JP2009154115A - Solvent-containing gas treatment apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solvent-containing gas treatment apparatus keeping the oxygen gas concentration in a regeneration gas zone sufficiently lower than a limit oxygen concentration, and greatly reducing consumption of nitrogen to efficiently perform the adsorption/desorption treatment. <P>SOLUTION: In the solvent-containing gas treatment apparatus composed of a zone including a raw gas adsorbing zone 11, an additional adsorbing zone 14, a first regeneration zone 13, a second regeneration zone 12, and a cooling zone 20, formed by dividing an adsorption boy 1 consisting of an adsorption element containing an adsorption material, the adsorption element is composed of a sheet having a gas permeability of 5.0 L/m<SP>2</SP>/sec or less at an inlet pressure of 50 mmH<SB>2</SB>O. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  In the present invention, the solvent-containing gas is sequentially moved to the adsorption zone, the regeneration zone, and the cooling zone in which the adsorbents composed of the adsorbing elements are separated, and the adsorption and desorption of the solvent of the predetermined component can be performed efficiently and safely. The present invention relates to a solvent-containing gas processing apparatus that can be used.

  Conventionally, as a method of treating organic solvent gas generated from various factories, this organic solvent gas is adsorbed with an adsorbent such as activated carbon, then steam is blown into the adsorbent, and the adsorbed components are desorbed and recovered and regenerated by desorption. In general, the organic solvent gas is again passed through the adsorbent thus adsorbed, and the organic solvent is continuously adsorbed and desorbed.

  However, the method of directly blowing water vapor into the desorption has problems such as the generation of waste water of condensed water due to a large amount of water vapor at the time of desorption, and the decomposition of the recovered solvent component by promoting contact with the water vapor. A desorption method other than the simple method has been desired.

  As a method of recovering the organic solvent without directly blowing water vapor at the time of desorption, the adsorbent is circulated between the adsorbing part and the desorbing part, and the adsorbent and the desorption are continuously performed. There is a continuous method in which an organic solvent is concentrated and recovered by performing adsorption and desorption in multiple stages.

  As a fluidized method, for example, Patent Document 1 discloses a multistage fluidized bed adsorption / desorption method and apparatus using granular activated carbon. However, since this method adsorbs granular activated carbon while flowing, the exhaust concentration cannot be kept low. In addition, there is a problem that the granular activated carbon is worn by the flow and crushed activated carbon waste is scattered.

  As a continuous method, for example, Patent Document 2 and Patent Document 3 disclose an adsorption / desorption method and apparatus using a rotating adsorbent. A continuous method using this rotary adsorber will be described below with reference to FIG.

  FIG. 1 shows a solvent-containing gas processing apparatus using a cylindrical rotary adsorber. The cylindrical rotary adsorber 1 is provided with a raw gas adsorption zone 11, a supplementary adsorption zone 14, a first regeneration zone 13, and a second regeneration zone 12 in order clockwise from FIG. A cooling zone 20 is provided at a position during the transition to the raw gas adsorption zone 11.

  Here, the rotary adsorbent conventionally used is formed by step-processing a sheet-like adsorbent paper obtained by paper making an adsorbent and a fibrillated synthetic pulp having flame resistance and heat resistance. This is a disc honeycomb type honey rotor formed into a cylindrical honeycomb shape.

  The raw gas containing the organic solvent is supplied to the raw gas adsorption zone 11 by the supply fan 5a. The organic solvent in the raw gas is adsorbed by the adsorbent while passing through the raw gas adsorption zone 11 in the direction of the arrow A1, and is discharged as clean air from the exhaust duct 11a.

