CN210215201U

CN210215201U - Formaldehyde production process unit

Info

Publication number: CN210215201U
Application number: CN201821576745.2U
Authority: CN
Inventors: Jiayong Xiang; 向家勇
Original assignee: Three Li Hubei Sweetgum Science And Technology Ltd
Current assignee: Jiangsu Jiuhong Chemical Technology Co., Ltd
Priority date: 2018-09-27
Filing date: 2018-09-27
Publication date: 2020-03-31
Anticipated expiration: 2028-09-27

Abstract

The utility model discloses a formaldehyde production process units and method, the device includes methanol evaporator, over heater, blender, flame retardant ware and the oxidizer that connects gradually through the tubing pump, the export of oxidizer has still connected gradually waste heat recovery heat exchanger, formaldehyde condenser, formaldehyde absorption tower and formaldehyde evaporator through the tubing pump, realizes not having the parking change on line through movable silver catalysis net and has improved production efficiency greatly, sends into the oxidizer through the direct heat transfer gasification circulation with rare formaldehyde solution simultaneously to avoid the absorption process to bring moisture for the system, thereby improved reaction efficiency and yield.

Description

Formaldehyde production process unit

Technical Field

The invention belongs to the technical field of chemical environmental protection, and particularly relates to a formaldehyde production process device and a formaldehyde production method.

Background

The existing silver method formaldehyde comprises a reboiler method and a bubbling method. The reboiler method consumes a large amount of steam and is gradually eliminated at present. The methanol evaporator by the bubbling method comprises a methanol evaporator, a methanol circulating pump, a superheater, a blending steam distributor, a mixing filter, a flame arrester and the like. The evaporation of the methanol is that air passes through a methanol liquid layer in an evaporator and bubbles the methanol liquid, the methanol in the evaporator is pumped out through a methanol circulating pump to exchange heat with formaldehyde to realize the vaporization of the methanol, the vaporized methanol is mixed with externally added ingredient steam and tail gas, the mixture is superheated to more than 100 ℃ through steam by a superheater and is completely vaporized, the mixture is sent into an oxidizer to react, and the oxidized reaction gas is absorbed by water through a multistage absorption tower to obtain a formaldehyde solution with the mass concentration of 37-52%.

The prior art has the following disadvantages: (1) in a silver-method formaldehyde oxidizer, the reaction temperature is 600-700 ℃, a methanol/air/steam reaction material enters a tube pass after undergoing an oxidation reaction in a silver catalyst bed layer and is cooled to 150-180 ℃, so that the thermal stress of a tube plate section of the oxidizer is extremely high, the service life of the oxidizer is usually 1-2 years, the maximum service life of the oxidizer cannot exceed 3 years, and the yield is limited; (2) after the oxidized formaldehyde mixed gas is absorbed by water in a secondary absorption tower, the waste heat of the formaldehyde mixed gas is not fully recycled, more importantly, the formaldehyde concentration is usually between 37 and 52 percent by directly adopting water absorption, and a high-concentration formaldehyde solution cannot be obtained; (3) the water absorbed by the formaldehyde oxidation is continuously supplemented, and the concentration of the formaldehyde solution is limited to be improved.

Disclosure of Invention

The purpose of the invention is as follows: aiming at the existing problems and defects, the invention aims to provide a formaldehyde production process device.

The technical scheme is as follows: in order to solve the technical problems, the invention adopts the following technical scheme: the utility model provides a formaldehyde production process units, includes methanol evaporator, over heater, blender, flame retardant ware and the oxidizer that connects gradually through the tubing pump, the export of oxidizer still has connected gradually waste heat recovery heat exchanger, formaldehyde condenser, formaldehyde absorption tower and formaldehyde evaporator through the tubing pump, wherein:

the formaldehyde condenser is a shell-and-tube heat exchanger, the shell-and-tube heat exchanger is provided with a heat exchanger shell pass for circulating a reaction product of the oxidizer and a heat exchanger tube pass for circulating a heat exchange medium for absorbing waste heat, the bottom and the top of the heat exchanger shell pass are respectively provided with a formaldehyde extraction port and a condenser gas outlet, the heat exchanger shell pass is also provided with a spray head, and the spray head is circularly communicated with the bottom of the heat exchanger shell pass through a pipeline pump; the formaldehyde extraction port is also connected with a deacidification tower through a pipeline pump;

the formaldehyde evaporator is provided with a steam inlet, and a gas outlet of the formaldehyde evaporator is connected with the steam inlet of the mixer.

