JPH11267455A - Gaseous hydrogen chloride capturing agent and treatment of acidic waste gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove gaseous hydrogen chloride in an acidic waste gas by fixing and to carry out a treatment free from the elution of fixed chlorine ion. SOLUTION: The treating method is executed by bringing the acidic waste gas into contact with the gaseous hydrogen chloride capturing agent containing a material capable of supplying calcium oxide and silicon dioxide and having a molar ratio CaO/SiO2 of 1.8-2.2 at 600-1500 deg.C to fix gaseous hydrogen chloride. The reaction products, CaO.SiO2 .CaCl2 , are stable and calcium ion or chlorine ion is not eluted even in contact with water.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydrogen chloride gas trapping agent capable of trapping hydrogen chloride gas contained in exhaust gas from a waste incinerator or the like with high efficiency, and an exhaust gas treatment method using the trapping agent. About.

[0002]

2. Description of the Related Art Exhaust gas from an incinerator includes halogenated gas represented by hydrogen chloride (HCl) and hydrogen fluoride (HF), sulfur oxide gas (SOx), nitrogen oxide gas (NOx), and the like. It contains acidic gases, and it is necessary to prevent air pollution caused by these gases. For this reason, after the exhaust gas is cooled to 300 ° C. or lower, it is processed by a dry or semi-dry method of slurry or powder of slaked lime, limestone, etc., and thereafter, a reaction product is collected by passing through a bag filter. . However, in this method, 300 ° C.
There is a problem that hydrogen chloride gas in the acid gas cooled to a low degree reacts with unburned carbon to form highly toxic dioxin.

[0003] For this reason, Japanese Patent Application Laid-Open No. 8-47617 discloses a method for removing hydrogen chloride gas, which is a starting material of dioxin, from exhaust gas. This method
The calcium carbonate particles are brought into contact with high-temperature exhaust gas at 600 to 900 ° C. from an incinerator to form calcium oxide, and the calcium oxide absorbs and fixes an acidic gas component containing hydrogen chloride by the following reaction.

[0004] 2HCl + CaO → CaCl ₂ + H ₂ O 2HF + CaO → CaF ₂ + H ₂ O SO ₂ + CaO → CaSO ₃ SO ₃ + CaO → CaSO ₄

[0005]

However, in the above-mentioned method using calcium oxide, calcium chloride produced by the reaction melts at a high temperature and re-scatters to block an exhaust system such as a flue of an incinerator. Problem has occurred. In addition, it is necessary to secure a landfill disposal site when dust, which is a reaction product with acid gas, is disposed of by landfill. Furthermore, even if it is disposed of at a landfill,
There is also a problem that calcium chloride is eluted from the dust by rainwater, causing salt damage and secondary pollution due to calcium scale.

The present invention has been made in view of such a conventional problem, and it is possible to reliably fix hydrogen chloride gas in an acid gas, thereby obstructing an exhaust system of an incinerator. It is an object of the present invention to provide a hydrogen chloride gas trapping agent which does not cause secondary pollution caused by salt damage or calcium scale, and an exhaust gas treatment method using the trapping agent.

[0007]

To achieve the above object, the hydrogen chloride gas scavenger according to the first aspect of the present invention contains a substance capable of supplying calcium oxide and silicon dioxide,
The O / SiO ₂ molar ratio is in the range of 1.8 to 2.2.

This hydrogen chloride gas scavenger absorbs and immobilizes hydrogen chloride gas with high efficiency by the following reaction.

(2CaO, SiO ₂ ) + 2HCl → Ca
O ・ SiO ₂・ CaCl ₂ + H ₂ O

The reaction product, calcium oxide silicate chloride (CaO.SiO ₂ .CaC)
In l ₂ ), calcium ions and chloride ions do not elute even when contacted with water.

According to a second aspect of the present invention, there is provided the acid gas treatment method, wherein the hydrogen chloride gas scavenger of the first aspect is used in an amount of 600 to 150.
It is characterized in that hydrogen chloride gas is fixed by contacting with acidic exhaust gas in a temperature range of 0 ° C.

