JP2000218131A - Treatment of organaochlorine compound-containing gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inexpensively and effectively treat organochlorine compd.-containing gas generated at a time of the incineration of urban garbage or industrial waste. SOLUTION: At a time of the incineration of waste in an incinerator, a multicomponent oxide type catalyst represented by the general formula; AaBbPcOd (wherein A is at least one element selected from a group consisting of lithium, sodium, potassium, cesium, rubidium, magnesium, calcium, barium, manganese, iron, cobalt, nickel, copper, silver, bismuth, aluminum, gallium, indium, tin, zinc, lanthanum, tungsten, tantalum and niobium, B is at least one element selected from a group consisting of sulfur, boron, silicon and germanium, P is phosphorus, O is oxyden and a, b, c and d are an atomic ratio of respective elements and, when a is set to 1, b is a value of 10 or less containing 0, c is a value of 30 or less not containing 0 and d is a value determined by valencies and an atomic ratio of respective elements) such as AlPO4, Ca3 (PO4) 2 or FePO4 is mixed with waste and the resulting mixture is baked at 200-600 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating a gas containing an organic chlorine-based compound such as dioxins generated during the combustion treatment of waste.

[0002]

2. Description of the Related Art Exhaust gas generated from municipal garbage and industrial waste incinerators usually contains harmful organic chlorine-based compounds such as dioxins, PCBs, and chlorine compounds which are considered to be precursors of these. In particular, it is urgently necessary to establish a technology for removing dioxins from the view that they have a significant effect on living organisms even in very small amounts.

[0003] For example, Japanese Patent Application Laid-Open No. 10-128315 proposes a method in which dioxin compound-containing wastewater is brought into contact with an adsorbent containing acid clay or activated clay to adsorb the dioxin compounds in the wastewater. . In addition, Japanese Patent Application Laid-Open No. Hei 10-151342 proposes an incineration facility that adsorbs dioxins by using a powdery exhaust gas treating agent adsorbent containing an inorganic porous material having a hydrophilic surface. However, such an adsorption treatment method has a problem in treating the adsorbent after adsorbing dioxins.

Further, Japanese Patent Application Laid-Open Nos. 10-66829, 10-99646, and 10-23519
No. 1 proposes a method for removing an organic halogen compound using a VW-TiO ₂ -based catalyst in a fixed bed. However, these fixed-bed catalysts have the problem that, in the case of a large-scale incinerator with a daily incineration capacity of several hundred tons, the construction cost exceeds several hundred million yen and extremely expensive capital investment is required. Having.

[0005]

In view of such circumstances,
The present inventors have conducted intensive studies to find a method that can inexpensively and effectively treat an organic chlorine-based compound-containing gas generated during incineration of municipal garbage and industrial waste, and as a result, use a specific composite oxide-based catalyst. In such a case, it was found that the organic chlorine-based compound in the flue gas could be efficiently and inexpensively processed, and the present invention was completed.

[0006]

That is, the present invention relates to a method for treating an organochlorine compound-containing gas, which comprises treating an organochlorine compound-containing gas generated during incineration by contacting it with oxygen in the presence of a catalyst. General formula AaBbPcO
d (A in the formula is lithium, sodium, potassium, cesium, rubidium, magnesium, calcium, barium, manganese, iron, cobalt, nickel, copper, silver, bismuth, aluminum, gallium, indium, tin, zinc, lanthanum, cerium , Tungsten, tantalum, and niobium represent at least one element selected from the group consisting of sulfur, boron, silicon, and germanium; P is phosphorus, and O is oxygen. And the subscripts a, b, c and d represent the atomic ratio of each element, and when a = 1, b is a value of 10 or less including 0,
c represents a value of not more than 30 not including 0, and d represents a value determined by the valence and atomic ratio of each element. It is another object of the present invention to provide a method for treating a gas containing an organic chlorine-based compound, which comprises using the complex oxide-based catalyst represented by the formula (1).

