JPS62221418A - Method and apparatus for regenerating solvent adsorbed activated carbon - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for regenerating activated carbon, particularly a method for regenerating activated carbon that has adsorbed a volatile solvent, and an apparatus for carrying out the method. Here, the term "volatile" solvent refers to a substance that is highly volatile compared to water, such as toluene, gasoline, alcohol, and the like.

[Conventional technology]

Steam has conventionally been generally used to recover the solvent adsorbed on activated carbon. The required amount of water vapor per 1 kg of recovered solvent is 3 to 8 kg.

The water vapor that comes out of the device after desorbing the solvent from the activated carbon is condensed without recovering the heat of condensation and then led to a decanter, where the water and solvent are separated. If they are not soluble, they will separate from each other. However, condensation heat loss is a problem. On the other hand, when the solvent to be recovered is dissolved in water, an appropriate separation device such as a distiller or a liquid-liquid extractor is used in place of the decanter. The solvent thus separated is recovered and the water optionally recycled, i.e.
It is returned to the boiler and reused to generate the steam for desorption.

During the recycling, the water, which still contains small amounts of solvent, must be purified.

For this reason, conventional activated carbon steam regeneration equipment generally includes a device for treating the water after decantation, in which residual solvent or solvent decomposition substances in the water are removed.

Therefore, for example, according to US Pat. No. 4,289,505, a complex system is proposed in which the aqueous phase leaving the decanter is itself treated with a bed of activated carbon.

If impure water is recycled directly, it will eventually lead to boiler blockages.

Processes in which water is recycled without purification, such as the process according to German Patent No. 1.202.764, are therefore of limited use and can only be used, for example, in the case of solvents with low solubility in water.

[Problem that the invention seeks to solve]

Therefore, it is an object of the present invention to provide an activated carbon regeneration method and device that does not involve the complexity of using activated carbon for regenerating activated carbon, and that is easy to operate and control and can suppress the loss of condensation heat as much as possible. It is something to do.

[Means for solving problems]

Therefore, according to the present invention, activated carbon adsorbing a volatile solvent is desorbed in an adsorption tower using steam from a boiler, the vapor coming out of the adsorption tower is condensed, and the condensed liquid is decanted. In a method for regenerating a solvent-adsorbing activated carbon, which includes various operations of carrying out the above-mentioned adsorption tower and recirculating the water obtained by this treatment, a first ejector interposed between the above-mentioned adsorption tower and the above-mentioned condensation condenser is used. In the first indirect heat exchanger placed under reduced pressure, the following two operations are carried out: This is an operation in which heat exchange is performed with impure water to generate steam from this impure water, and the steam is taken by the ejector into the high-pressure steam heading from the boiler to the adsorption tower. (bl) The impure water from the decanter is purified by steam distillation, and a small portion of the resulting purified water can be directly supplied to the boiler without the need for additional purification treatment. There is provided an activated carbon regeneration method characterized by simultaneously performing the following operations.

Furthermore, as equipment for carrying out this method, in addition to a boiler, an adsorption tower, a condenser, a decanter, and other separation means selected from among suitable separation means, the following means are further included: (a) an indirect heat exchanger,
The steam from the adsorption tower gives its heat to the impure water from the separation means, and the resulting impure vapor containing solvent vapor is sucked in by the ejector. a heat exchanger configured to directly reflux at least a portion of the water to be purified to the boiler;
and (b) means for sending impure water from the separation means to the heat exchanger and sending the purified water to the boiler. provided.

(Function) It is well known that a heat exchanger is used for heat recovery in the above-mentioned process. However, the indirect heat exchanger (hereinafter simply referred to as a heat exchanger) in this invention
The feature of the action is that the following two phenomena occur simultaneously.

That is, the first phenomenon is that heat exchange occurs between the solvent-containing vapor from the adsorption tower and the impure water from the decanter.
This impure water generates low-pressure steam, which is drawn into the high-pressure steam stream from the boiler to the adsorption tower by the ejector.

