes a polymerization reactor (401), a pulverizer (402), a quench tank (403), a centrifuge (404), a dryer (405), and a polyoxymethylene product tank (406) arranged in sequence.

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