JPH06301A - Spray dryer for solvent recovery - Google Patents

Abstract

PURPOSE:To recover organic solvent and to dry slurry powder with low cost equipment and good energy efficiency by cooling circulated gas after spray drying to the specified temp. to condense and recover solvent and next absorbing solvent into water with a water scrubber to recover it. CONSTITUTION:Organic vapor from circulated gas after product powder is recovered is recovered with the 1st recovery device 10 where the circulated gas is cooled to 10-50 deg.C to condense and recover organic vapor included in the circulated gas and the 2nd recovery device 12 where the circulated gas passed through the 1st recovery device 10 and water are brought into contact with each other in a water scrubber 20 to absorb and recover water soluble organic solvent included in the circulated gas into water. As a result, drying granulation by spray drying is performed with low cost equipment and at low running cost to be economically profitable.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a spray dryer (closed cycle spray dryer) for spray-drying a slurry containing an organic solvent as a dispersion medium by a circulating gas, after being subjected to spray-drying with good energy efficiency. The present invention relates to a solvent recovery spray dryer capable of recovering the organic solvent contained in the circulating gas and spray drying with the circulating gas after recovering the organic solvent.

[0002]

2. Description of the Related Art In a spray dryer (closed cycle spray dryer) in which a non-combustible gas such as nitrogen gas is used as a circulating gas, and spray drying is performed by this circulating gas to perform dry granulation, the product to be granulated is In the case of powder that is easily oxidized, such as metal powder for hard cutting tools,
An organic solvent such as ethyl alcohol is used as a dispersion medium for the slurry.

FIG. 2 conceptually shows such a spray dryer. In the example shown in FIG. 2, the slurry A supplied to the atomizer 104 by the slurry pump 102 is heated to about 150 ° C. by the heating device 106 and sent to the drying chamber 108. The powder that is sprayed into the atmosphere is dried and granulated, and collected from the lower part of the drying chamber 108. On the other hand, the circulating gas is sent to the cyclone 110, and the cyclone 11
At 0, the product powder sent with the circulating gas is recovered, and the bag filter 112 further recovers the product powder contained in the circulating gas.

Since the circulating gas after the product powder is recovered contains a large amount of the organic solvent which is the dispersion medium of the slurry, it is necessary to remove the organic solvent to the extent that the drying operation is possible.
Therefore, the circulating gas is (direct contact) solvent recovery device 114.
After the organic solvent contained in is removed, it is sent to the circulating gas blower 116, heated again by the heating device 106, and subjected to spray drying.

Conventionally, as an organic solvent recovery device in such a spray dryer, a solvent recovery device by direct contact cooling as shown in FIG. 2 and a solvent recovery device by indirect cooling as shown in FIG. 3 described later. And are commonly used.

The direct contact solvent recovery device 114 uses a so-called scrubber or the like to bring the cooled organic solvent into direct contact with the circulating gas to remove and recover the organic solvent from the circulating gas. Specifically, as shown in FIG. 2, the cooled organic solvent is circulated through the system including the scrubber 122 by the cooling means including the cooling device 118, the heat exchanger 120, and the circulation pump 121, and the upper part of the scrubber 122. It is sprayed into the scrubber 122 from the spray nozzle.
The circulating gas that has passed through the bag filter 112 is introduced into the scrubber 122 and is cooled by contact with the cooled and atomized organic solvent. As a result, the organic solvent vapor contained in the circulating gas is condensed and mixed with the circulating organic solvent in the scrubber 122, and is recovered in the solvent recovery tank 124.

On the other hand, as shown in FIG. 3, the solvent recovery device by indirect cooling basically has a cooling pipe 126a inside.
And a heat exchanger 126 having a large number of
Cooling means 128 having a refrigerator 130 and a circulation pump 132 for supplying and cooling the refrigerant to (the cooling pipe 126a)
And a solvent recovery tank 124. In the solvent recovery apparatus shown in FIG. 3, the circulating gas that has passed through the bag filter 112 is indirectly cooled by the refrigerant introduced into the heat exchanger 126 and supplied to the heat exchanger 126. As a result, the organic solvent contained in the circulating gas is condensed and removed from the circulating gas, and is recovered downward as a liquid.