  Gas that has passed through the additional adsorption zone 14 in the direction of arrow A2 is introduced to the inlet side of the cooling zone 20 before the adsorbent moves to the raw gas adsorption zone 11, and the introduced gas is cooled along the direction of arrow C. The adsorbent is cooled by passing through the 20 adsorbents so that the solvent is easily adsorbed in the raw gas adsorption zone 11. On the other hand, the gas whose temperature has been increased by heat exchange with the adsorbent is introduced to the inlet side of the heater 6a and used as a desorption gas in the second regeneration zone 12. Next, the gas that has passed through the second regeneration zone 12 in the direction of the arrow E1 and desorbed the organic solvent from the adsorbent in the second regeneration zone 12 is supplied to the cooler 9 via the fan 5b, and after cooling, the additional adsorption zone 14, the organic solvent desorbed in the second regeneration zone 12 is adsorbed, and the outlet gas of the additional adsorption zone 14 is further circulated to the inlet side of the cooling zone 20. In the additional adsorption zone 14, since the solvent desorbed in the second regeneration zone 12 after the raw gas adsorption zone 11 is further adsorbed, the amount of adsorbent adsorbed in the additional adsorption zone 14 can be increased. As a result, the desorption gas in the first regeneration zone 13 described below is in a state containing an organic solvent at a high concentration.

  By the way, in many common organic solvents, the vapor is flammable, and in the presence of solvent vapor (gas) and air (oxygen), there is a certain explosion limit concentration (upper limit, lower limit) for each solvent. If there is an ignition source, the solvent gas with a concentration in that range will cause explosion combustion. Although the range of the explosion limit concentration differs somewhat depending on the solvent type, the range of 1 to 3% of the concentration in the air for most solvents is the lower limit of explosion.

  On the other hand, when an inert gas (nitrogen or the like) is added to lower the oxygen concentration in the gas, the explosion limit concentration range becomes narrower, and below a certain oxygen concentration, any solvent gas composition enters the incombustible region. The oxygen concentration (limit oxygen concentration) where the solvent gas enters the non-flammable region varies depending on the solvent type as well as the range of the explosion limit concentration, but in most solvents, the limit oxygen concentration is 10% or more (translated by High Pressure Gas Safety Association; Flammability) Characteristics of Combustible Gases and Vapors, 1971).

  In the continuous adsorption / desorption apparatus using the rotary adsorber, the gas desorbed in the first regeneration zone 13 contains a solvent at a high concentration, and its concentration is about 30 to 40 times the concentration of the raw gas. Become. Therefore, even when the raw gas has a relatively low concentration of about 1000 ppm, the desorption gas concentration is 30000 ppm (3%) or more, which exceeds the lower explosion limit concentration. Therefore, as a safety measure against the explosive combustion of the desorption gas in the first regeneration zone 13, it is necessary to make the oxygen concentration of the desorption gas below the critical oxygen concentration. Normally, it is desirable to manage the oxygen concentration in the solvent gas within the explosion limit concentration range from 1/3 to 1/4 of the limit oxygen concentration (oxygen concentration 3% or less) for safety reasons. A method of replacing oxygen with an inert gas is common.

  Therefore, in the first regeneration zone 13, the nitrogen gas heated by the heater 6b is passed through the first regeneration zone 13 in the direction of arrow E2, and the oxygen concentration is adjusted to be 1/3 to 1/4 or less of the limit oxygen concentration. While performing, the organic solvent is desorbed from the adsorbent in the first regeneration zone 13. The desorbed organic solvent gas is introduced into the condenser 8, and the organic solvent is condensed and recovered. In order to obtain a high concentration before introduction into the condenser 8, a bypass path 10 and a fan 5c are provided to form a path for circulating the exhaust gas on the outlet side of the condenser 8 to the inlet side of the first regeneration zone 13. Yes.

  In this way, the continuous method using a rotating adsorbent allows the adsorbent to be heated quickly and uniformly by using heated air for desorption, and also uses the above-mentioned circulation path for safe and efficient adsorption. There is an advantage that the desorption process can be stably increased.

  However, in the case of such an adsorption / desorption processing apparatus in which such a rotary adsorber passes through a plurality of zones, each zone is divided by an independent partition (header) at both end faces of the adsorbent, but the adsorbent rotates. Therefore, a certain gas leak occurs in adjacent zones. There are also gases that are taken out into adjacent zones by the rotation of the adsorbent, or are brought back in. Furthermore, since the adsorbent itself also has gas permeation, the circulating gas in the first regeneration zone 13 leaks into the adjacent zone, and the amount of nitrogen used for adjusting the oxygen concentration increases.

