JPH10251410A - Gas circulation feeder for solid phase polymerization apparatus and method for washing gas heat exchanger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus and method for efficiently washing stains on the heat transfer surface of a heat exchanger provided in an apparatus for circulating and feeding a gas into a hot gas stream flow type continuous solid phase polymn. apparatus which is used in solid phase polymn. of a thermoplastic resin, such as polyamide or polyester. SOLUTION: This gas circulation feed apparatus comprises: a gas circulation feed passage for circulating and feeding an inert gas into a continuous solid phase polymn. apparatus for a particulate thermoplastic resin; and a gas heat exchanger provided in the course of the passage, wherein a washing water feed port 4 and a steam feed port 6 are provided at the bottom of the gas heat exchanger 1, a washing water outlet 5 for overflow is provided at the top of the gas heat exchanger 1, and a drain discharge port 7 is provided at the lowermost end. In washing the interior of the gas heat exchanger, feed of washing water from the washing water feed port 4, feed of steam from the steam feed port 6, and discharge of overflow water from the washing water discharge port 5 are simultaneously carried out to wash the internal wall surface with hot water of 70 to 95 deg.C. Thereafter, hot water for washing is discharged from the drain discharge port 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention is useful as a device for circulating and supplying an inert gas to a hot-air flowing continuous solid-state polymerization apparatus used for continuous solid-state polymerization of thermoplastic resins such as polyamide and polyester. Device. More specifically, the present invention relates to an apparatus and a method for efficiently cleaning and removing dirt on an internal heat transfer surface of a heat exchanger in a flow passage of the gas circulation supply device.

[0002]

2. Description of the Related Art Generally, solid-phase polymerization of a thermoplastic resin (eg, polyamide or polyester) is performed by heating a chip obtained by a melt polycondensation reaction in an atmosphere of an inert gas at a temperature lower than a melting point. Thus, the polycondensation reaction further proceeds, and a polymer chip having a high degree of polymerization is obtained. At this time, the inert gas is heated and supplied to a temperature suitable for the solid-state polymerization reaction in advance, and the chip layer is aerated.

Along with this solid-state polymerization reaction, a reaction by-product,
For example, water is generated in polyamide and water and glycols are generated in polyester, and these reaction by-products are discharged out of the system together with the inert gas used for the solid-phase polymerization. Since an inert gas is generally expensive, a method of purifying the exhausted inert gas and supplying it again is usually employed.

In the exhaust gas, besides reaction by-products, monomers and oligomers generated in a reaction equilibrium, for example, dimers and trimers are also contained. In addition, for example, in polyethylene terephthalate, diethylene glycol and nylon 66 are used. In the exhaust gas, by-products such as hexamethylenediamine and adipic acid are also entrained. Of course, the fine powder of the polymer contained in the chip is also discharged together with the gas.

[0005] In this gas circulation circuit, exhaust gas is first cooled by a gas cooler, and then by-products contained in the gas are removed by purification. As the purification means, ordinary methods such as a method of condensing and removing by-products and a method of adsorbing and removing by passing through a column filled with an adsorbent are employed. Thereafter, the mixture is reheated to a predetermined temperature by a gas heater and fed into a chip layer to be solid-phase polymerized.

[0006] As described above, a gas cooler or a gas heater (hereinafter, generically referred to as a gas heat exchanger or a heat exchanger) installed in the gas circulation circuit contains reaction by-products, monomers and oligomers, and the like. Since the exhaust gas containing the gas passes through, contamination due to scale adhesion progresses with time on the internal heat transfer surface, often leading to loss of the heat exchange function. Particularly in a gas cooler, the contamination is remarkable, so that cleaning of the heat transfer surface is an indispensable operation even during daily operation.

Conventionally, as a method of cleaning a contaminated heat transfer surface, a gas purge method in which high-pressure gas is blown onto the heat transfer surface, a water washing method using jet water, and the like have been used.

[0008]

However, the conventional cleaning method has the following problems, and a more efficient cleaning means has been desired.