Preferably, the methanol evaporator is a bubbling evaporator and comprises an evaporator body, the evaporator body is provided with an air inlet, a methanol gas outlet and a heat exchange coil, the air inlet is connected with a gas distributor located below the liquid level of methanol, and the methanol gas outlet is connected with a superheater.

Preferably, the gas outlet of the condenser is sequentially connected with a heat exchange coil of the methanol evaporator and the formaldehyde absorption tower through pipelines.

Preferably, the waste heat recovery heat exchanger comprises a primary heat exchanger and a secondary heat exchanger which are connected in series.

Preferably, the air inlet of the methanol evaporator is further connected with a methanol washing tower, the bottom and the top of the methanol washing tower are respectively provided with an air inlet and a methanol spray head, the methanol spray head is communicated with the bottom of the tower body through a pipeline pump, and the top of the methanol washing tower is also provided with an air outlet connected with the air inlet of the methanol evaporator.

Preferably, the bottom of the formaldehyde absorption tower is circularly communicated with the top of the tower through a pipeline and a liquid pump, a condensation heat exchanger is arranged on the pipeline, and the bottom of the methanol washing tower is communicated with the condensation heat exchanger through a pipeline pump.

Preferably, the oxidizer comprises a silver catalyst layer, a tank body, a cooling pipe vertically arranged in the tank body, a pipe plate and a sealing head arranged at two ends of the cooling pipe, wherein a feeding hole is formed in the side surface of the lower part of the tank body, a first sealed chamber and a second sealed chamber are respectively arranged on the outer wall of the tank body corresponding to the feeding hole and below the feeding hole in a surrounding manner, the silver catalyst layer comprises at least two connected first silver catalytic mesh layers and second silver catalytic mesh layers, and the first silver catalytic mesh layers and the second silver catalytic mesh layers are respectively arranged in the first sealed chamber and the second sealed chamber; the silver catalyst layer is also provided with a lifting device.

Preferably, the second closed chamber is filled with inert gas, and the gas pressure of the second closed chamber is higher than that of the feed port.

Drawings

FIG. 1 is a schematic structural diagram of a formaldehyde production process apparatus according to the present invention;

FIG. 2 is a schematic view of the structure of the formaldehyde oxidizer of the present invention.

The system comprises a methanol washing tower 1, a methanol evaporator 2, a gas distributor 3, a superheater 4, a mixing filter 5, a formaldehyde oxidizer 6, a first closed chamber 61, a second closed chamber 62, a first silver catalytic mesh layer 63, a second silver catalytic mesh layer 64, a primary heat exchanger 7, a secondary heat exchanger 8, a formaldehyde condenser 9, a deacidification tower 10, a formaldehyde absorption tower 11 and a formaldehyde evaporator 12.

Detailed Description

The present invention is further illustrated by the following figures and specific examples, which are to be understood as illustrative only and not as limiting the scope of the invention, which is to be given the full breadth of the appended claims and any and all equivalent modifications thereof which may occur to those skilled in the art upon reading the present specification.

The silver method formaldehyde production process taking methanol as raw material mainly comprises the following steps: evaporating methanol, mixing formaldehyde, air and water vapor, filtering, overheating, oxidizing the methanol, absorbing the formaldehyde and the like. As shown in FIG. 1, the formaldehyde production process apparatus of the present invention is described in detail in conjunction with the formaldehyde production process apparatus:

the methanol evaporation adopts an air bubbling method, and because the air contains soluble and insoluble impurities, the silver catalyst is adversely affected during the oxidation reaction, so that the activity and the service life of the silver catalyst are shortened. The method circularly sprays and washes the fed air through the methanol washing tower, so that impurities in the air are absorbed to reduce pollution of the silver catalyst, the temperature of the air fed into the washing tower is 10-50 ℃, the methanol is evaporated to realize temperature reduction after washing, and the temperature can reach about 10 ℃ when the balance is achieved, thereby obtaining a low-temperature cold source.

