JP2006150207A - Washing solution for nitrogen oxide absorbent, and washing method and regeneration method of nitrogen oxide absorbent using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a washing solution for a nitrogen oxide absorbent greatly suppressing lowering of the intensity of the absorbent, a washing method and a regeneration method of the nitrogen oxide absorbent using it. <P>SOLUTION: The washing solution is for washing the nitrogen oxide absorbent which is formed by holding a nitrogen oxide absorbing component on a base material containing at least one material among hydroxide, sulfate and carbonate of at least one of Ca and Al. The solution consists of an aqueous solution containing at least one of hydroxide, sulfate and carbonate of at least one of Ca and Al. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a cleaning liquid for cleaning a used nitrogen oxide absorbent which is disposed in a tunnel or the like and absorbs and removes nitrogen oxide in exhaust gas from an automobile or the like, and cleaning of a nitrogen oxide absorbent using the same. The present invention relates to a method and a reproduction method.

Examples of the nitrogen oxide absorbent that is disposed in a tunnel or the like and absorbs and removes nitrogen oxide in exhaust gas from automobiles, for example, activated carbon, slaked lime (Ca (OH) ₂ ), gypsum (CaSO ₄ ), and the like. There is a mixed honeycomb type or pellet type base material in which an absorption component made of an alkali salt such as potassium hydroxide (KOH) is held.

Such a nitrogen oxide absorbent accumulates dust and dirt on the surface as it is used, and the ability to absorb nitrogen oxides by the absorbing component deteriorates. After being removed from water, dust, dust, and reactive organisms such as potassium nitrite (KNO ₂ ) and potassium nitrate (KNO ₃ ) are washed away and then immersed in an aqueous solution containing an absorbent component. Is re-supplied and re-installed in a tunnel or the like for reuse (see, for example, Patent Documents 1 and 2 below).

Japanese Patent Laid-Open No. 11-147038 JP 2000-167394 A

  However, if the cleaning of the nitrogen oxide absorbent as described above is repeated, the strength of the nitrogen oxide absorbent decreases, and the nitrogen oxide absorbent cannot be reused. There was a problem. Specifically, when the cleaning process is performed 5 times, the mechanical strength becomes about 80% compared to the initial level, and when the cleaning process is performed 10 times, the mechanical strength is about 70% compared with the initial level. It was about%.

  For this reason, the present invention provides a cleaning solution for a nitrogen oxide absorbent capable of greatly suppressing a decrease in the strength of the nitrogen oxide absorbent, and a cleaning method and a regeneration method for a nitrogen oxide absorbent using the same. The purpose is to provide.

  A cleaning solution for a nitrogen oxide absorbent according to the present invention for solving the above-mentioned problems is a base material containing at least one mold material of at least one of Ca, Al hydroxide, sulfate, and carbonate. And a cleaning liquid for cleaning a nitrogen oxide absorbent that retains a nitrogen oxide absorbing component that absorbs nitrogen oxide, wherein at least one of hydroxides, sulfates, and carbonates of Ca and Al. It consists of the aqueous solution containing one.

  In addition, the nitrogen oxide absorbent cleaning liquid according to the present invention is characterized in that, in the above-described nitrogen oxide absorbent cleaning liquid, the cleaning liquid is composed of an aqueous solution of the mold material contained in the substrate.

  In addition, the nitrogen oxide absorbent cleaning liquid according to the present invention is an aqueous solution containing up to a saturation state in the nitrogen oxide absorbent cleaning liquid described above.

  In addition, a method for cleaning a nitrogen oxide absorbent according to the present invention is characterized in that the nitrogen oxide absorbent is cleaned using the above-described nitrogen oxide absorbent cleaning solution.

  In addition, the method for regenerating a nitrogen oxide absorbent according to the present invention is a method of cleaning the nitrogen oxide absorbent using the nitrogen oxide absorbent cleaning liquid described above, and then performing the nitrogen oxidation on the nitrogen oxide absorbent. The substrate is replenished with the nitrogen oxide absorbing component by impregnating with an aqueous solution of the substance absorbing component.