The scale to be adhered has tackiness because it contains monomer and oligomer components as well as powders. Therefore, the adhered scale can hardly be removed by the high pressure gas purge cleaning method. In addition, in the water washing method, the heat transfer surface cannot be completely cleaned due to poor solubility of the sticky substance.
In addition, since a multi-tube heat exchanger having fins of aluminum or the like is generally used as the heat exchanger, it is extremely difficult to clean the space between the fins.

[0010] Due to such a problem, the heat exchanger once contaminated cannot be restored to the same heat exchange capacity as that of a new device even after being cleaned. Therefore, when designing a new heat exchanger, it is necessary to overestimate the dirt coefficient, and the equipment cost of the heat exchanger becomes high.

In order to completely clean the contaminated heat exchanger, there is a method of disassembling the contaminated heat exchanger during use and brushing the heat transfer surface for cleaning. It is labor intensive and difficult to implement industrially.

Accordingly, the present invention solves the above-mentioned problems of the prior art, and provides a hot-air flowing continuous solid-state polymerization apparatus used for solid-state polymerization of a thermoplastic resin such as polyamide or polyester. A main object of the present invention is to provide an apparatus and a method for efficiently cleaning dirt on a heat transfer surface of a heat exchanger provided in an apparatus for circulating and supplying gas.

[0013]

In order to achieve the above object, a gas circulating supply apparatus for a solid-state polymerization apparatus according to the present invention comprises a gas circulating supply flow for circulating and supplying an inert gas to the solid-state polymerization apparatus. In a gas circulation supply device having a passage and a gas heat exchanger provided in the middle of the passage, a washing water supply port and a steam supply port are provided at a lower portion of the gas heat exchanger, and a washing water for overflow is provided at an upper portion. The outlet is further provided with a drain outlet at the lowermost end.

Further, the method of cleaning the inside of the gas heat exchanger is that the supply of cleaning water from the cleaning water supply port, the supply of steam from the steam supply port, and the discharge of overflow from the cleaning water outlet are performed simultaneously. The inner wall surface is washed with hot water at 70 to 95 ° C., and thereafter, the washing hot water is discharged from the drain liquid outlet.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An apparatus according to the present invention will be described with reference to FIGS. FIG. 2 is a flowchart showing a continuous solid-state polymerization apparatus and a gas circulation / supply apparatus attached thereto, and FIG. 1 is a schematic longitudinal sectional view showing one embodiment of a heat exchanger used in the apparatus.

A thermoplastic resin, particularly a polyester or polyamide chip, is supplied to the solid-state polymerization tower 20 while being measured by a chip-input rotary valve 22 as shown by a flow of an arrow in FIG. , And is discharged by a chip discharge rotary valve 27. An inert gas heated to a temperature necessary and sufficient for solid-state polymerization is supplied from the lower part into the inside of the solid-state polymerization tower. The inert gas comes into countercurrent contact with the chips in the tower, and the chips obtain heat from the inert gas to perform a solid state polymerization reaction.
Depending on the flow rate of the supplied gas, the chip and the gas may simply be brought into countercurrent contact or may be fluidized in the column.

The inert gas supplied into the tower is blower 26
And heated by the gas heater 25. And when it comes into contact with the chip in the solid-state polymerization tower 20,
Components generated by solid-state polymerization, polymer powder, oligomer components, and the like are taken into the gas, and are discharged from the upper portion of the solid-state polymerization tower 20 as exhaust gas containing these components. After the discharged gas is once cooled by the gas cooler 23, the adsorption tower 24 adsorbs and removes impurities such as moisture and substances by-produced by the solid-state polymerization reaction. Thereafter, the inert gas is compressed by the blower 26 together with the gas replenished from the inert gas supply port 28, heated to a desired temperature by the gas heater 25, and supplied again to the solid-state polymerization tower.

The reason why the inert gas is used as the gas used in the solid-state polymerization reaction is to prevent the resin added from reacting with oxygen due to the heat applied during the solid-state polymerization to deteriorate the resin. Industrially, nitrogen gas is most widely used.