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. Examples of the exhaust gas to be treated in the present invention include a combustion exhaust gas containing an organic chlorine-based compound such as municipal waste and industrial waste. Such combustion exhaust gas contains dioxins and organochlorine compounds such as chlorobenzenes and chlorophenols, which are precursors thereof.

The composite oxide catalyst used in the present invention is:
This is a composite phosphate catalyst represented by the general formula AaBbPcOd (the symbols in the formula are the same as described above). As the catalyst component A, lithium, sodium, potassium, cesium, rubidium, magnesium, calcium, barium, manganese, iron, cobalt, nickel, copper, silver, bismuth, aluminum, gallium, indium, tin, zinc, lanthanum, cerium, Yttrium, tungsten, tantalum, at least one element selected from the group consisting of niobium, preferably lithium, sodium, potassium, magnesium, calcium, barium, manganese,
It is at least one element selected from the group consisting of cobalt, nickel, aluminum, gallium, indium, tin, zinc, lanthanum, and cerium. Especially in the method of contacting with exhaust gases containing organic chlorine compounds, it is a simple method of mixing and burning with the combustion material without using special equipment, and the catalyst after the treatment of the combustion exhaust gas is landfilled together with residual ash. And at least one element selected from the group consisting of sodium, potassium, magnesium, calcium, and aluminum as the catalyst component A. Use is recommended.

As the catalyst component B, at least one selected from the group consisting of sulfur, boron, silicon and germanium is used.
Species of elements. In the general formula, P represents phosphorus, O represents oxygen, and subscripts a, b, c, and d represent the atomic ratio of each element. When a = 1, b is a value of 10 or less including 0, and c is 0. And d represents a value determined by the valence and atomic ratio of each element. ). When the numerical range indicated by the subscript is out of the above range, a sufficient effect of reducing the amount of the organic chlorine compound in the exhaust gas cannot be obtained.

[0010] The complex phosphate system having such a general formula
Na as a catalyst_TwoHPO_Four, K_TwoHPO_Four, Cs_TwoH
PO_Four, Rb_TwoHPO_Four, MgHPO_Four, CaHP
O_Four, Ca (H_TwoPO_Four)_Two, Ca_Three(PO_Four)_Two, C
aP_TwoO₇, BaHPO_Four, FePO_Four, Co_Three(PO
_Four)_Two, Ni_Three(PO_Four)_Two, Cu_TwoP_TwoO₇, AlP
O _Four, Al (H_TwoPO_Four)_Three, AlH_Three(PO_Four)_Two,
Al_Four(P_TwoO₇)_Three, GaPO_Four, InPO_Four, Sn
_Three(PO_Four)_Two, Zn_Three(PO_Four)_Two, LaPO_Four, C
ePO_FourAnd the like. Especially, Ca_Three(PO
_Four)_Two, AlPO_Four, FePO_FourIs recommended.

The method for preparing the catalyst used in the present invention is not particularly limited, and the catalyst can be prepared by a known method for obtaining a composite oxide catalyst. For example, oxides, hydroxides, nitrates, ammonium salts, carbonates of the elements represented by A and B in the above general formula,
At least one of a chloride, an organic acid salt, an alkoxide, an ammonium metal acid salt and the like, and ammonium phosphate, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, 85
% Phosphoric acid aqueous solution or the like, and then evaporating to dryness, or solid-liquid separation, drying, and firing. For example, in the case of a phosphate catalyst composed of aluminum and phosphorus, an aqueous solution of ammonium phosphate may be added to an aqueous solution of aluminum nitrate, evaporated to dryness, and then fired.

The catalyst may be used alone, but may be supported on a carrier or mixed with a diluent. Examples of the carrier and diluent include boria, silica, alumina, silica-alumina, magnesia, calcia, ceria, zeolite, zirconia, silicon-carbide, clay and the like. There is no limitation on the supported amount or the dilution mixture ratio between the diluent and the catalyst. Further, the catalyst may be used in the form of a powder or may be used after being molded. When molded and used, honeycomb shape,
Known shapes such as a tablet, a ring, a sphere, and a column can be used. The molding method is compression molding, extrusion molding,
A known method such as spray drying granulation may be used.