In order to reduce the gas (nitrogen) leaking from the first regeneration zone 13, conventionally, the static pressure of each zone is adjusted by a fan or the like in FIG. 1 to reduce the leakage of the gas from the first regeneration zone 13 to the adjacent zone. However, there is a problem that gas leaks from the sheet to the adjacent zone due to a slight breakdown of the static pressure balance.
JP 52-14580 A JP 63-236514 A JP 2005-238046 A

  The present invention has been made in view of the problems of the prior art, and in a continuous adsorptive desorption apparatus using a rotating adsorber, the problem is solved by reducing the gas permeability, and the regenerated gas. An object of the present invention is to provide a solvent-containing gas treatment device that can maintain an oxygen gas concentration in a zone sufficiently lower than a critical oxygen concentration and that can perform an efficient adsorption / desorption treatment by greatly reducing the amount of nitrogen used. Is.

That is, in the present invention, an adsorbent composed of an adsorbing element containing an adsorbent is divided into a solvent containing a zone including a raw gas adsorption zone, a supplemental adsorption zone, a first regeneration zone, a second regeneration zone, and a cooling zone. In the gas processing apparatus, the adsorption element is composed of a sheet having a gas permeability of 5.0 L / m ² / sec or less at an inlet pressure of 50 mmH ₂ O.

  In a preferred embodiment of the solvent-containing gas processing apparatus of the present invention, the solvent-containing gas passes continuously or intermittently in the order of the raw gas adsorption zone, the additional adsorption zone, the first regeneration zone, the second regeneration zone, and the cooling zone. The gas discharged from the additional adsorption zone is connected to the cooling zone, the gas discharged from the cooling zone is connected to the second regeneration zone, and the gas discharged from the second regeneration zone is connected to the additional adsorption zone The circulation path is formed, nitrogen is introduced into the desorption gas line of the first regeneration zone, and all or part of the desorption gas desorbed from the first regeneration zone is recovered by a condenser, and the adsorption element is cylindrical. Or it is cylindrical, the structure of the adsorption element is a honeycomb, and the adsorbent is zeolite.

  The solvent-containing gas treatment apparatus of the present invention has an extremely small gas permeability of the adsorbent itself using an adsorption element composed of a sheet with extremely low gas permeability, so there is little gas leakage between zones, Even if the amount of nitrogen used is reduced, the oxygen concentration can be kept sufficiently low, and the solvent-containing gas can be processed efficiently and safely at low cost.

  The solvent-containing gas processing apparatus of the present invention basically has the configuration of the solvent-containing gas processing apparatus shown in FIG. 1 used in the description of the prior art, and the detailed configuration is as described above. Since it is known to those skilled in the art, it will not be described in further detail.

The greatest feature of the solvent-containing gas processing apparatus of the present invention is that the adsorption element is composed of a sheet having extremely low gas permeability. Specifically, the adsorption element used in the present invention is 5.0 L / m ² / sec or less, preferably 1.0 L / m ² / sec or less, more preferably 0.5 L / m at an inlet pressure of 50 mmH ₂ O. ^{It is} composed of a gas permeable sheet of ² / sec or less. The gas permeability of the sheet is performed as follows. A sheet to be measured is cut to a size of about 50 mm, and the cut sheet is mounted on a measuring device and installed so that gas is blown perpendicular to the sheet. Supply N ₂ gas to the measuring equipment and wait until the inlet pressure is constant. After confirming that the inlet pressure is constant, measure the gas permeation per unit time and unit area on the outlet side of the measurement equipment. The inlet pressure 10mmH _{2 O,} 25mmH _{2 O,} and four 50 mm H ₂ O and 100 mm H ₂ O, for 3 times by one measured for each pressure, ensure that the pressure and the gas permeation amount proportional to create a chart The average of the measured values at an inlet pressure of 50 mmH ₂ O is defined as the gas permeability of the sheet.

