WO2005030641A1

WO2005030641A1 - Highly activated coke powder and process for producing the same

Info

Publication number: WO2005030641A1
Application number: PCT/JP2003/012355
Authority: WO
Inventors: Yukihiro Hirabayashi; Yuuji Horikawa; Masao Sotooka; Hiroyasu Nishiyama; Mitsuaki Shiiya; Hisao Tsuboya; Kazunori Kandani
Original assignee: Electric Power Development Co., Ltd.
Priority date: 2003-09-26
Filing date: 2003-09-26
Publication date: 2005-04-07
Also published as: AU2003266652A1

Abstract

A highly activated coke powder comprising abraded particles separated from regenerated activated coke particles having heightened activity imparted by adsorption and thermal desorption of sulfur oxides in a dry flue-gas desulfurization process, characterized by having been regulated in particle size so that the average particle diameter is 10 to 15 µm and the content of particles having a particle diameter of 0.3 to 4 µm is 10 to 25 wt.% based on the whole particles. The coke powder can efficiently adsorb the dioxins, mercury, and other heavy metals contained in discharge gases to make the gases harmless. The powder can be provided at low cost because it comprises regenerated activated coke particles.

Description

Highly activated coke powder and method for producing the same

The present invention relates to a highly activated coke powder and a method for producing the same, and more particularly to a highly activated active coke powder which is effective as a spray for adsorbing dioxins, mercury, and other heavy metals discharged from waste incinerators and the like. The present invention relates to coke powder and a method for producing the same.

book

Background art

Sulfur oxides, nitrogen oxides, etc. are contained in flue gas discharged from boilers and other heating combustion furnaces that use sulfur-containing pulverized coal, coal-based or petroleum-based heavy oil, etc. as a fuel source. Contains air pollutants. As a method for desulfurization and denitration of combustion exhaust gas containing such sulfur oxides and the like, the combustion exhaust gas is contact-washed with an alkaline aqueous wet absorbent such as an aqueous aluminum hydroxide solution and an aqueous ammonia solution to remove sulfur oxide and the like. A wet flue gas desulfurization method that absorbs and removes water, or a dry flue gas desulfurization method that makes contact with activated coke to adsorb sulfur oxides is used.

In the dry flue gas desulfurization method using activated coke, the flue gas is introduced into a moving bed type adsorption tower filled with activated coke particles to remove harmful substances such as sulfur oxides contained in the exhaust gas. The particulate matter is adsorbed and removed, and the exhaust gas after being adsorbed and removed is discharged to a chimney directly or through a dust collector. On the other hand, activated coke particulates that have adsorbed harmful substances are recycled by heating and regenerating, and sulfur oxides and the like separated by the heating and regenerating treatment are oxidized by a recovery device to form concentrated sulfuric acid and reduced sulfur. Collected as a by-product. The abrasion powder generated by the regeneration process is either incinerated or processed together with fly ash as a raw material for cement.

On the other hand, municipal waste incinerators, combustible waste treatment furnaces, and waste incinerators for metal refining plants There are trace amounts of dust and organic compounds that contain heavy metals such as mercury in the combustion waste gas emitted from such sources. Here, dioxins represented by polychlorinated dibenzodioxin (PCDD), polychlorinated dibenzofuran (PCDF), and cobrana PCB among organic compounds are attracting attention as harmful substances to the human body. Law etc.) are being prepared. Despite the improvement of combustion conditions in accordance with the structural standards set by these laws and regulations, dioxins re-synthesize (denopo-synthesis) mainly in the temperature range of 200 ° C to 350 ° C, and dioxin concentration It has been reported that problems such as an increase in the number of occurrences occur.

As a method for removing such dioxins, a dry method is used in which the exhaust gas discharged from the incinerator is sequentially introduced into a bag filter and an activated coke adsorption tower to remove soot, harmful substances and odorous substances contained in the exhaust gas. Many are known. In this case, dioxins, precursors of dioxins, hydrogen chloride and the like are removed by adsorption or reaction by spraying activated coke powder into the exhaust gas prior to introducing the exhaust gas to the bag filter. The activated coke (or activated carbon) powder to be sprayed here is desirably a highly activated powder that uniformly disperses and floats in the exhaust gas stream and simultaneously adsorbs harmful substances such as dioxins and heavy metals. Such commercially available activated coke powder is inevitably expensive, and the continuous consumption of a large amount of the activated coke increases the running cost. Excellent and cheaper ones are desired.

Therefore, prior to directing the exhaust gas from the municipal garbage incinerator to the bag-fill evening, Japanese Unexamined Patent Application Publication No. 9-129046 discloses that a scattered adsorbent is blown into the exhaust gas stream to remove harmful substances in the exhaust gas. A method has been proposed that adsorbs, separates and removes dust and scattered adsorbent in a bag filter, guides the exhaust gas that has exited the bag filter to an activated coke adsorption tower, and adsorbs and removes harmful substances remaining in the exhaust gas with an adsorbent. . Also, Japanese Patent Application Laid-Open No. 1-16-169664 discloses that a carbonaceous adsorbent is blown into an exhaust gas stream after dust has been removed at a bagfill, and then the carbonaceous adsorbent is transferred to a moving bed reactor. Harmful substances to carbon A method of adsorbing and removing with a porous adsorbent has also been proposed. In both of these proposals, the activated coke (carbonaceous adsorbent) extracted from the adsorption tower is heated and regenerated in the regeneration tower, and the regenerated activated coke is returned to the adsorption tower via a sieving device and recycled. It is characterized in that the waste activated coke powder separated from activated coke in the sieving apparatus is used as it is as a spray adsorbent or a carbonaceous adsorbent in the same process.