The washed air is sent into a methanol evaporator for bubbling through a distributor, the methanol is evaporated under the heating action of a heat exchange coil to obtain a mixed gas of the methanol and the air, then the mixed gas is sent into a mixing filter through a superheater, water vapor is sent into the mixing filter for mixing and filtering, and then the mixed gas is sent into a formaldehyde oxidizer for oxidizing through a silver method to obtain the formaldehyde. Compared with a common oxidizer, the oxidizer adopts lower feeding, the material is taken on a shell pass, and cooling water enters a tube pass from the bottom through a cooling tube, so that the input amount of the material is obviously increased, and the yield is higher.

As the preferred, with the silver catalyst layer all around the jar body by a plurality of silver catalysis stratum reticulare along circumference constitution, can conveniently change the silver catalyst to need not the parking and change, improved efficiency greatly. Preferably, each silver catalysis net layer is arranged in the first closed chamber or the second closed chamber relative to the position of the feed port, the first silver catalysis net layer is arranged in the first closed chamber and corresponds to the position of the feed port, one end of the first silver catalysis net layer is connected with the second silver catalysis net layer, and the other end of the first silver catalysis net layer is provided with a lifting device. One end that first airtight chamber and second airtight chamber contacted with silver catalyst layer is provided with the opening with silver catalyst layer complex, conveniently changes silver catalyst layer. Utilize hoisting device to promote the second silver catalysis stratum reticulare upwards from the opening part, slowly replace original silver catalysis stratum reticulare, adopt this mode moreover, conveniently realize automatic the change. The lifting device can be realized by various means in the prior art, such as a linear motor (not shown in the figure), and the output end of the lifting device can be directly used for pushing the second silver catalytic mesh layer, and the second silver catalytic mesh layer pushes the original silver catalytic mesh layer until the second silver catalytic mesh layer is replaced by the original silver catalytic mesh layer, so that the silver catalyst is replaced. And a stepping motor can be adopted, and the output end of the stepping motor is changed into linear output by adopting the existing transmission mechanism, so that the second silver catalytic mesh layer is pushed. Wherein, set up hoisting device in the first airtight chamber of silver catalyst layer below, can effectively avoid the influence of the jar body after the heating to hoisting device.

Preferably, the first closed chamber and/or the second closed chamber are filled with inert gas, and the pressure of the inert gas is higher than the atmospheric pressure, so that no outside air enters. And filling inert gas into the first closed chamber and/or the second closed chamber to prevent the gas in the feed inlet from leaking into the first closed chamber and/or the second closed chamber.

Preferably, the cooling pipes in the oxidizer are wound with each other, so that the cooling area of the cooling pipes can be greatly increased, the stress at two ends of the cooling pipes can be effectively reduced, and the service life of the oxidizer is prolonged.

After materials are oxidized in the oxidizer, mixed gas containing formaldehyde and unreacted methanol, nitrogen, water vapor and hydrogen is obtained from the outlet of the formaldehyde oxidizer, the pressure of the mixed gas of formaldehyde at the outlet of the formaldehyde oxidizer can reach 4KG, the temperature can reach 180 ℃, heat exchange is carried out through a two-stage heat exchanger, high-pressure steam with the pressure of 4KG and low-pressure steam with the pressure of 0.5KG can be obtained, the low-pressure steam is used as an oxidation reaction raw material for supplementing, and therefore the waste heat of the mixed gas of formaldehyde is fully utilized.