  According to the nitrogen oxide absorbent cleaning liquid and the nitrogen oxide absorbent cleaning method and regeneration method using the same according to the present invention, the strength reduction of the nitrogen oxide absorbent can be greatly suppressed. The number of times it can be used can be greatly increased.

  Embodiments of a nitrogen oxide absorbent cleaning solution and a nitrogen oxide absorbent cleaning method and regeneration method using the same according to the present invention will be described below.

  The nitrogen oxide absorbent cleaning liquid according to the present embodiment absorbs nitrogen oxide in a base material containing at least one mold material of at least one of Ca, Al hydroxide, sulfate, and carbonate. A cleaning liquid for cleaning a nitrogen oxide absorbent that retains a nitrogen oxide absorbing component, and from an aqueous solution containing at least one of Ca, Al hydroxide, sulfate, and carbonate It will be.

  Here, the base material of the nitrogen oxide absorbent is composed of the mold material and activated carbon to form a honeycomb type or a pellet type, the activated carbon carries the nitrogen oxide absorbing component, and the mold material is a honeycomb type or It is a reinforcing material that maintains the pellet mold.

Further, as described above, the mold material is composed of at least one of Ca, Al hydroxide, sulfate, and carbonate, and in particular, slaked lime (calcium hydroxide: Ca (OH) ₂ ) and gypsum (calcium sulfate: CaSO ₄ ) are very preferable in terms of processability, durability, cost, and the like.

  In addition, as said nitrogen oxide absorption component, although alkali salts, such as potassium hydroxide (KOH), can be mentioned, it is not limited to this.

  Further, as described above, the cleaning liquid may be an aqueous solution containing at least one of Ca, Al hydroxide, sulfate, and carbonate. An aqueous solution containing the mold material contained in the base material of the agent, that is, for example, when the mold material is composed of slaked lime and gypsum, There is no adverse effect on the oxide absorbent, which is very preferable.

  The above-mentioned nitrogen oxide absorbent accumulates dust and dirt on the surface with use in a tunnel and the like, and the ability to absorb nitrogen oxide by the absorbing component deteriorates. After being collected, it is immersed in the cleaning liquid for a predetermined time, taken out from the cleaning liquid and dried for drying.

  Subsequently, the nitrogen oxide absorbent is immersed in an aqueous solution of the nitrogen oxide absorbing component, and after the nitrogen oxide absorbing component is held and replenished on the base material, the nitrogen oxide absorbent is taken out from the aqueous solution. Regenerated by drying.

  In the nitrogen oxide absorbent that has been repeatedly cleaned and regenerated using the above cleaning solution in this way, the decrease in strength is remarkably reduced as compared with the conventional case of cleaning using water. The number of times can be greatly increased. The reason for this will be described below.

  As described above, conventionally, when the nitrogen oxide absorbent is repeatedly washed with water, the strength of the nitrogen oxide absorbent decreases, and the nitrogen oxide absorbent can be reused. It was gone. When this cause was investigated, it turned out that the said mold material which comprises the base material of a nitrogen oxide absorber eluted in the water in the case of washing | cleaning, and caused the strength deterioration of the base material.

  Accordingly, the present inventors have developed a nitrogen oxide in which a nitrogen oxide absorbing component is held on a base material containing at least one mold material of at least one of Ca, Al hydroxide, sulfate, and carbonate. In cleaning the absorbent with water, by using water in which at least one of Ca, Al hydroxide, sulfate, and carbonate is dissolved in advance, that is, the cleaning liquid according to the present embodiment. This makes it difficult for the mold material to elute from the base material.

  Therefore, according to this embodiment, the strength reduction of the nitrogen oxide absorbent can be significantly suppressed, and the number of reusable times can be greatly increased.

  In addition, it is very preferable that the cleaning liquid is a saturated aqueous solution containing a saturated state since elution of the mold material from the base material of the nitrogen oxide absorbent can be most reliably suppressed.