[0008]

By the way, the above-mentioned FIG.
And in the solvent recovery apparatus shown in FIG. 3, in order to remove the organic solvent (gas) from the circulating gas to the extent that good powder drying is possible and to reuse the circulating gas for the spray drying operation in the drying chamber 108, However, it is necessary to cool the circulating gas to about 10 ° C., which causes various problems economically.

Product powder is collected and bag filter 11
Circulating gas supplied to the solvent recovery device from 2 is usually 90
The temperature is around ℃. In order to cool this circulating gas to about 10 ° C., in the solvent recovery apparatus by direct cooling shown in FIG. 2, the organic solvent supplied to the scrubber 122 is set to about 5 ° C., while the solvent by indirect cooling shown in FIG. 3 is used. In the recovery device, it is necessary to cool the refrigerant supplied to the heat exchanger 126 to about -2 ° C. Therefore, a large amount of energy is required to cool the circulating organic solvent and refrigerant. Moreover, a brine cooler and a refrigerator using a high-pressure compressor having a cooling capacity for executing this are expensive as mechanical equipment.

In order to use the circulating gas from which the organic solvent has been recovered for spray drying again, the heating device 1 is used as described above.
It is necessary to heat the circulating gas to about 150 ° C. by 06, but a large amount of energy is required to heat the circulating gas cooled to 10 ° C. to about 150 ° C., and the energy efficiency is poor.

An object of the present invention is to solve the above-mentioned problems of the prior art. When spray-drying a slurry having an organic solvent as a dispersion medium, it is possible to reduce the cost of the organic solvent with inexpensive equipment and good energy efficiency. It is an object of the present invention to provide a solvent recovery spray dryer capable of performing recovery and powder drying of a slurry.

[0012]

In order to achieve the above object, the present invention is a spray dryer for spray-drying a slurry containing a water-soluble organic solvent as a dispersion medium with a circulating gas to obtain a dry powder. Circulating gas after spray drying 10-5
A first recovery device that condenses and recovers the water-soluble organic solvent contained in the circulating gas by cooling to 0 ° C. and a circulating gas that has passed through the first recovery device by a water scrubber are brought into contact with each other to circulate. There is provided a solvent recovery spray dryer, comprising: a second recovery device that absorbs and recovers a water-soluble organic solvent contained in gas into water.

Another aspect of the present invention is a distillation apparatus for recovering the water-soluble organic solvent by distilling water having absorbed the water-soluble organic solvent in the second recovery apparatus in the solvent recovery spray dryer. Provide an accompanying solvent recovery spray dryer.

[0014]

The solvent recovery spray dryer of the present invention comprises:
A slurry containing a water-soluble organic solvent as a dispersion medium is spray-dried with a circulating gas, and the organic solvent is recovered from the circulating gas after the product powder is recovered.
The first recovery device that condenses and recovers the organic solvent contained in the circulating gas by cooling to 50 ° C. is brought into contact with the circulating gas that has passed through the first recovery device by the water scrubber, and is contained in the circulating gas. A second recovery device that absorbs and recovers the water-soluble organic solvent in water is used.

In the solvent recovery spray dryer of the present invention having the above structure, since the first solvent recovery device only has to cool the circulating gas to 10 to 50 ° C., in either case of indirect cooling or direct cooling, The coolant for cooling the circulating gas may have a temperature of about 20 to 30 ° C. Also, in the second recovery device that recovers by absorbing the organic solvent contained in the circulating gas with water using the water scrubber, since the water for absorbing the organic solvent may be kept at a water temperature of around 35 ° C, Cooling water of about 30 ° C. or the like is sufficient as the cooling medium for cooling this, and the cooling medium of about 30 ° C. can be easily obtained by a chiller using atmospheric ventilation and is economical.

