JP2002273167A - Flue-gas treatment agent and treating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flue-gas treatment agent which does not deteriorate the filterability of a water washed solution when water-washing for the recycling as cement after use, and to provide a method for treating flue gas using the agent. SOLUTION: The agent comprises 1-15% by mass of activated carbon powders of a specific surface area of 1,000 m<2> /g or more and the remainder which is one or more kinds of powders selected from calcium oxide, calcium carbonate and calcium hydroxide as main components.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a flue gas treating agent and a used flue gas treating agent for removing acidic gases such as hydrogen chloride and sulfur oxides and dioxins contained in flue gas from incinerators and the like. The present invention relates to a flue gas treatment method for recycling as a raw material for cement.

[0002]

2. Description of the Related Art Smoke exhausted from incinerators such as refuse incinerators and boilers contains acidic gases such as hydrogen chloride and sulfur oxides and harmful substances such as dioxins, and is one of the main causes of environmental pollution. ing. Various materials have been used as materials for removing such environmental pollutants. For example,
Slaked lime is used as an acid gas absorbent, and activated carbon is used as a dioxin remover. In addition, diatomaceous earth may be added in order to improve the filterability of flue gas with a bag filter installed in a refuse incinerator.

[0003] These flue gas treatment agents are usually blown dry or wet into the flue of the flue gas, react with various harmful substances on the flue or bag filter, and adsorb and remove harmful substances from the flue gas. . The flue gas treatment agent that has adsorbed harmful substances is collected by a bag filter or an electric dust collector, and is discharged from the garbage incineration process as a used smoke emission treatment agent. The spent flue gas treatment agent generated in this way is interim disposed by methods such as solidification of cement, chemical treatment, acid washing or melting, and is then reclaimed at the final disposal site. Due to tightness, it is desired to reduce or reduce fly ash or to recycle it.

[0004] A method of recycling a used flue gas treating agent as a raw material for cement is generated by establishing a distribution route of a product obtained by recycling, ie, cement, or by treating fly ash. There are advantages such as little secondary waste. However, used flue gas treatment agents often absorb hydrogen chloride gas in flue gas and contain chlorine. Chlorine is volatilized in the high-temperature cement kiln and is carried along with the gas to the preheater (preheater) where it condenses and solidifies on the inner surface of the equipment, causing clogging of the preheater and hindering cement production. It is a component which becomes. For this reason, a method has been adopted in which chlorine is removed by washing with water before the used flue gas treating agent is put into a cement firing furnace as a raw material for cement.

[0005]

However, as described above, most of the used flue gas treatment agents in recent years contain activated carbon in order to adsorb and remove dioxins in flue gas.
When this activated carbon is used to wash the used flue gas treatment agent and filter solids, the activated carbon floats in the washing solution and does not settle or clogs the filter cloth, which hinders filtration. was there.

[0006]

SUMMARY OF THE INVENTION The present inventors have found that the use of activated carbon having a specific specific surface area can reduce the content of activated carbon in a flue gas treatment agent, thereby reducing the amount of spent smoke treatment agent used in cement resources. The present inventors have found that it is possible to improve the filterability of a washing liquid when washing with water in order to achieve the present invention, and have completed the present invention.

Specifically, the flue gas treatment agent of the present invention contains 1 to 15% by mass of activated carbon powder having a specific surface area of 1000 m ² / g or more,
The remainder is a flue gas treatment agent containing as a main component at least one selected from calcium oxide, calcium carbonate, and calcium hydroxide. Further, there is provided a flue gas treatment method in which the flue gas treating agent is recovered after use, washed with water to remove salts, and then recycled as a cement raw material.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The flue gas treatment agent of the present invention is characterized by containing 1 to 15% by mass of activated carbon powder having a specific surface area of 1000 m ² / g or more. Activated carbon having a specific surface area of less than 1000 m ² / g does not have sufficient adsorption capacity for dioxins. Therefore, in order to secure a predetermined dioxin adsorption ability, it is necessary to increase the content in the flue gas treating agent. However, the used flue gas treating agent becomes difficult to filter in the washing step. The content of activated carbon is suitably 1 to 15% by mass in the flue gas treatment agent,
More preferably, it is 5 to 10% by mass. If it exceeds 15% by mass, it becomes a used flue gas treating agent and becomes difficult to filter when washed with water. If it is less than 1% by mass, it becomes a used flue gas treating agent and is easily filtered when washed with water, but the adsorbing ability of dioxins is lowered and the ability as a flue gas treating agent is impaired.