According to the present invention, since hydrogen chloride gas is fixed at a high temperature of 600 to 1500 ° C. and removed from the exhaust gas, no dioxin is generated during and after the reaction. The reaction product is stable even at this high temperature and does not melt.

The invention of claim 3 is the invention of claim 2, wherein the hydrogen chloride gas scavenger of claim 1 is sprayed on an incinerator or / and a flue of exhaust gas from an incinerator. And is brought into contact with.

In the present invention, the hydrogen chloride gas is immobilized by spraying the hydrogen chloride gas scavenger onto an incinerator or a flue and contacting the exhaust gas with the exhaust gas. Because of the contact by spraying, the contact efficiency is good, and the hydrogen chloride gas can be efficiently immobilized.

According to a fourth aspect of the present invention, there is provided the second aspect of the present invention, wherein the hydrogen chloride gas capturing agent according to the first aspect is formed into a structure through which a gas can flow, and the formed body is incinerated and / or The exhaust gas from the incinerator is disposed in the flue and is brought into contact with the exhaust gas from the incinerator.

According to the present invention, since the molded article of the hydrogen chloride gas scavenger is disposed in an incinerator or a flue to fix the hydrogen chloride gas, the processing operation is simplified.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The hydrogen chloride gas scavenger of the present invention comprises:
Together comprising a substance capable of supplying calcium oxide and silicon dioxide, the molar ratio of CaO / SiO ₂ is 1.8 to 2.2
Are within the range. The substance that can supply calcium oxide and silicon dioxide may be a substance that simultaneously supplies calcium oxide and silicon dioxide, or may be a combination of substances that individually supply calcium oxide and silicon dioxide. Further, a substance that supplies calcium oxide and silicon dioxide simultaneously, a substance that supplies calcium oxide alone, and a substance that supplies silicon dioxide alone, as appropriate,
They may be combined.

Examples of the substance which simultaneously supplies calcium oxide and silicon dioxide include anhydrous calcium silicate represented by alite and belite, hydrous calcium silicate represented by tobermorite, lime ash, blast furnace slag, and reduced slag. Can be used. The anhydrous calcium silicate has the general formula (CaO) nSiO ₂ , where alite is n = 3 and belite is n = 2.
Hydrous calcium silicate has the general formula (CaO) nSiO
It is a compound of ₂ · mH ₂ O. The substance for simultaneously supplying calcium oxide and silicon dioxide may be one kind or a mixture of two or more kinds.

As the substance capable of supplying calcium oxide alone, one or more of limestone, slaked lime, quicklime, dolomite and the like can be used. Substances that can supply silicon dioxide alone include hydrous silica, anhydrous silica, quartz, tridymite, cristobalite, shirasu,
One or more of pearlite, bentonite and the like can be used.

In the present invention, the molar ratio of CaO / SiO ₂ of the hydrogen chloride gas scavenger is in the range of 1.8 to 2.2. If the molar ratio exceeds 2.2, free CaO increases, and this free CaO reacts with hydrogen chloride gas to generate calcium chloride, which is not preferable. On the other hand, when the molar ratio is less than 1.8, SiO that does not react with hydrogen chloride gas is used.
2 increases, and the effect of capturing hydrogen chloride gas becomes insufficient. Therefore, when combining substances that supply calcium oxide and silicon dioxide alone, they are mixed and adjusted such that the molar ratio of CaO / SiO ₂ is in the range of 1.8 to 2.2. It is a substance or a mixture thereof that supplies calcium oxide and silicon dioxide at the same time.
If the molar ratio of SiO ₂ is not within the range of 1.8 to 2.2 is adjusted by adding the shortage by substance capable of supplying a substance or silicon dioxide may provide the calcium oxide.

The content of CaO in the hydrogen chloride gas scavenger may be 33 wt% or more, and the content of SiO ₂ may be 18 wt%.
It suffices if it is at least wt%. If the amount is less than this, the effect of trapping hydrogen chloride gas will not be sufficient. From the viewpoint of the efficiency of capturing hydrogen chloride gas, more preferably, the content of CaO is 45%.
wt% or more, and the content of SiO ₂ is 25 wt% or more.