  As a sheet | seat used for an adsorption | suction element, what carried the adsorption material on the inorganic fiber sheet is preferable. The reason for this is that the gas permeability is high in a sheet obtained by papermaking an adsorbent and fibrillated pulp by a wet papermaking method or the like as in the prior art. Further, even if an inorganic binder or the like is applied to a sheet prepared by a wet papermaking method or the like to reduce gas permeability, the effect up to the level of gas permeability of the sheet using the inorganic fiber sheet cannot be obtained. Further, in order to make the gas permeability comparable to that of the inorganic fiber sheet, when a large amount of inorganic binder is applied, the paper thickness becomes thick, and when processed into an adsorption element, the air pressure loss increases. Furthermore, since the adsorbent content ratio in the sheet is extremely lowered and the flexibility of the sheet is extremely deteriorated, the sheet cannot be processed into an adsorbing element in a subsequent process.

Examples of the adsorbent used in the adsorption element include zeolite, silica gel, activated alumina, and the like, with zeolite being preferred. Further, zeolite having a pore diameter of 7 mm or more is desirable, and X-type zeolite or Y-type zeolite is preferable. The specific surface area of the adsorbent is preferably in the range of 500 to 1500 m ² / g. If the pore diameter is smaller than 7 mm and the specific surface area is smaller than 500 m ² / g, the high concentration gas cannot be adsorbed in the additional adsorption zone, and the removal performance is reduced.

  In the present invention, the adsorption element is preferably columnar or cylindrical, and the structure is preferably honeycomb. The columnar shape refers to a shape in which a honeycomb is wound around a core material to form a rotor, and the cylindrical shape is formed by stacking a plurality of honeycombs so that gas can flow in parallel, and the processing gas is vented in the radial direction from the center. Thus, it refers to a shape in which honeycomb laminated bodies are arranged circumferentially. Thus, by providing the adsorption zone and the regeneration zone in a cylindrical shape or a columnar shape and rotating around the central axis, the adsorption and regeneration processes can be performed efficiently and continuously. Compared with the pressure loss, the pressure loss can be reduced.

Hereinafter, the excellent effect of the solvent-containing gas processing apparatus of the present invention will be described in detail based on Examples and Comparative Examples.
<Example>
An inorganic fiber sheet carrying zeolite was formed into a 900 mmφ cylindrical honeycomb shape to form a disk-type honeycomb rotor. The gas permeability of the sheet was 0.2 L / m ² / sec when the inlet pressure was 50 mmH ₂ O. The honeycomb rotor is divided into a raw gas adsorption zone 11, a supplemental adsorption zone 14, a first regeneration zone 13, a second regeneration zone 12, and a cooling zone 20 by partition walls that are divided in the circumferential direction. The angles were set to °, 85 °, 50 °, 45 ° and 30 °.

The circulating air volume in the additional adsorption zone 14, the first regeneration zone 13, and the cooling zone 20 is 2.1 Nm ³ / min, the circulating air volume in the first regeneration zone 13 is 2.3 Nm ³ / min, and the air volume introduced into the condenser 8 is It was set to 0.8 m ³ / min. Further, the oxygen concentration was measured by gradually reducing the nitrogen introduced into the circulating gas in the first regeneration zone 13 from 60 L / min. The inlet gas temperature of the first regeneration zone 13 and the second regeneration zone 12 is set to 130 ° C., the outlet gas temperature of the condenser 8 is set to 10 ° C., and the desorption gas of the first regeneration zone 13 is changed to isopropyl alcohol. (IPA) was condensed and recovered. The IPA concentration at the outlet of the first regeneration zone 13 was 40000 to 50000 ppm, which was within the explosion limit concentration range (in the case of IPA, the lower limit is 2.0 vol% and the upper limit is 7.9 vol%).

  As the amount of nitrogen introduced into the first regeneration zone 13 increases, the oxygen concentration of the desorption concentrated gas circulating in the first regeneration zone 13 decreases, but the nitrogen amount is 20 L / min (nitrogen / raw gas amount ratio = 1 / 300), the oxygen concentration in the first regeneration zone 13 is 2.8%, which is about 1/6 of the critical oxygen concentration (IPA's critical oxygen concentration is 17%), and the nitrogen amount is 40 L / min (nitrogen / raw material). When the gas amount ratio was increased to 1/150), the oxygen concentration in the first regeneration zone 13 was reduced to 0.9%, and a very low oxygen concentration was achieved. The IPA removal rate was stable at about 98.0%.