The balance other than the activated carbon powder contains, as a main component, at least one selected from calcium oxide, calcium carbonate, and calcium hydroxide. Calcium oxide, calcium carbonate and calcium hydroxide have the effect of absorbing acidic gases such as hydrogen chloride and sulfur oxides in flue gas,
When washing the used flue gas treating agent with water, it also has an effect of supplying calcium ions to the washing solution to enhance the filterability. Calcium oxide, calcium carbonate, and one or more selected from calcium hydroxide as the main component, the calcium oxide, calcium carbonate, and one or more selected from calcium hydroxide is 55% of the remainder other than the activated carbon powder It means that it is contained by mass% or more, and components other than calcium oxide, calcium carbonate, and calcium hydroxide are not particularly limited, but from the viewpoint of recycling as a cement raw material, the constituent components of cement, SiO ₂ , Fe ₂ O ₃ , those containing Al ₂ O _{3 and the} like are preferable. Therefore, as long as it contains 1 to 15% by mass of activated carbon powder and 55% by mass or more of the remainder is at least one selected from calcium oxide, calcium carbonate, and calcium hydroxide, the incinerator bag filter A filter aid such as diatomaceous earth may be used in combination.

The flue gas treating agent in the present invention can be blown in a refuse incineration plant using a conventional flue gas treating agent blowing apparatus as it is. The greater the amount of the smoke exhausting agent blown into the flue, the greater the amount of harmful substances adsorbed and the higher the effect of purifying the smoke exhaust. Injecting a new flue gas treatment agent becomes uneconomical, and increases the amount of used flue gas treatment agent, which has an adverse effect on preserving the remaining capacity of a waste disposal site. Therefore, the amount of the smoke exhaust agent blown depends on the amount of harmful substances generated by refuse incineration and the type of dust collector,
Generally, 1 to ⁵ g per 1 m3 of flue gas is preferred.

The collection and recovery of the used flue gas treating agent which adsorbs and detoxifies harmful substances in the flue gas may be performed by a conventional bag filter or an electric dust collector. The collected used flue gas treating agent is dispersed in water, and the salt adsorbed on the flue gas treating agent is eluted, followed by solid-liquid separation. The solid-liquid separation may be performed by a conventional method using a filter press, a belt filter, or the like. The obtained dewatered cake is used as a part of a cement raw material. The separated filtrate may be subjected to wastewater treatment such as removal of dissolved heavy metals and the like by a conventional method such as an acid-alkali precipitation method, and then drained.

[0012]

The present invention will be described below with reference to examples. (Example 1) Powdered activated carbon having a specific surface area of 1050 m ² / g, calcium hydroxide (JIS R 9001 special name slaked lime) and calcium oxide (JIS R 9001 special name quicklime) were mixed in the ratio shown in Table 1,
A flue gas treatment agent was obtained. This flue gas treatment agent was blown from just before the bag filter of the refuse incinerator, and the dust and the smoke treatment agent were collected by the bag filter to obtain a used smoke treatment agent.
The blowing amount of the flue gas treating agent was 2 g per 1 m ^{3 of} flue gas.
Table 1 shows the measurement results of dioxins in flue gas. 10 kg of water was added to 1 kg of the used flue gas treatment agent, and the mixture was stirred sufficiently. A small one-room filter press (filtration area 0.01 m ² ,
Using a polypropylene filter cloth and air permeability of 1000 ml / cm ² · min), a filtration test was performed according to the method of JIS B 9945 “Testing method for dehydration filtration device”, section 5.15.1. Table 1 shows the measurement results of the dehydration rate. As is clear from Table 1, the concentration of dioxins in the exhaust gas at the outlet of the bag filter was greatly reduced as compared with that at the inlet of the bag filter, and the dehydration rate of the washing liquid was large, which was a practical speed.