Another innovation point of the invention is that: the formaldehyde mixed gas is sent into a formaldehyde condenser to be directly condensed to replace a primary formaldehyde absorption tower in the prior art, water absorption and water bringing can be avoided by directly condensing the extracted formaldehyde product, so that a formaldehyde solution with the concentration of 58% can be obtained, and the extracted formaldehyde solution is deacidified in a deacidification tower, so that the acidity of the formaldehyde solution is ensured to be below 10ppm and used as the formaldehyde product. In the direct condensation process, formaldehyde liquid is circularly sprayed in the shell pass of the condenser, so that a liquid film is formed on the tube wall to accelerate the condensation of formaldehyde gas, and the mixed gas which is not completely condensed is continuously sent into a formaldehyde absorption tower to be absorbed, so that a 37-52% dilute formaldehyde solution is obtained.

The invention has another innovation point that: the obtained dilute formaldehyde solution is evaporated by an evaporator and is sent to a mixing filter as a reactant ingredient of a formaldehyde oxidizer to participate in an oxidation reaction, so that compared with the prior art, in the formaldehyde production process, the addition amount of water is greatly reduced for recycling water vapor, and the concentration of formaldehyde is improved.

In addition, the low-temperature methanol with the temperature of about 10 ℃ obtained in the methanol washing tower can be used for the temperature of water absorption in the formaldehyde absorption tower in the cold region, thereby improving the formaldehyde absorption efficiency. The lower the tail gas temperature, the higher the absorption yield and the less product is taken away by the tail gas.

Claims

1. The utility model provides a formaldehyde production process units, includes methanol evaporator, over heater, blender, flame retardant ware and the oxidizer that connects gradually through the tubing pump, its characterized in that: the export of oxidizer still connects gradually waste heat recovery heat exchanger, formaldehyde condenser, formaldehyde absorption tower and formaldehyde evaporator through the tubing pump, wherein:

2. The formaldehyde production process unit according to claim 1, characterized in that: the methanol evaporator is a bubbling evaporator and comprises an evaporator body, the evaporator body is provided with an air inlet, a methanol gas outlet and a heat exchange coil, the air inlet is connected with a gas distributor located below the liquid level of methanol, and the methanol gas outlet is connected with a superheater.

3. The formaldehyde production process unit according to claim 2, characterized in that: the gas outlet of the condenser is sequentially connected with a heat exchange coil of the methanol evaporator and the formaldehyde absorption tower through a pipeline; the waste heat recovery heat exchanger comprises a primary heat exchanger and a secondary heat exchanger which are connected in series.

4. The formaldehyde production process unit according to claim 2, characterized in that: the air inlet of methyl alcohol evaporimeter still is connected with the methyl alcohol scrubbing tower, the tower body bottom and the top of methyl alcohol scrubbing tower are air intlet and methyl alcohol shower nozzle respectively, the methyl alcohol shower nozzle passes through tubing pump and tower body bottom UNICOM, the top of methyl alcohol scrubbing tower still is equipped with the air outlet of being connected with methyl alcohol evaporimeter air inlet.

5. The formaldehyde production process unit according to claim 4, characterized in that: the bottom of the formaldehyde absorption tower is circularly communicated with the top of the tower through a pipeline and a liquid pump, a condensation heat exchanger is arranged on the pipeline, and the bottom of the methanol washing tower is communicated with the condensation heat exchanger through a pipeline pump.

6. The formaldehyde production process unit according to claim 1, characterized in that: the oxidation device comprises a silver catalyst layer, a tank body, a cooling pipe vertically arranged in the tank body, and a pipe plate and a seal head which are arranged at two ends of the cooling pipe, wherein a feed inlet is arranged on the side surface of the lower part of the tank body, a first sealed chamber and a second sealed chamber are respectively arranged on the outer wall of the tank body corresponding to the feed inlet and below the feed inlet in a surrounding manner, the silver catalyst layer comprises at least two connected first silver catalytic net layers and second silver catalytic net layers, and the first silver catalytic net layers and the second silver catalytic net layers are respectively arranged in the first sealed chamber and the second sealed chamber; the silver catalyst layer is also provided with a lifting device.

7. The formaldehyde production process unit according to claim 6, characterized in that: the second closed chamber is filled with inert gas, and the air pressure of the second closed chamber is higher than that of the feeding hole.