In other words, the solvent recovery spray dryer of the present invention does not need to cool the refrigerant (or the organic solvent) to a low temperature as in the conventional apparatus, so that the energy required therefor can be greatly reduced. In addition, since a large-sized and high-performance cooling device is not required, it is possible to use an inexpensive mechanical device. Moreover, in the solvent recovery spray dryer of the present invention, as described above, the refrigerant for cooling (absorbing) the circulating gas is about 20 to 30 ° C. in both the first recovery device and the second recovery device. The temperature of the circulating gas after being collected is the same as that of the cooling water in winter.
If the temperature is about 30 ° C. in summer, the temperature is about 20 to 40 ° C. Therefore, the thermal energy for reheating the circulating gas for performing spray drying can also be significantly reduced as compared with the conventional device. Therefore, according to such a solvent recovery spray dryer of the present invention, it is possible to perform dry granulation by spray drying at low running cost with inexpensive mechanical equipment, which is extremely economically advantageous.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The solvent recovery spray dryer of the present invention will now be described in detail with reference to the preferred embodiments shown in the accompanying drawings.

FIG. 1 conceptually shows the solvent recovery spray dryer of the present invention. The solvent recovery spray dryer of the present invention is different from a closed cycle type solvent recovery spray dryer that uses a conventional circulating gas in that the solvent recovery device that recovers the organic solvent that is the dispersion medium of the slurry from the circulating gas is different. Yes, the spray drying of the slurry, product recovery, reheating of the circulating gas for spray drying, etc. are basically the same as the conventional one shown in FIG.
FIG. 1 mainly shows a solvent recovery device, and the same members are denoted by the same reference numerals. Hereinafter, the solvent recovery device will be mainly described.

The product powder targeted by the solvent recovery spray dryer of the present invention is not particularly limited.
Ion exchange resin, insecticide, pigment, polymer compound, dye,
It can be used for pharmaceuticals, powder coatings, foods, fine ceramics, etc., which have been granulated and dried by a spray dryer. Further, as the dispersion medium of the slurry which is the aspect of the solvent recovery spray dryer, any known one can be used as long as it is a water-soluble organic solvent, specifically, ethyl alcohol, methyl alcohol, acetone, trioxane, dichloromethane. Preferable examples are isopropyl alcohol and the like.

In the solvent recovery spray dryer of the present invention shown in FIG. 1, the solvent recovery device is the first recovery device 10,
Second recovery device 12, cooling device 14 for supplying cooling water as a refrigerant to both recovery devices, distillation column 16, and solvent recovery tank 1
It is composed of 8.

In the solvent recovery spray dryer of the present invention shown in FIG. 1, a drying chamber 108 and a cyclone 110 are provided.
The circulating gas from which the product powder has been recovered (see FIG. 2) and the bag filter 112 is introduced into the first recovery device 10. The first recovery device 10 circulates the circulating gas at about 10 to 50 ° C, preferably 20 to 50 ° C, more preferably 20 to 3 ° C.
By cooling to 0 ° C., the organic solvent vapor contained in the circulating gas is condensed to recover the organic solvent.

In the illustrated example, the first recovery device 10 is
A so-called heat exchanger (condenser), which is composed of a tubular body in which a large number of pipes 10a through which cold water as a refrigerant passes are arranged.
That is, the circulating gas is cooled by indirect cooling. In the first recovery device 10 (the pipe 10a thereof) of the illustrated example, a cooler 14 is provided.
Cooling water of 30 ° C. or less is supplied, and the circulating gas of about 90 ° C. introduced from the bag filter 112 comes into contact with the pipe 10a through which the cold water passes, and by the internal atmosphere cooled by the pipe 10a, 1 Within the recovery device 10, it is cooled down to about 40 ° C. Accordingly, the organic solvent having a saturation point or higher contained in the circulating gas is condensed and separated from the circulating gas, drops into droplets, and is collected in the lower solvent reservoir. The organic solvent recovered in the solvent reservoir by the first recovery device 10 is appropriately sent to the solvent recovery tank 18. The cooling water that has passed through the pipe 10a of the first recovery device 10 is returned to the cooler 14 again as shown in FIG. 1 and cooled.