In practicing the present invention, the catalyst obtained by the above method is treated with an organic chlorine-based compound-containing gas by bringing it into contact with an organic chlorine-based compound-containing gas generated during incineration in the presence of oxygen. As a method of contacting with the compound-containing gas, a fixed bed, a moving bed, a fluidized bed, or the like may be used, and further, it may be put into an incinerator with waste and used. The use temperature of the catalyst of the present invention is not particularly limited. However, if the reaction temperature is too low, sufficient activity cannot be obtained, and if the use temperature is too high, the catalyst may be deteriorated. Therefore, the temperature can be usually selected in the range of 300 to 1000 ° C., preferably 300 to 800 ° C. The reaction pressure can be selected from a wide range from reduced pressure to increased pressure, but is usually in the range of 100 to 400 kPa, preferably 100 to 200 kPa.

[0014]

According to the method of the present invention described in detail above, it is possible to efficiently and inexpensively treat organochlorine compounds in flue gas, especially AlPO ₄ , Ca ₃ (PO ₄ ) ₂ ,
When a composite phosphoric acid oxide catalyst made of FePO ₄ or the like is used, the used catalyst is also buried together with the incineration residual ash,
Alternatively, since it can be used as a raw material for civil engineering and building materials, its industrial effect is extremely large.

[0015]

Next, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples.
In the present invention, monochlorobenzene was used as the organic chlorine compound. Monochlorobenzene (MCB)
Is expressed by the following equation. MCB decomposition rate (%) = (MCB concentration at inlet-MC at outlet)
B concentration) 濃度 (MCB concentration at inlet) × 100

EXAMPLE 1 Calcium nitrate (Ca (NO
₃₎ was dissolved ₂ · 4H ₂ O) _141.70g, and a uniform solution. An aqueous 85% phosphoric acid solution 46.16 was added to this aqueous solution.
g was added with stirring, and the pH was adjusted to 9 using 25% aqueous ammonia. The slurry solution thus obtained was filtered and then dried at 120 ° C. for about 20 hours. The obtained dried product was calcined in air at 500 ° C. for 3 hours to obtain a catalyst. As a result of elemental analysis of this catalyst, the ratio (molar ratio) of phosphorus to calcium was P / Ca = 0.64 [Ca
₃ (PO ₄ ) ₂ ]. This catalyst is pulverized and sieved to 22 to 30
Mesh particles were obtained. 3 g of the catalyst thus obtained and #
18 g of Shinano Random (silicon carbide) manufactured by Shinano Electric Smelting Co., Ltd. were mixed and filled into a Pyrex glass reaction tube having an inner diameter of 15 mm. MCB / CO ₂
/ Oxygen / nitrogen ratio (volume ratio) is 100 ppm / 260
An activity test was performed by supplying a raw material gas consisting of ppm / 15% / 85%. Reaction pressure is normal pressure, space velocity is 5000 /
hr. The MCB concentration at each of the inlet and outlet was analyzed using liquid chromatography. The analysis was performed by the absolute calibration method. As a result, the MCB decomposition rate at a reactor wall temperature of 500 ° C. was 100%.

Example 2 Cerium nitrate (Ce (N) was added to 400 ml of ion-exchanged water.
_{O 3) 3 · 6H 2 O} ) was dissolved 86.95g to prepare a homogenous solution. 23.09 g of 85% phosphoric acid aqueous solution
Was added with stirring, and the pH was adjusted to 9 using 25% aqueous ammonia. The slurry solution thus obtained was filtered, dried, and then calcined in air at 500 ° C. for 3 hours to obtain a catalyst. As a result of elemental analysis of this catalyst, the ratio (molar ratio) of phosphorus to cerium was P / Ce = 0.90 [CePO ₄ ]. The catalyst was pulverized and sieved to obtain 22-30 mesh particles. The activity was evaluated under the same conditions as in Example 1 using this catalyst. As a result, the MCB decomposition rate at a reactor wall temperature of 400 ° C. was 94%.