(Example 2) Without mixing calcium oxide,
The same procedure as in Example 1 was carried out except that the components other than the activated carbon were calcium hydroxide and were mixed at the ratio shown in Table 1. Table 1 shows the measurement results of dioxins in flue gas and the measurement results of the dehydration rate. As is clear from Table 1, as in Example 1, the concentration of dioxins in the flue gas at the outlet of the bag filter was greatly reduced as compared with that at the bag filter inlet, and the dehydration rate of the washing liquid was high, so that a practical speed was obtained. It was.

(Example 3) As an example of an inorganic powder mainly composed of calcium oxide as a component other than activated carbon, an intermediate raw material of cement extracted from a position at about 1000 ° C. in a cement firing step was used. The procedure was the same as in Example 1 except that the components were mixed in the proportions shown in Table 1. Table 2 shows the components of the inorganic powder containing calcium oxide as a main component. Table 1 shows the measurement results of the dioxins and the measurement results of the dehydration rate. As is clear from Table 1, as in Example 1, the concentration of dioxins in the flue gas at the outlet of the bag filter was greatly reduced as compared with that at the bag filter inlet, and the dehydration rate of the washing liquid was high, so that a practical speed was obtained. It was.

(Comparative Example 1) The same operation as in Example 2 was carried out except that the addition ratio of the powdered activated carbon was reduced and mixed at the ratio shown in Table 1. Table 1 shows the measurement results of dioxins in flue gas and the measurement results of the dehydration rate. As is clear from Table 1, the concentration of dioxins in the exhaust gas at the outlet of the bag filter is:
It did not decrease sufficiently compared to the bag filter inlet.

Comparative Example 2 The procedure of Example 2 was repeated except that powdered activated carbon having a specific surface area of 800 m ² / g was used. Table 1 shows the measurement results of dioxins in flue gas and the measurement results of the dehydration rate. As is clear from Table 1, the concentration of dioxins in the exhaust gas at the outlet of the bag filter was not sufficiently reduced as compared with the inlet of the bag filter.

Comparative Example 3 The same operation as in Example 2 was carried out except that powdered activated carbon having a specific surface area of 800 m ² / g was used, the ratio of powdered activated carbon was increased, and the powdered activated carbon was mixed at the ratio shown in Table 1. Table 1 shows the measurement results of dioxins in flue gas and the measurement results of the dehydration rate. As is clear from Table 1, the concentration of dioxins in the exhaust gas at the outlet of the bag filter was sufficiently reduced as compared with the inlet of the bag filter, but the amount of activated carbon was too large, and the dehydration rate of the washing liquid was extremely low. .

[0018]

[Table 1]

[0019]

[Table 2]

[0020]

According to the present invention, it is possible to maintain the ability to adsorb and absorb harmful substances as usual, and to impair the filterability of the washing liquid when it is washed with cement resources after it has been used. In addition, it is possible to contribute to further reduction of waste through recycling of used flue gas treating agent into cement resources.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B03C 3/01 B03C 3/01 Z 3/02 (72) Inventor Eiji Yamashita 2 Umeda, Kita-ku, Osaka-shi, Osaka −5-25 Taiheiyo Cement Corporation Kansai Branch (72) Inventor Takeshi Tsumi 3-8-1 Nishikanda, Chiyoda-ku, Tokyo Zero Term Division, Taiheiyo Cement Corporation F-term (reference) 4D002 AA02 AA19 AA21 AB01 AC04 BA03 BA04 BA14 DA05 DA11 DA12 DA16 DA41 EA09 FA03 GA01 GB06 GB12 HA06 4D054 AA02 EA02 EA21 EA27 4G066 AA05B AA17B AA43B AE02B BA26 BA42 CA07 CA23 CA31 CA33 DA02 EA13 FA37

Claims (2)

[Claims] 1. A flue gas containing 1 to 15% by mass of activated carbon powder having a specific surface area of not less than 1000 m ² / g, and a balance mainly composed of at least one selected from calcium oxide, calcium carbonate and calcium hydroxide. Processing agent. 2. The flue gas treating agent according to claim 1 is blown into a flue of an incinerator, and a harmful substance is adsorbed and detoxified from the flue gas in the flue and / or on a bag filter. A flue gas treatment method comprising collecting and collecting a smoke treating agent by a bag filter or an electric dust collector, washing the collected flue gas treating agent with water to remove salts, and then recycling it as a cement raw material.