The second phenomenon is that a steam distillation operation is performed on the impure water from the decanter to produce pure water, which is so pure that it can be sent to the boiler without further treatment. This is a phenomenon in which the

〔Effect of the invention〕

In this way, most of the heat of the solvent-containing vapor from the adsorption column is recovered in the heat exchanger interposed between the adsorption column and the condenser, which provides a Low-pressure steam from the boiler is combined with high-pressure steam headed for the adsorption tower by the ejector, which improves the thermal efficiency of this system, and at the same time allows impure water from the decanter to be purified by distillation and sent directly to the boiler. Therefore, the cost for producing refined ice can be significantly reduced.

As described above, the method of the present invention is excellent from the viewpoint of energy saving.

And since the above heat exchange also acts as a wood refining device,
No separate refining equipment is required, and equipment costs are reduced accordingly.

Furthermore, in terms of the boiler, it is only necessary to generate high-pressure steam out of all the steam supplied to the adsorption tower, excluding the low-pressure steam sucked in by the ejector, so its operating cost is reduced.

Finally, unlike conventional methods in which a considerable amount of solvent mixed in condensed water was lost, in the method of the present invention, impure (solvent-containing) water is transferred from the decanter to a heat exchanger so that there is no loss of solvent. The solvent will not escape from the system during reflux.

Taking all of the above into consideration, when comparing the conventional technology and the method and apparatus of the present invention in terms of water vapor consumption required for 1 kg of solvent to be adsorbed onto activated carbon, the conventional method from a few years ago consumes approximately 3 to 4 kg in the best case. , whereas in the present invention, when using the second ejector described later, it is approximately 1.5 to 2.5 k
g.

In addition, when using a heat exchange accumulator described later, approximately 0
．． 5-1.5kg.

It has been proven that it makes a clear difference.

〔Example〕

Hereinafter, embodiments of the present invention will be described in conjunction with methods and apparatus thereof.

Figure 1 schematically illustrates the apparatus, in which the number (1) is a boiler for steam generation, this conventional boiler generates steam at a pressure of 8 to 16 bar; ) is an ejector (or thermal compressor) in which high-pressure steam from the boiler (1) expands to draw in low-pressure steam coming from the indirect heat exchanger (described later) through the duct (3). The number (4) indicates an adsorption tower.

In this adsorption tower, the solvent adsorbed on the activated carbon is absorbed by water vapor from the ejector (2). The mixed vapor (i.e. the mixture of water vapor and solvent vapor) is transferred to an adsorption column (
4) and flows into the pipe (5). This mixed vapor is led to an indirect heat exchanger (6), which is advantageously of the liquid film type with good heat exchange efficiency. Water containing impurities is also introduced into the heat exchanger (6) from the decanter (8), and mixed steam from the pipe (5) is used to evaporate this impure water.

This evaporation is carried out between 0.1 and 1 bar, preferably between 0.5 and 0.0 bar.
This is carried out under a vacuum of 8 bar, which vacuum itself is obtained in the ejector (2).

The pipe (5) enters the heat exchanger (6), where the unused portion (i.e. not taken off by the ejector) of the vapor mixture is finally condensed in a condenser (7) with indirect cooling. The cooling tower (7') supplies refrigerant to the condenser. The cold condensate produced by this condensation is transferred to a decanter (8).
The water and solvent are then separated by simple decantation, or by other suitable methods if the water and solvent are compatible. The solvent thus obtained is recovered, but the aqueous phase still contains some solvent and is therefore unsuitable for use in the boiler (1), so it is treated as follows.

That is, the above impure water is stored in the storage tank (9). Storage is also desirable since the system does not operate continuously.

The impure water coming out of the storage tank (9) passes through the pipe (14) to an indirect heat exchanger (hereinafter simply referred to as a heat exchanger) (
6) where it undergoes distillation. The resulting pure water flows down towards the bottom of the heat exchanger. Preferably, this is passed through a pipe (15) to a storage tank (
9), but the structure of this tank is such that a portion of the above pure water is mixed with impure water from the decanter (8), and the remainder is passed through a pipe (16) directly to the steam generating boiler (1). It is meant to be recycled.

However, for those skilled in the art, instead of a single tank (9) two
It will be clear that two tanks may be provided, one containing impure water from the decanter and the other containing pure water from the heat exchanger (6).