Example 3 Aluminum nitrate (Al (N
_{O 3) 3 · 9H 2 O} ) was dissolved 150.02g was a uniform solution. An 85% phosphoric acid aqueous solution 46.04 was added to this aqueous solution.
g was added with stirring, and the pH was adjusted to 9 using 25% aqueous ammonia. The slurry solution thus obtained was filtered, dried, and then calcined in air at 500 ° C. for 3 hours to obtain a catalyst. As a result of an elemental analysis of this catalyst, the ratio (molar ratio) of phosphorus to aluminum was P / Al = 0.99 [AlPO ₄ ]. This catalyst is pulverized and sieved to 22-
30 mesh particles were obtained. The activity was evaluated under the same conditions as in Example 1 using this catalyst. As a result, the reactor wall temperature 50
The MCB decomposition rate at 0 ° C. was 96%.

EXAMPLE 4 Iron nitrate (Fe (NO ₃ ) _3.
80.86 g of (9H ₂ O) was dissolved to obtain a uniform solution. 23.06 g of an 85% aqueous phosphoric acid solution was added to this aqueous solution with stirring, and the pH was adjusted to 9 using 25% aqueous ammonia. The slurry solution thus obtained was filtered, dried, and then calcined in air at 500 ° C. for 3 hours to obtain a catalyst. As a result of elemental analysis of this catalyst, the ratio (molar ratio) of phosphorus to iron was P / Fe = 0.98 [FeP
O ₄ ]. The catalyst was pulverized and sieved to obtain 22-30 mesh particles. The activity was evaluated under the same conditions as in Example 1 using this catalyst. As a result, M at a reactor wall temperature of 500 ° C.
The CB decomposition rate was 83%.

Comparative Example 1 In the method of Example 1, the catalyst was Ca ₃ (PO ₄ )
_{In place of 2} , activated alumina having an average particle size of 22 to 30 mesh (trade name BK-112: manufactured by Sumitomo Chemical Co., Ltd.)
The activity was evaluated under the same conditions except for using. as a result,
The MCB decomposition rate at a reactor wall temperature of 500 ° C. was 67%.

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Claims (3)

[Claims] 1. A method for treating an organochlorine compound-containing gas, which comprises treating an organochlorine compound-containing gas generated at the time of incineration by bringing it into contact with oxygen in the presence of a catalyst, wherein the catalyst has the general formula AaBbPcOd (where A is lithium ,sodium,
Potassium, cesium, rubidium, magnesium, calcium, barium, manganese, iron, cobalt, nickel, copper, silver, bismuth, aluminum, gallium, indium, tin, zinc, lanthanum, cerium, tungsten, tantalum, niobium B represents at least one element selected from the group consisting of sulfur, boron, silicon, and germanium;
P represents phosphorus, O represents oxygen, and subscripts a, b, c, and d
Represents the atomic ratio of each element. When a = 1, b represents a value of 10 or less including 0, c represents a value of 30 or less not including 0, and d is determined by the valence and atomic ratio of each element. Represents a value. A method for treating a gas containing an organic chlorine-based compound, which comprises using the complex oxide-based catalyst represented by the formula (1). 2. The catalyst component A of the complex oxide-based catalyst represented by the general formula AaBbPcOd comprises at least one element selected from the group consisting of sodium, potassium, magnesium, calcium, barium and aluminum. The method for treating a gas containing an organic chlorine-based compound according to claim 1. 3. The method for treating a gas containing an organic chlorine-based compound according to claim 1, wherein the catalyst is present in a state of being mixed and stirred with the incineration material in the incinerator.