Typical equipment capable of efficiently cleaning the internal heat transfer surface of a gas heat exchanger such as a gas cooler 23 or a gas heater 25 attached to such a continuous solid-state polymerization apparatus. A typical example is the heat exchanger of FIG. In FIG. 1, reference numeral 1 denotes a gas heat exchanger (main body), which corresponds to a gas cooler or a gas heater in the apparatus of FIG. The circulating inert gas is introduced into the heat exchanger 1 from the inert gas inlet 2, and a cooling or heating operation (heat exchange) is applied to the surface of the heat transfer unit 12. The gas may flow either upward or downward in the vertical heat exchanger, and the gas supply and outlet may be horizontal as in a horizontal heat exchanger. After the heat exchange, the gas is discharged from the inert gas outlet 3.

As the heat transfer section 12, a multi-tube heat exchanger, a multi-tube heat exchanger with fin tubes, a plate heat exchanger, or the like is used. In such a gas heat exchanger, a heat medium or a refrigerant is supplied from an inlet 10 of the heat medium / refrigerant and discharged from an outlet 11 of the heat medium / refrigerant.

In this heat exchanger, a washing water supply port 4 and a steam supply port 6 are provided at a lower part, a washing water outlet 5 for overflow is provided at an upper part, and a drain liquid discharge port 7 is provided at a lowermost part. Each is arranged. In addition, watering nozzle 8
Is preferably provided. This gas heat exchanger functions as a gas heater when a heat medium is supplied to the heat transfer section, and functions as a gas cooler when a refrigerant is supplied.

For cleaning the inside of the heat exchanger, the cleaning water is supplied from the cleaning water supply port 4 and the steam is supplied from the steam supply port 6 at the same time. Simultaneously, the inner wall surface is washed with warm water of 70 to 95 ° C., and after the washing is completed,
The cleaning is performed by discharging hot water for cleaning from the drain liquid discharge port 7.

As a specific cleaning procedure, first, the valves near the inlet 2 and the outlet 3 of the inert gas are closed to stop the flow of the inert gas. Further, the valves near the heat medium / refrigerant inlet 10 and the outlet 11 are closed to stop the flow of the heat medium / refrigerant. Since there is no heat medium / refrigerant remaining in the heat exchanger, an appropriate temperature can be obtained quickly during washing, a discharge valve (not shown) for supplying the heat medium / refrigerant or providing a residue at the outlet should be provided. Is preferred. Thereafter, the valve (the overflow valve 13) in the immediate vicinity of the washing water outlet 5 is opened to allow overflow. Next, the valve in the immediate vicinity of the washing water supply port 4 is opened to flow water into the heat exchanger 1. A see-through window or a funnel is provided in the middle of the pipe leading to the wash water outlet 5, and the level of the wash water in the heat exchanger is observed. Introduce steam into the exchanger.

The supply amount of cleaning water and / or the supply amount of steam are adjusted while measuring the overflow temperature so that the inner wall temperature becomes 70 to 95 ° C. The ratio of these fluids may be optimized according to the degree of contamination of the heat transfer surface. When the dirt is severe, it is preferable to increase the water flow. At this time, the steam amount is also adjusted to maintain the overflow temperature at a predetermined value. When the dirt is not severe, the amount of water passing may be an amount that can maintain the overflow.
These operations may be performed manually or automatically according to a program set by employing an automatic valve including a temperature controller.

The washing temperature is preferably from 70 to 95 ° C. 70 ° C. or higher is preferable from the viewpoint of the cleaning effect, and there is no particular problem as to the cleaning effect even when the temperature exceeds 95 ° C. However, from the viewpoint of operational safety, the cleaning water inside the heat exchanger does not boil. It is preferable that the temperature is specifically about 95 ° C. at the highest. In such a cleaning method, a large cleaning effect can be exhibited by utilizing a water hammer phenomenon that occurs when steam directly contacts water. In this water hammer phenomenon, water vapor is directly
This is a phenomenon in which water vibrates due to condensation of water vapor that occurs rapidly when it comes into contact with water. The generated vibration oscillates the hot water passing through the heat transfer surface, and exerts a great effect in detaching the scale attached to the heat transfer surface. For this reason, it is preferable not to provide a muffler or the like in the steam supply port 6 in order to enhance the cleaning effect.