For example, if water containing 500 ppm of impurities is discharged from the decanter (8), if this is reduced to 50 ppm or less, it can be recycled to the boiler.

As mentioned above, the essence of the method of the present invention is that the mixed vapor (mentioned above) from the adsorption tower (4) is sent to the heat exchanger (6) which is depressurized by the ejector (2). Decanter
Thermal energy to heat the impure water supplied from (8) and stored in tank (9) is given from the mixed steam, and the heat exchange under low pressure that takes place here is on the one hand 0.1 to 1 This steam is drawn by the ejector (2) and is incorporated into the high-pressure steam flowing from the boiler (1) to the adsorption tower (4). Since this occurs (i.e., the mixed solvents in the water from the decanter mostly migrate into the steam drawn by the ejector), pure water is produced here, a portion of which is sent directly to the boiler. The remainder is mixed with impure water from the decanter (8) and then returned to the heat exchanger (6), and is not used in the heat exchanger (i.e., is not used in the ejector during steam distillation). The portion (not subtracted) is finally condensed in the condenser (7).

On the other hand, it will also be clear from the foregoing that the equipment used to carry out the method of the invention for activated carbon regeneration comprises a boiler, an adsorption column, a condenser, and a decanter or other suitable separator. . However, the main feature of the device is that it includes a heat exchanger (6) constructed and arranged so that the mixed vapor from the adsorption column (4) imparts a portion of its heat to the impure water from the decanter (8). This is because we are equipped with
This heat exchanger generates impure steam (i.e. water vapor mixed with solvent vapor) at a pressure of 0.1 to 1 bar on the one hand and takes it to the ejector (2), and on the other hand Therefore, the apparatus according to the invention described above has as an additional requirement a means for supplying the impure water from the decanter to the heat exchanger, and a means for supplying the obtained pure water. means for supplying the boiler with
It is equipped with the following.

[Another example]

Another embodiment will be described below, but before a specific description with reference to the drawings, the following three points (al, tb) and (C) will be explained in principle.

at First of all, the following facts must be considered.

(i) The process of the invention (which involves heating and evaporating impure water introduced into a heat exchanger) operates efficiently because:
This is the case when the activated carbon in the adsorption tower is already heated sufficiently that the steam leaving the adsorption tower can donate most of its heat to the impure water. At the beginning of the desorption process, water vapor that reaches the relatively low temperature activated carbon condenses on its surface. The condensed water remains between the granular activated carbon particles, adheres to the inner wall surface of the adsorption tower, or simply flows toward the bottom.

In other words, no steam is discharged from the adsorption tower during this period, and the energy recovery system of the present invention does not operate.

(iii) (When there is only one adsorption tower), the process according to the present invention is discontinuous, and the activated carbon that has adsorbed the solvent is transferred from the original adsorption tower to the desorption tower rather than the adsorption tower in the present invention. The method is to sequentially carry out various steps such as a step of transferring the activated carbon to a column (to be called a column), a step of heating this activated carbon with steam, a step of substantial desorption, and then a step of cooling the activated carbon after desorption.

In view of this, it is desirable to configure a system for the method of the present invention in which the original adsorption tower is combined with another adsorption tower to recover the thermal energy of the steam emitted from these adsorption towers. Regarding the operation of the entire system, it is desirable that the heat exchanger is operated continuously.In other words, while one adsorption tower is connected to the system and is in the thermal desorption process, the other adsorption tower is connected to the system and is in the thermal desorption process. It is convenient if the adsorption tower is in the original adsorption process.

That is, in another embodiment of the present invention, the heat exchanger is connected to two adsorption towers, and although these adsorption towers are arranged in parallel, they are operated in a staggered cycle.

(bl) The second thing to consider is that, as is clear when considering the activated carbon desorption process using steam, and as mentioned above, during the initial stage, steam is consumed to raise the temperature of the activated carbon, and the steam is removed from the adsorption tower. The above-mentioned mixed vapor is not discharged at all.Next, a mixed vapor containing a high concentration of the adsorbed solvent comes out of the adsorption tower (sometimes called a desorption tower), but its condensation temperature is extremely high. There is a middle period when the steam pressure is low enough to be drawn by the ejector.Finally, there is a late period when the water vapor content in the mixed vapor coming out of the adsorption tower increases until the temperature reaches a sufficiently high temperature. As a result, the steam pressure generated in the heat exchanger becomes high enough to activate the ejector that sucks it.