The acid gas treatment method of the present invention is to fix the hydrogen chloride gas by bringing the above-mentioned hydrogen chloride gas scavenger into contact with an acidic exhaust gas in a temperature range of 600 to 1500 ° C.

In this treatment method, the contact temperature with the acidic exhaust gas is in the range of 600 to 1500 ° C. When the contact temperature is lower than 600 ° C., the reaction between the hydrogen chloride gas scavenger and the hydrogen chloride gas is delayed, and the trapping rate is reduced,
It is not preferable because hydrogen chloride gas and unburned carbon react to generate dioxin. On the other hand, the contact temperature is 1500 ° C
Is exceeded, CaO, SiO ₂ in the hydrogen chloride gas scavenger
Are partially thermally decomposed and their molar ratios deviate from the above-mentioned ranges, which is not preferable. In addition, there is a possibility that the incinerator or the flue connected to the incinerator may be corroded by an excessively high temperature.

The contact form with the acidic exhaust gas may be incinerator or / and
And by spraying a hydrogen chloride gas scavenger on the flue of the exhaust gas from the incinerator. Alternatively, the hydrogen chloride gas scavenger may be formed into a gas-permeable structure, and the formed body may be disposed in an incinerator or / and a flue of exhaust gas from an incinerator. Further, these contact forms may be used in combination.

When the hydrogen chloride gas scavenger is sprayed, the scavenger is in the form of powder or / and granules. In this spraying, it is preferable to supply CaO and SiO ₂ simultaneously. The powdery and / or granular hydrogen chloride gas scavenger sprayed into the incinerator or / and the flue of the exhaust gas reaches the bag filter together with the exhaust gas from the incinerator and is temporarily stored in the filter. And after treatment for exhaust gas,
Collected from the bag filter and discarded.

The shaped body for shaping the hydrogen chloride gas scavenger into a gas-permeable structure can be in various shapes such as a sphere, a column, a spindle, and a honeycomb. Then, this molded body is used as it is or as a fixed bed filled in a case such as a mesh body or punched metal, and a single bed or a plurality of beds are placed in an incinerator or / and in a flue of exhaust gas from an incinerator, It can be brought into contact with acidic exhaust gas. In this case, it is preferable that the pressure loss is reduced.

By bringing the hydrogen chloride gas scavenger into contact with the acidic exhaust gas at the above-mentioned contact temperature and contact form, the following reaction takes place and the hydrogen chloride gas in the acidic exhaust gas can be fixed.

(2CaO, SiO ₂ ) + 2HCl → Ca
O ・ SiO ₂・ CaCl ₂ + H ₂ O

The calcium oxide silicate chloride (CaO.SiO ₂ .Ca) produced by this reaction
Cl ₂ ) does not elute Ca ions or Cl ions even when it comes into contact with water and is in its crystal lattice, so that even when it is disposed of, no secondary pollution such as salt damage or Ca scale occurs. . The reaction for immobilizing hydrogen chloride gas is 6
Since the treatment is performed at a high temperature of 00 ° C. or more, the incinerator and the like do not corrode at high temperature.

[0030]

EXAMPLES (Example 1) FIG. 1 shows a reaction apparatus for conducting an experiment for trapping gas. This apparatus is mounted so that a quartz tube 2 penetrates a tubular furnace 1 in which a heating element (not shown) is embedded, and a sample 3 is filled in the quartz tube 2. A thermocouple 13 for measuring the temperature of the quartz tube 2 is provided in the tubular furnace 1.
Is attached.

The upstream side of the quartz tube 2 is connected to a gas supply source 5 via a flow meter 4. The upstream side of the quartz tube 2 is also connected to a gas cylinder 7 in which a carrier gas such as N ₂ is stored.
8 is a water bath.

An absorption liquid tank 9 is connected to the downstream side of the quartz tube 2. An absorbing solution 10 for absorbing gas from the quartz tube 2 is stored in the absorbing solution tank 9, and a pH meter 11 for collecting the absorbing solution 10 and measuring the pH is connected to the absorbing solution tank 9, Further, the pH meter 11 includes:
A recorder 12 for recording the measured value is connected.