  In order to confirm the effect of the cleaning solution of the nitrogen oxide absorbent according to the present invention, the following confirmation experiment was performed.

[Test method]
After forcibly absorbing nitrogen oxide (NO ₂ ) with respect to the nitrogen oxide absorbent, the nitrogen oxide absorbent is washed with a cleaning solution under the conditions shown below, dried to replenish the nitrogen oxide absorbing component, and dried again. The regeneration was repeated (5 times and 10 times), and the rate of change in the crushing strength of the nitrogen oxide absorbent was examined.

[Test conditions]
<Nitrogen oxide absorbent>
・ Shape: Honeycomb type ・ Composition: Activated carbon 27wt%
Slaked lime 47wt%
Gypsum 8wt%
Potassium hydroxide 18wt%

<Cleaning liquid>
{Test 1: the present invention}
An aqueous solution in which a mixture of slaked lime and gypsum in the base material of the nitrogen oxide absorbent (slaked lime: gypsum = 47: 8 = 85.5: 14.5) is dissolved to a saturated state at 20 ° C. { Test 2: Conventional}
Ion exchange water

<NO ₂ absorption conditions>
-Gas used: Air containing 20 ppm of NO ₂ -Temperature: 20 ° C
・ Relative humidity: 60%
Absorption treatment time: 18 hours SV value: 38000 h ^-1

<Washing method>
After being immersed in the cleaning solution for 30 minutes, it is taken out and dried <Regeneration method>
Dry after impregnation with aqueous potassium hydroxide solution

[Test results]
The result of the test performed on the said conditions is shown in FIG.
As can be seen from FIG. 1, in Test 2 (conventional), the strength of the nitrogen oxide absorbent is about 80% compared to the initial value when the cleaning regeneration is repeated 5 times, and the strength of the nitrogen oxide absorbent is repeated 10 times. Compared to the initial value, in Test 1 (invention), the strength of the nitrogen oxide absorbent was higher than that in the case of repeated cleaning and regeneration five times. About 95%, when washing and regeneration was repeated 10 times, it was about 94% compared to the original.

  Therefore, it was confirmed that this invention can suppress the fall of the intensity | strength of a nitrogen oxide absorbent significantly, and can increase the reusable frequency | count significantly.

  The nitrogen oxide absorbent cleaning solution and the nitrogen oxide absorbent cleaning method and regeneration method using the same according to the present invention can remarkably reduce the strength of the nitrogen oxide absorbent and can be reused. Since the number of times can be greatly increased, it can be used extremely beneficially in the industry.

It is a graph showing the effect confirmation test result of the washing | cleaning liquid of the nitrogen oxide absorbent which concerns on this invention.

Claims (5)

Nitrogen oxide absorption in which a base material containing at least one type material of at least one of Ca and Al hydroxide, sulfate, and carbonate holds a nitrogen oxide absorbing component that absorbs nitrogen oxide A cleaning solution for cleaning the agent,
A cleaning solution for a nitrogen oxide absorbent comprising an aqueous solution containing at least one of Ca, Al hydroxide, sulfate, and carbonate. In claim 1,
It consists of the aqueous solution of the said mold material contained in the said base material. The cleaning liquid of the nitrogen oxide absorbent characterized by the above-mentioned. In claim 1 or claim 2,
A cleaning solution for nitrogen oxide absorbent, which is an aqueous solution containing a saturated state. The nitrogen oxide absorbent is cleaned using the nitrogen oxide absorbent cleaning liquid according to any one of claims 1 to 3. A method for cleaning a nitrogen oxide absorbent. The nitrogen oxide absorbent is washed with the nitrogen oxide absorbent cleaning solution according to any one of claims 1 to 3, and then the nitrogen oxide absorbent is impregnated with an aqueous solution of the nitrogen oxide absorbing component. The nitrogen oxide absorbent is regenerated by replenishing the substrate with the nitrogen oxide absorbing component.

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