Therefore, in the middle period (that is, the second desorption period), a second ejector different from the ejector (first ejector) is arranged to start the first ejector, and a pressure of 8 to 16 bar from the boiler is applied. High-pressure steam may be supplied to the second ejector, and the steam emitted from the second ejector may be guided to the suction side of the first ejector. The second ejector can also be short-circuited and left unused during the intermediate period.

The suction side of the second ejector is preferably connected to a second heat exchanger arranged in series with the (ie first) heat exchanger. This is advantageous because the heat exchange efficiency is improved.

The vapor enriched with solvent in the first heat exchanger condenses in the second heat exchanger, which is operated at a lower temperature than the first heat exchanger.

(C) Finally, in the third period, that is, the latter half, as mentioned above, the water vapor content in the mixed vapor coming out of the adsorption tower gradually increases, so that it condenses at a sufficiently high temperature.

Therefore, a water-rich vapor mixture that condenses at still higher temperatures (approximately 80-95° C.) is collected at the outlet of the heat exchanger. To optimize energy efficiency or conditions, the above (first)
The steam coming out of the heat exchanger is transferred to the heat exchange accumulator (second
It is advantageous if the vapor heats a suitable liquid heating medium by indirect heat exchange. The heat thus stored in the heating medium is utilized at the beginning of the desorption step in the form of vapor of another liquid heated by the heating medium.

In this way, the heating of the heat medium by the steam from the (first) heat exchanger is carried out not only during the latter period of the desorption process, but also during a part of the middle period (second period). It will be destroyed.

The heat exchanger or the second heat exchanger may be short-circuited or bypassed during all or part of the initial and middle stages of the desorption process, and may be left unused. The heating medium is a compound or a mixture thereof that changes state or undergoes some reversible change, in particular from solid to liquid or vice versa during the operating cycle, i.e. liquefies at the end of the desorption process. It is sufficient if it solidifies at the beginning of the next cycle.

Steam generation using this heating medium is performed by a method of spraying water in the form of a mist toward the surface of a container containing the heating medium.

The other embodiments outlined above will be described in detail below with reference to FIGS. 2 to 4.

Figure 2 shows boiler (1), ejector (2), adsorption tower (4)
, shows only the main parts of the entire device when a second ejector (11) is provided in addition to the heat exchanger (6), and this second ejector (11) is shown.
1), water vapor from the boiler (1) passes through the valve (24).
The steam from the heat exchanger (6) is thus drawn in by the second ejector (11) through the valve (25). Second ejector (11) via pipe (27)
is connected to the suction side of the first ejector (2). Second
While the ejector is in operation, the (first) ejector (11)
The steam supply to is shut off by valves (23) and (26).

Another alternative embodiment is shown in FIG. Here, the second ejector (
The suction side of 18) is connected to the second heat exchanger (17). Steam passing through the first heat exchanger (6) from the adsorption tower (4) enters the second heat exchanger (17), and the second ejector (18) passes through the valve (19) to the boiler (1). )
The outlet is the first ejector (2).
is connected to the suction side of the valve (20) via a valve (20).

In FIG. 4 showing a further different embodiment, the number (
1) is the boiler, (2) is the first ejector that receives the steam from the boiler (1), and sucks the steam from the first heat exchanger (6) through the duct (3), and number (4) is the adsorption tower. , (5) is a pipe that sends vapor from the adsorption tower to the heat exchanger, (7) is a condenser that receives refrigerant from the cooling tower (7°),
(8) is a decanter, which is a piece of equipment in a system that recycles impure water from a distance of 4 km to a tank (9) via a pipe (10).