Since the overflowed washing water contains the above-mentioned organic substances and the like, it is sent to an appropriate wastewater treatment facility for treatment. When the overflowing cleaning water becomes clean, stop introducing steam. When drain liquid is discharged, a large amount of drain liquid is temporarily discharged.If the temperature of the discharged drain liquid is high, it is dangerous in the work environment and the load on the wastewater treatment equipment will be excessive. The passage of water is continued until the water temperature inside the exchanger reaches a temperature at which the water can be drained, usually about 60 ° C. or less. Thereafter, the valve immediately adjacent to the cleaning water supply port 4 is closed, and the cleaning hot water (drain liquid) inside the heat exchanger is discharged from the drain liquid discharge port 7.

When the cleaning is completed, a method is set in advance to determine whether the cleaning is sufficient or not, by setting a necessary hot water passage time in a heat transfer surface inspection or the like, and managing the hot water passage time in a normal operation. Is preferable for work management.

In the cleaning operation of the heat exchanger, finally, the hot water for cleaning inside the heat exchanger is discharged from the drain liquid discharge port 7, and the entire scale separated from the heat transfer surface is completely drained by one drainage. Since it is difficult to flow out together with the washing water, it is preferable to perform so-called rinsing. In order to carry out the rinsing efficiently and without impairing the workability, a sprinkling nozzle 8 is provided in the upper part of the heat exchanger, and after the washing hot water is discharged, new washing water is supplied from the sprinkling nozzle 8. It is preferable to rinse the inside by sprinkling water and discharging the water from the drain outlet.

The watering nozzle 8 may be provided above the heat transfer surface as shown in FIG. The shape of the watering nozzle 8 may be a nozzle having pores or a nozzle specially designed for watering. It is preferable to arrange a plurality of watering nozzles 8 so that rinsing water can be poured uniformly on the heat transfer surface. In addition, the disposition position may be the most appropriate position depending on the shape of the heat exchanger, but is preferably a position where water can be sprinkled on the entire surface of the heat transfer section and the container section storing the heat transfer section.

The rinsing by spraying new washing water may be used as a measure of completion when the discharged liquid from the drain liquid outlet 7 becomes clear. When the rinsing is completed, the rinsing water supply valve 14 is closed to stop watering. Then, immediately after the drain liquid has been discharged, the drain valve is left closed without closing, and the inside of the heat exchanger is naturally dried. Thus, the cleaning of the inside of the gas heat exchanger (particularly, its heat transfer surface) is completed.

After drying the inside of the heat exchanger, the inside of the heat exchanger is replaced with an inert gas. For this purpose, it is preferable to provide a replacement inert gas supply and discharge valve in a part of the heat exchanger body or the connected inert gas pipe. In particular, it is preferable to provide an oxygen concentration meter for measuring the oxygen concentration in the exhaust gas on the side of the discharge valve in order to accurately determine the completion of the replacement.

Further, in the present invention, it is preferable to arrange a plurality of gas heat exchangers having substantially the same function in parallel in the gas circulation supply flow path. In this case, by switching to a spare heat exchanger, it is possible to wash the inside of the heat exchanger without interrupting solid-state polymerization in the continuous solid-state polymerization apparatus.

That is, when the heat transfer surface of the heat exchanger becomes remarkably contaminated and the time for cleaning is reached, the heat exchanger is switched to a spare heat exchanger among a plurality of heat exchangers arranged in parallel. After the cleaning, the inside of the contaminated heat exchanger may be washed, which is an excellent method for industrial production in that the washing can be performed while the production is continued.

[0034]

【Example】

[Example 1] Solid phase polymerization of polyethylene terephthalate was carried out using the solid phase polymerization apparatus shown in FIG. That is, a polymer chip having an intrinsic viscosity (IV) of 0.70 obtained by liquid-phase polymerization is continuously supplied to the solid-state polymerization tower 20 at a rate of 15 tons / day, Removed at flow rate. 220 g from the gas blowing part at the bottom of the solid-state polymerization tower 20
A nitrogen gas heated to 0 ° C. is supplied to bring the chip into countercurrent contact with the flowing chip, and the IV value of the polymer chip is increased to 1.20 through a residence time of 15 hours, and the solid-phase polymerized chip is continuously cooled. I got it.