In this example, 37 g of reagent grade 1 calcium hydroxide (manufactured by Yoneyama Yakuhin Co., Ltd.) and 15 g of reagent grade silicic anhydride (manufactured by Yoneyama Yakuhin Co., Ltd.) were placed in a mortar and mixed while crushing. As a starting sample. 1 g of the starting sample was mixed with 5 g of a granular chamotte for flowing gas, and the mixture was filled in a quartz tube 2 as a sample 3.

Then, N ₂ gas is supplied at a flow rate of 80 ml / min.
The temperature of the quartz tube 2 was raised to 700 ° C. while flowing the solution. The 1 wt% concentration of HCl and a gas mixture of N ₂ when the quartz tube 2 became 700 ° C. was fed into a quartz tube 2 at a flow rate of 50 ml / min. This supply is performed by using the gas discharged from the quartz tube 2 as the absorbing liquid 1.
The absorption was performed at 0 and the pH was monitored with a pH meter 11 until the pH reached 3.5.

Thereafter, when the temperature of the tube furnace 1 reaches room temperature,
The sample 3 was taken out of the quartz tube 2, the chamotte was separated, and the separated chamotte was washed with 100 ml of pure water for 20 minutes while stirring. After this washing, it was subjected to suction filtration and dried to obtain a washed sample. Further, an unwashed sample was used without washing a part of the sample.

The washed sample and the unwashed sample were subjected to X-ray fluorescence analysis using an X-ray fluorescence analyzer (trade name: Rigaku 3270) to measure the contents of Ca, Si and Cl.
Table 1 shows the results. In Table 1 and the following tables, numerical values excluding ratios are% by weight. Further, by diffracting the washed sample with an X-ray diffractometer, the reaction product CaO
- confirmed the peak of SiO ₂ · CaCl _2. FIG. 2 is a characteristic diagram of the X-ray diffraction. In FIG. 2, the peak at the position indicated by the arrow is the peak of CaO.SiO ₂ .CaCl ₂ .

[0037]

[Table 1]

As shown in Table 1, the Ca content and the Cl content of the washed water-washed sample were almost the same as the Ca content and the Cl content of the unwashed sample that had not been washed. It is clear that Ca ions and Cl ions do not elute.

Example 2 In this example, β-type belite ((CaO) ₂ SiO ₂ ) was crushed in a mortar,
1 g thereof and 5 g of Chamotte were mixed, and the mixture was filled in the quartz tube 2 of FIG. Then, the test was performed in the same manner as in Example 1. Table 2 shows the results of the fluorescent X-ray analysis of this example.

[0040]

[Table 2]

Example 3 Tobermorite (5CaO.6)
50 parts by weight of pure water was added to and mixed with 60 parts by weight of SiO ₂ .5H ₂ O) and 100 parts by weight of a mixed powder of 40 parts by weight of slaked lime. Then, after granulating with a disk pelletizer (F-5 type manufactured by Fuji Paudal Co., Ltd.) using a disk having a diameter of 3 mm, the granulated product is dried at 100 ° C. for 5 hours to obtain a cylindrical molded product having a diameter of 3 mm. Obtained. 1 g of this molded product was placed in the quartz tube 2 of FIG.
And tested in the same manner as in Example 1. Table 3 shows the results of the fluorescent X-ray analysis of this example.

[0042]

[Table 3]

Example 4 The weight composition ratios (wt.
%) Of reduced slag and 50 parts by weight of pure water were kneaded, and then granulated in the same manner as in Example 3 to obtain a molded product having a diameter of 3 mm. 1 g of this molded product was filled in the quartz tube 2 of FIG. 1 and tested in the same manner as in Example 1. Table 5 shows the result of the fluorescent X-ray analysis of this example.