The temperature of the refrigerant supplied to the first recovery device is
Depending on the configuration of the first recovery device (capacity of the heat exchanger), the temperature and type of the circulating gas introduced into the first recovery device, and the type of the organic solvent to be recovered, the circulating gas is kept at 10 to 50 ° C.
The temperature at which the water can be cooled may be appropriately determined and is not particularly limited, but the load on the distillation column 16 is reduced when the temperature is made as low as possible with cooling water.

In the present invention, the first recovery device 10
Is not limited to indirect cooling as described above,
Direct cooling using a scrubber using the same organic solvent as the organic solvent to be recovered may be used.

The circulating gas discharged from the first recovery device 10 is then introduced into the second recovery device 12. The second recovery device 12 removes and recovers the organic solvent remaining in the circulating gas by absorbing the organic solvent into water using the water scrubber, and basically absorbs the water scrubber 20 and the organic solvent. A circulating pump 22 that circulates the circulating water in a system including the water scrubber 20, and a heat exchanger 24 that cools the circulated water.

The water scrubber 20 has a large number of water injection nozzles in the upper part and a water storage part for storing water in the lower part, and the circulation pump 22 transports the water from the lower part of the water storage part to the water injection nozzles. The water is ejected in the form of water droplets or water film, and the water is circulated from the lower part of the water storage portion to the water injection nozzle. Further, the cooling water is supplied from the cooling device 14 to the heat exchanger 24 in the water circulation path, as in the case of the first recovery device 10 described above, and is circulated between the lower part of the water storage section and the water injection nozzle. Cool the water below 35 ° C.

The water ejected from the water injection nozzle comes into contact with the circulating gas introduced into the second recovery device 12 (water scrubber 20) to absorb and recover the organic solvent contained in the circulating gas. The organic solvent absorbed in the water of the water scrubber 20 is separated from water by the distillation column 16 described later and recovered. On the other hand, the circulating gas from which the organic solvent has been removed is sent to the heating device 106 by the circulating gas blower 116, reheated, and provided for spray drying. Where the second
The temperature of the circulating gas introduced into the recovery device 12 is 20 to 40 ° C. as described above, and the water in the water scrubber 20 that comes into contact with the circulating gas is 35 ° C. or lower, so the second recovery device 12 The temperature of the circulating gas discharged from 20 to 40
It is about ℃.

The solvent recovery spray dryer of the present invention has the above-mentioned structure, that is, the first recovery device 10 for cooling the circulating gas to 10 to 50 ° C. for recovering the organic solvent from the circulating gas, and the organic solvent is absorbed by the water scrubber. By using the second recovery device, the energy for cooling the circulating gas and the cost of the cooling device can be reduced. Further, since the circulating gas from which the solvent has been removed has a temperature of about 20 to 40 ° C., the thermal energy for reheating the circulating gas for spray drying can be significantly reduced as compared with the conventional device. it can.

Water circulated in the second recovery device 12,
That is, the temperature of the water used for the water scrubber is not particularly limited, and may be a temperature slightly lower than that depending on the temperature of the circulating gas introduced. Therefore, the cooling of the water of the water scrubber is performed by the first recovery device 10 as in the example shown in FIG.
It is preferable to use the cooling water used in the above together. Of course, an independent cooling device may be used for cooling the water of the water scrubber.

The water in the water scrubber 20 in which the organic solvent is dissolved is appropriately sent to the distillation column 16 when the solvent concentration reaches a predetermined amount or higher, and the organic solvent is recovered there. The water in the water scrubber 20 is not limited to the one that is circulated as in the illustrated example, and may be configured to pass through the water scrubber 20 once to several times and then be sequentially sent to the distillation column 16.

The distillation column 16 has a packed column 26, a condenser 28 provided above the packed column 26, and a reboiler 30 provided below the packed column 26. The packed tower 26 is
The filling material is filled in the flow path in the vertical direction, and the water of the water scrubber 20 flows in the middle of this flow path. When the water flowing into the packed tower 26 flows downward through the packing and the tower wall,
The low boiling point organic solvent evaporates to become an organic solvent vapor, which rises in the flow path and reaches the condenser 28. On the other hand, water descends as it is and flows into the reboiler 30.