<Comparative example>
As a comparative example, a sheet-like activated carbon paper obtained by papermaking powdered activated carbon and fibrillated synthetic pulp having flame retardancy and heat resistance is stepped, and at an inlet pressure of 50 mmH ₂ O, 15 L / m ² / A sec-type sheet was formed into a cylindrical honeycomb shape, and a disk-type honeycomb rotor was produced in the same manner as in the example. And the to-be-processed gas (IPA) was cleaned and collect | recovered on the same conditions as the Example.

  In the comparative example, when the nitrogen amount is 20 L / min (nitrogen / raw gas amount ratio = 1/300), the oxygen concentration in the first regeneration zone 13 is 6.7%, and the nitrogen amount is 40 L / min (nitrogen / raw gas). In the case of the quantity ratio = 1/150), the oxygen concentration in the first regeneration zone 13 was 2.7%, and the oxygen concentration was about three times higher than in the example. The IPA removal rate was stable at about 97.5%. Furthermore, in the comparative example, the static pressure balance must be adjusted with a fan, a damper, or the like. When these balances are lost, the amount of nitrogen used is further increased to keep the oxygen concentration low.

  As described above, the apparatus of the example can make the oxygen concentration in the desorption concentrated gas of the first regeneration zone 13 sufficiently lower than the limit oxygen concentration with a smaller amount of nitrogen than the apparatus of the comparative example. It was. This is because, as described above, since the adsorption element having extremely low gas permeability is adopted as the adsorption element, there has been almost no gas leaked from the first regeneration zone to the adjacent zone. Further, by adopting an adsorption element with extremely low gas permeability, a circulation gas line (a supplementary adsorption zone 14 and a cooling zone 20) circulating in the additional adsorption zone adjacent to the first regeneration zone and the second regeneration zone. The circulation gas line circulating through the additional adsorption zone 14 through the second regeneration zone 12) also obtained a result of stable operation at an oxygen concentration of about 2%. Furthermore, the apparatus of the embodiment does not need to take into consideration the adjustment of the static pressure balance of each zone by a fan or the like that has been conventionally performed.

  According to the solvent-containing gas processing apparatus of the present invention, since the adsorption element having extremely low gas permeability is used, there is little gas leakage between zones, and the oxygen concentration can be kept sufficiently low even with a very small amount of nitrogen used. It is possible to remove and recover the solvent efficiently and safely at a low running cost.

An example of the solvent containing gas processing apparatus using a cylindrical rotation adsorption body is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Adsorbent body 5a Supply fan 5b, 5c Fan 6a, 6b Heater 8 Condenser 9 Cooler 10 Bypass path 11 Raw gas adsorption zone 11a Exhaust duct 12, 13 Regeneration zone 14 Additional adsorption zone 20 Cooling zone

Claims (6)

In a solvent-containing gas processing apparatus that divides an adsorbent composed of an adsorbing element containing an adsorbent and constitutes a zone including a raw gas adsorption zone, a supplementary adsorption zone, a first regeneration zone, a second regeneration zone, and a cooling zone, A solvent-containing gas processing apparatus, wherein the adsorption element is composed of a sheet having a gas permeability of 5.0 L / m ² / sec or less at an inlet pressure of 50 mmH ₂ O.   The solvent-containing gas is configured to pass continuously or intermittently in the order of the raw gas adsorption zone, the additional adsorption zone, the first regeneration zone, the second regeneration zone, and the cooling zone, and the gas discharged from the additional adsorption zone Connected to the cooling zone, the gas discharged from the cooling zone is connected to the second regeneration zone, and the gas discharged from the second regeneration zone forms a circulation path connected to the additional adsorption zone, and the first regeneration zone The solvent-containing gas processing apparatus according to claim 1, wherein nitrogen is introduced into the desorption gas line.   3. The solvent-containing gas processing apparatus according to claim 1, wherein all or part of the desorbed gas desorbed from the first regeneration zone is recovered by a condenser.   The solvent-containing gas processing apparatus according to claim 1, wherein the adsorption element is columnar or cylindrical.   The solvent-containing gas processing device according to any one of claims 1 to 4, wherein the adsorption element has a honeycomb structure.   The solvent-containing gas processing apparatus according to any one of claims 1 to 5, wherein the adsorbent is zeolite.