The nitrogen gas is subjected to a solid-state polymerization reaction in the solid-state polymerization tower 20 and then discharged from the upper part of the tower.
Then, the mixture is cooled to 25 ° C. in an adsorption column 24 filled with synthetic zeolite, and impurities contained in the gas, that is, water and ethylene glycol generated by a solid phase polymerization reaction are adsorbed and removed and purified. Was. The purified nitrogen gas is compressed by a blower 26 and
The mixture is heated to ℃ and is circulated to the solid-state polymerization tower 20 again.

When the apparatus was operated continuously for 14 days, the temperature at the outlet of the gas cooler 23 could not be maintained at 25 ° C., so it was judged that dirt on the heat transfer surface of the cooler 23 had accumulated. Spare gas coolers 23 'arranged in parallel
Switched to.

The gas coolers 23 and 23 'have the structure shown in FIG. 1, and the heat transfer section 12 is provided with an aluminum fin type heat transfer tube. After the gas line was switched and the refrigerant (cooling water) was drained, the gas cooler 23 which had been continuously used was disassembled and inspected. The powder adhered to one side. The gas cooler was assembled again, the upper overflow valve 13 was opened, and the washing water was supplied from the lower part. After confirming that the washing water overflowed from the overflow pipe, saturated steam having a supply source pressure of 100 KPa was supplied. When the water temperature at the washing water outlet 5 rose to 90 ° C., the opening of the steam supply valve was fixed. The water was kept flowing for 2 hours while maintaining the state. At first, the overflowing washing water was cloudy. After 2 hours, it was confirmed that the overflow became clear. Therefore, the supply of water vapor was stopped, and only the washing water was continuously flown. When the water temperature at the overflow port dropped to 60 ° C., the supply of the washing water was stopped, and the drain liquid discharge valve 15 was opened to open the drain liquid in the heat exchanger. Was discharged.

Thereafter, the rinsing water supply valve 14 communicating with the water spray nozzle 8 disposed above the heat transfer tube was opened to spray the washing water from above, thereby rinsing the inside of the gas cooler. At first, white turbid matter was observed in the drain water from the drain liquid discharge port 7, but after a few minutes, the waste water became clear, so the rinsing was completed.

When the upper lid of the gas cooler was opened and the inside was inspected, no substance adhered to the surface of the heat transfer surface and the inner wall was found, and it was clean. It was restored again, the valve around the gas cooler was closed, and nitrogen gas was supplied to the inside. On the other hand, nitrogen gas was discharged to replace the inside of the cooler with nitrogen.

Comparative Example 1 Solid-state polymerization of polyethylene terephthalate was carried out in the same manner as in Example 1, and the heat exchange capacity was reduced. Therefore, the gas cooler was replaced with a spare gas cooler installed in parallel. The state of contamination inside the gas cooler used was the same as in Example 1.

The gas cooler was disassembled, and a pressure of 400 KPa was jetted to blow off the scale. However, the adhered substance hardly fell off due to the stickiness. Next, the inside was washed with jet water using room temperature water, but the deposits were slightly removed and the inner surface was not cleaned.

Example 2 Solid state polymerization of polyhexamethylene adipamide (nylon 66) was performed using the solid state polymerization apparatus shown in FIG. That is, a polymer chip having a relative viscosity of sulfuric acid (ηr) of 2.80 obtained by liquid-phase polymerization was continuously added to 1
The mixture was supplied to the solid-state polymerization tower 20 at an amount of 5 tons / day, and was taken out from the lower part of the solid-state polymerization tower 20 at the same flow rate. Solid phase polymerization tower 20
A nitrogen gas heated to 160 ° C. is supplied from a gas blowing part at a lower part of
After a retention time of 時間, the ηr value of the polymer chip was 3.60.
And solid-phase polymerized chips were continuously obtained.

Nitrogen gas is discharged from the upper part of the solid-state polymerization tower 20 after being subjected to a solid-state polymerization reaction in the solid-state polymerization tower 20,
3 and then cooled to 25 ° C., and then, in an adsorption column 24 filled with activated alumina, impurities contained in the gas, that is,
Water and the like generated by the solid-state polymerization reaction were adsorbed and removed and purified. The purified nitrogen gas is compressed by the blower 26, heated to 160 ° C. by the gas heater 25, and circulated and supplied to the solid-state polymerization tower 20 again.