[0044]

[Table 4]

[0045]

[Table 5]

[0046]

As described above, according to the hydrogen chloride gas scavenger of the present invention, calcium ions and chloride ions are not eluted even when the reaction product capturing hydrogen chloride comes into contact with water. Therefore, there is no secondary pollution such as salt damage or Ca scale.

According to the acid gas treatment method of the present invention, 60
Since hydrogen chloride gas is fixed at a high temperature of 0 to 1500 ° C., no dioxin is generated during and after the reaction.

[0048]

[Brief description of the drawings]

FIG. 1 is a sectional view of a reactor used for absorbing gas.

FIG. 2 is a characteristic diagram of X-ray diffraction of a reaction product obtained in Example 1.

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[Procedure amendment]

[Submission date] November 12, 1998

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0010

[Correction method] Change

[Correction contents]

[0010] Calcium chlorosilicate (CaO.SiO ₂ .CaCl ₂ ), which is a reaction product, does not elute calcium ions or chloride ions even when it comes into contact with water.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0018

[Correction method] Change

[Correction contents]

Examples of the substance that simultaneously supplies calcium oxide and silicon dioxide include anhydrous calcium silicate represented by alite and belite, hydrous calcium silicate represented by tobermorite, coal ash, blast furnace slag, and reduced slag. Can be used. The anhydrous calcium silicate has the general formula (CaO) nSiO ₂ , where alite has n = 3 and belite has n = 2. Hydrous calcium silicate has the general formula (CaO) nS
It is a compound of iO ₂ · mH ₂ O. The substance for simultaneously supplying calcium oxide and silicon dioxide may be one kind or a mixture of two or more kinds.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0020

[Correction method] Change

[Correction contents]

In the present invention, the hydrogen chloride gas scavenger
CaO / SiO ₂Is in the range of 1.8 to 2.2
It is. When the molar ratio exceeds 2.2, free CaO becomes
This free CaO reacts with the hydrogen chloride gas and
It is not preferable because it generates calcium. Meanwhile, mole
If the ratio is less than 1.8, Si that does not react with hydrogen chloride gas
O₂And the effect of trapping hydrogen chloride gas becomes insufficient.
Therefore, calcium oxide and silicon dioxide are supplied alone
CaO / SiO₂of
Adjust so that the molar ratio is in the range of 1.8 to 2.2.
Mix. Calcium oxide and silicon dioxide are the same.
A substance or a mixture thereof that is sometimes supplied, and its CaO
/ SiO₂Is not within the range of 1.8 to 2.2.
Substances that can supply calcium oxide or carbon dioxide
Adjust for the shortage with substances that can supply iodine
You.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0029

[Correction method] Change

[Correction contents]

The calcium chlorosilicate (CaO.SiO ₂ .CaCl ₂ ) generated by this reaction is
Since Ca ions and Cl ions are not eluted even in contact with water and are in the crystal lattice, secondary pollution such as salt damage and Ca scale does not occur even when disposed.
Further, since the reaction for fixing the hydrogen chloride gas is performed at a high temperature of 600 ° C. or higher, the incinerator and the like do not corrode at high temperature.

Claims (4)

[Claims] 1. A material capable of supplying calcium oxide and silicon dioxide, wherein the molar ratio of CaO / SiO ₂ is 1.8.
A hydrogen chloride gas scavenger characterized by being within the range of -2.2. 2. The hydrogen chloride gas scavenger according to claim 1, wherein
A method for treating an acidic exhaust gas, comprising: contacting the acidic exhaust gas in a temperature range of 00 to 1500 ° C. to fix the hydrogen chloride gas. 3. The hydrogen chloride gas scavenger according to claim 1,
3. The method for treating acidic exhaust gas according to claim 2, wherein the exhaust gas from the incinerator and / or the incinerator is sprayed onto a flue to be brought into contact with the exhaust gas. 4. The hydrogen chloride gas scavenger according to claim 1 is formed into a structure through which a gas can flow, and the formed body is disposed in an incinerator and / or a flue of exhaust gas from the incinerator, and is discharged from the incinerator. The method for treating acidic exhaust gas according to claim 2, wherein the acidic exhaust gas is brought into contact with the exhaust gas.