Number (12) indicates a heat exchange accumulator as a second heat exchanger, and in this example, tubes (43) arranged in parallel in the vertical direction are installed inside. These tubes are filled with a heat medium, such as a salt compound that melts at about 80 to 90°C. The accumulator (12) is also equipped with a group of nozzles (44), and the liquid supplied thereto is either pure or generally pure water (that is, water containing almost no solvent) or a pipe (41). ) is the impure water extracted from the water. The above accumulator (12
) is supplied with steam from the heat exchanger (6) through a pipe (45) equipped with a valve. This steam leaves the accumulator into another pipe (46) with a valve. The above-mentioned valves provided in the pipes (45) and (46) are used to isolate the agie emulator (12) from other parts of the system, and at this time it is in a bypassed state by the pipe (47). The liquid condensed in the accumulator (12) is taken out from the pipe (48) and guided to the tank (9), while the steam generated in the accumulator is sucked into the ejector (2) through the pipe (49). .

[Brief explanation of drawings]

Figures 1 to 4 are flow sheets showing an embodiment of the apparatus for the method of the present invention.

Claims (1)

[Scope of Claims] [1] Activated carbon adsorbing a volatile solvent is desorbed in an adsorption tower using steam from a boiler, the vapor coming out of the adsorption tower is condensed, and the condensed liquid is treated with decane. In a method for regenerating solvent-adsorbing activated carbon, which includes various operations of carrying out a cation treatment and recirculating the water obtained from this treatment, a first In the first indirect heat exchanger, which is placed under reduced pressure by the ejector, the following two operations are carried out: This is an operation for generating steam from the impure water by exchanging heat with the impure water, and the steam is taken by the ejector into the high-pressure steam flowing from the boiler to the adsorption tower. and (b) purifying the impure water from the decanter by steam distillation so that at least a portion of the resulting purified water can be directly supplied to the boiler without the need for additional purification treatment. An activated carbon regeneration method characterized by simultaneously carrying out the following operations. [2] The impure water discharged from the decanter and stored in the storage tank is subjected to heat exchange under reduced pressure in the heat exchanger under reduced pressure by the ejector, and the impure water is transferred to the solvent-containing water from the adsorption tower. 0.1 to 1 by using the heat of steam
The ejector generates low-pressure steam of a bar and introduces it into the high-pressure steam stream from the boiler to the adsorption tower, and at least a portion of the purified water produced by the steam distillation action from the low-pressure steam generation is transferred to the ejector. While refluxing to the boiler, the remainder of this purified water is mixed with the impure water from the decanter and recycled to the heat exchanger, and the vapor from the adsorption column that has not condensed in the heat exchanger is further recycled. The activated carbon regeneration method according to claim (1), wherein the activated carbon is condensed by a condenser disposed between the heat exchanger and the decanter. [3] The activated carbon regeneration method according to claim (1), wherein the heat exchanger is connected to two adsorption towers, and these two adsorption towers are operated in a staggered cycle. [4] For a period of time within the period of the desorption process, the first
In order to start the ejector with another second ejector connected to the heat exchanger, steam is supplied from the boiler to the second ejector, and the second ejector connected to the suction side of the first ejector is started. The activated carbon regeneration method according to claim 1, wherein the ejector can be selectively short-circuited and rendered inoperative at other times within the above period. [5] The second ejector places the inside of the second heat exchanger arranged in series with the first heat exchanger under reduced pressure, and the discharge side of the second ejector is connected to the first heat exchanger. The activated carbon regeneration method according to claim (4), which communicates with the suction side of the ejector. [6] During a period of time during the desorption process, the first heat exchange accumulator as the second heat exchanger is
The liquid from the heat exchanger is sent to perform indirect heat exchange with the heat medium in the accumulator to store heat in the heat medium, and in the subsequent cycle in which the activated carbon is heated and desorbed. The activated carbon regeneration method according to claim (1), wherein water is heated by a heating medium to generate steam, which is sent to an adsorption tower. [7] Boiler (1), adsorption tower (4), and condenser (
7) and suitable separation means selected from decanters (8) and other separation means, in addition to the following means: (a) an indirect heat exchanger (6); The above adsorption tower (4
) imparts its heat to the impure water from the separating means (8) and the impure vapor containing solvent vapor thereby generated is sucked in the ejector (2), while the impure vapor is (b) a heat exchanger having a structure suitable for directly refluxing at least a portion of the water purified as it is generated to the boiler (1); 6) and means for sending the purified water to the boiler (1).