When the apparatus was operated continuously for 30 days, the temperature at the outlet of the gas cooler 23 could not be maintained at 25 ° C., so it was judged that dirt on the heat transfer surface of the cooler 23 had accumulated. Spare gas coolers 23 'arranged in parallel
Switched to.

The gas coolers 23 and 23 'used in Example 1
Is the same as After switching the gas line to drain the refrigerant (cooling water) and disassembling and inspecting the gas cooler that had been used until then, the polymer fine powder together with the adhesive substance on the surface of the heat transfer tube and the inner wall of the gas cooler body Was attached to one side. When the gas cooler was reassembled and the inside was cleaned in the same manner as in Example 1, the substances adhering to the surface and the inner wall of the heat transfer tube were separated and cleaned.

[Comparative Example 2] Solid-state polymerization of polyhexamethylene adipamide (nylon 66) was carried out in the same manner as in Example 2, and the heat exchange capacity was reduced. . The state of contamination inside the gas cooler used was the same as in Example 2.

The gas cooler was disassembled, and the inside was cleaned by the same means as in Comparative Example 1. However, as in Comparative Example 1, the inner surface was not cleaned.

[0048]

According to the present invention, according to the present invention, there is provided a hot air circulation type solid-state polymerization apparatus used for solid-state polymerization of a thermoplastic resin such as polyamide or polyester. Dirt on the heat transfer surface of the exchanger can be efficiently cleaned.

[Brief description of the drawings]

FIG. 1 is a flow chart showing a gas circulation supply device of the present invention and a continuous solid-state polymerization device provided with the same.

FIG. 2 is a schematic longitudinal sectional view showing one embodiment of a heat exchanger used in the gas circulation supply device of FIG. 1 of the present invention.

[Description of Signs] 1: Gas heat exchanger (gas cooler or gas heater),
4: Wash water supply port, 5: Wash water outlet, 6: Steam supply port, 7: Drain liquid discharge port, 8: Spray nozzle, 2
0: solid-state polymerization apparatus, 21: gas circulation supply channel

Claims (7)

[Claims] 1. A gas circulation supply device having a gas circulation supply flow path for circulating and supplying an inert gas to a solid-state polymerization apparatus, and a gas heat exchanger provided in the middle of the flow path, A solid phase characterized in that a washing water supply port and a steam supply port are provided at a lower portion of the heat exchanger, a washing water outlet for overflow is provided at an upper portion, and a drain liquid outlet is provided at a lowermost portion. Gas circulation supply device for polymerization equipment. 2. The method according to claim 1, wherein the gas heat exchanger is a gas cooler and / or a gas cooler.
The gas circulation supply device for a solid-state polymerization device according to claim 1, wherein the gas circulation supply device is a gas heater. 3. The solid-state polymerization apparatus according to claim 1, wherein a plurality of gas heat exchangers having substantially the same function are arranged in parallel in the gas circulation supply flow path. Gas circulation supply device. 4. The gas heat exchanger according to claim 1, further comprising a watering nozzle at an upper part in the gas heat exchanger.
4. The gas circulation supply device for a solid-state polymerization device according to 2 or 3. 5. When cleaning the inside of the gas heat exchanger according to claim 1, supply of cleaning water from a cleaning water supply port, supply of steam from a steam supply port, and overflow of the cleaning water outlet. The inner wall surface is 70-95 ° C by discharging simultaneously.
A method for cleaning a gas heat exchanger, comprising: cleaning with hot water, followed by discharging hot water for cleaning from a drain liquid outlet. 6. A method for cleaning a gas heat exchanger according to claim 3, wherein when cleaning the inside of the gas heat exchanger, the plurality of gas heat exchangers arranged in parallel are cleaned while switching. . 7. The gas heat exchanger according to claim 5, wherein after the washing hot water is discharged, the washing water is sprinkled from an upper spray nozzle in the gas heat exchanger to perform rinsing. Cleaning method.