The condenser 28 is a heat exchanger connected to a cooling device (not shown) and cools and condenses the rising organic solvent vapor. Here, the condenser 28 communicates with the solvent recovery tank 18, a part of the condensed organic solvent is refluxed to the packed tower 26, and the remaining liquid is the solvent recovery tank 18.
Will be collected. The reboiler 30 has a storage section that stores water and the like that hangs down from the packed tower 26 and a heater 30a that heats the water and the like in the storage section, and the drain pipe 32 is connected to the storage section. The reboiler 30 heats the water and the like in the storage portion by the heater 30a and evaporates a part thereof. In addition,
It goes without saying that the reboiler 30 has a temperature sensor, a temperature controller, a liquid amount sensor, etc., if necessary.

The distillation apparatus used in the solvent recovery spray dryer of the present invention is not limited to the one having the above-mentioned construction in which water is made to flow down in the packed column to separate the organic solvent. Gas-liquid contact means can also be used. The distillation column 16 using a packed column is particularly preferably used in terms of separation ability of organic solvent and downsizing of the apparatus.

Although the solvent recovery spray dryer of the present invention has been described above in detail, the present invention is not limited to the above-mentioned embodiments, and within the scope not departing from the gist of the present invention.
Of course, various improvements and changes may be made.

[0035]

As described above in detail, the solvent recovery spray dryer according to the present invention spray-drys a slurry containing a water-soluble organic solvent as a dispersion medium with a circulating gas, and then uses the circulating gas after spray-drying to produce an organic solvent. When collecting the solvent, it is not necessary to cool the refrigerant (or the organic solvent) to a low temperature as in the conventional device, and therefore the energy for that purpose can be greatly reduced. Further, a chilled water machine using atmospheric ventilation is sufficient for this cooling, and a large-sized and high-performance cooling device such as a refrigerator is not necessary, so that inexpensive mechanical equipment can be used. Moreover, since the temperature of the circulating gas after the recovery of the organic solvent is about 20 to 40 ° C., the thermal energy for reheating the circulating gas for performing the spray drying is significantly reduced as compared with the conventional device. be able to. Therefore, according to the solvent recovery spray dryer of the present invention, it is possible to carry out dry granulation by spray drying at low running cost with inexpensive mechanical equipment, which is extremely advantageous economically.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an example of a solvent recovery spray dryer of the present invention.

FIG. 2 is a schematic configuration diagram showing an example of a conventional solvent recovery spray dryer.

FIG. 3 is a schematic configuration diagram showing another example of a solvent recovery device in a conventional solvent recovery spray dryer.

[Explanation of symbols]

 10 1st collection | recovery apparatus 12 2nd collection | recovery apparatus 14,118,130 Cooling apparatus 16 Distillation tower 18,124 Solvent collection tank 20 Water scrubber 22,132 Pump 24,126 Heat exchanger 26 Packing tower 28 Condenser 30 Reboiler 102 Slurry pump 104 Atomizer 106 Heating device 108 Drying room 110 Cyclone 112 Bag filter 114,128 Solvent recovery device 116 Circulating gas blower

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location F26B 21/14 9140-3L

Claims (2)

[Claims] 1. A spray dryer for spray-drying a slurry containing a water-soluble organic solvent as a dispersion medium with a circulating gas to obtain a dry powder, wherein the circulating gas after spray drying is cooled to 10 to 50 ° C. A first recovery device for condensing and recovering the water-soluble organic solvent contained in the circulating gas is brought into contact with the circulating gas that has passed through the first recovering device by a water scrubber, so that the water-soluble organic substance contained in the circulating gas. A solvent recovery spray dryer, comprising: a second recovery device that absorbs and recovers a solvent in water. 2. The solvent recovery spray dryer according to claim 1, further comprising a distillation device for recovering the water-soluble organic solvent by distilling water having absorbed the water-soluble organic solvent in the second recovery device. Solvent recovery spray dryer.