However, the waste activated coke powder used as a spray adsorbent or a carbonaceous adsorbent in the above proposed method is cheaper and more advantageous than a commercial product in that it uses what has been conventionally treated as waste. Because particle size is not adjusted, it is difficult to uniformly disperse and float in the exhaust gas stream, and because it is reused in the same dioxin and other exhaust gas treatment equipment, the increase in pore volume is small and it is useful for adsorbing dioxin again. There is a drawback of low activation activity. Furthermore, there is a limit to the amount of waste activated coke that can be used separately from the same process, and it can cover only the required blowing amount of about 1 Z5 to 1 Z2. Therefore, there is a strong demand for the development of an inexpensive and highly active activated coke powder that eliminates the drawbacks of vigorous activity.

In view of the above situation, an object of the present invention is to provide an inexpensive and highly activated activated coke powder capable of efficiently adsorbing and detoxifying dioxins contained in exhaust gas, and a method for producing the same. .

Disclosure of the invention

As a result of various studies on the above-mentioned problems, the present inventors have found that the abrasion powder generated during heating and regeneration of activated coke granules used in the flue gas desulfurization process of flue gas, in particular, has an increased pore volume. It has been found that the activation activity can be increased by adjusting the particle size, and that it can be optimally used as a spray for adsorbing dioxins in a dioxin-containing exhaust gas treatment process, and has led to the present invention. is there.

That is, the highly activated coke powder and the method for producing the same according to the present invention have the following structure or Or a means for solving the above-mentioned problems.

The highly activated coke powder of the present invention comes in contact with a sulfur oxide-containing combustion exhaust gas in a dry flue gas desulfurization process to adsorb sulfur oxides and the like, and the activated coke powder is heated and desorbed to increase the activation, thereby regenerating activated coke powder. It is a wear powder separated from the particulate matter. And the high activation activity coke powder of the present invention is such that the abrasion powder has an average particle diameter of 10 to 15 m, and a content of 0.3 to 4 m in the total content of 10 to 15 m. It is characterized in that the particle size has been adjusted to 25% by mass.

In the highly activated activated coke powder of the present invention, the pore volume has been increased by repeating the adsorption and heating desorption treatment of sulfur oxides present in gaseous form in flue gas. Adsorption performance is the most improved because of the use of abrasion powder from waste. Furthermore, because of its excellent uniform dispersion and floating properties in the exhaust gas stream due to particle size adjustment, it can exhibit high adsorption performance on large molecular diameter substances such as sulfur oxides, dioxins, and heavy metals such as mercury.

In addition, the highly activated coke powder of the present invention contains dioxins and heavy metals such as mercury contained in exhaust gas discharged from a waste incinerator or the like and cooled to 190 ° C or less. Preferably, it is used as a spray for adsorption.

According to the present invention, since it is used in an exhaust gas treatment process containing dioxins, which is different from the dry flue gas desulfurization process, it is possible to cope freely without a shortage of a desired blowing amount. In addition, the coke powder adsorbing dioxins has a low dust loss due to a small pressure loss at the bag filter and easy passage through the bag filter filtration surface due to the above particle size adjustment. Does not inhibit. Furthermore, since the high ignition resistance of activated coke (ignition temperature 450 ° C or higher) is inherited, the captured fine powder exerts the effect of preventing ignition of bagfill.

The method for producing highly activated coke powder of the present invention is a dry method in which a combustion exhaust gas containing sulfur oxide is introduced into an adsorption tower filled with activated coke particulates as an adsorbent to adsorb and remove sulfur oxide and the like. Activity of adsorbing sulfur oxides etc. in flue gas desulfurization process The coke granules are heated to 400 ° C to 600 ° C in an inert gas atmosphere to be regenerated and circulated to the adsorption tower. It is characterized in that the average particle diameter is 10 to 15 m, and the content of the particles having a particle diameter of 0.3 to 4 m is adjusted to a particle size of 10 to 25% by mass of the whole. According to the above manufacturing method, abrasion powder that has been generated in large quantities in the dry flue gas desulfurization process (about 200,000 tons per year at coal-fired power plants with a power generation output of 600,000 KW) Has been incinerated as a fuel auxiliary material in a boiler, or has been treated as a raw material for cement with fly ash. Ix flour is obtained as an inexpensive by-product. As a result, the purchase and use of expensive commercial activated carbon powder is greatly reduced, and excellent economic effects can be achieved as a substitute. Brief Description of Drawings

The first is a schematic process flow diagram of a dry flue gas desulfurization method of flue gas used for producing the highly activated coke powder of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described in detail.

The flue gas used in the dry flue gas desulfurization process used to produce the highly activated coke powder of the present invention is sulfur-containing pulverized coal, coal-based or petroleum-based heavy oil, or the like. Combustion exhaust gas discharged from combustion furnaces such as boilers of large thermal power plants and various industrial heating furnaces, which contain little dioxins but are not gaseous sulfur oxides or It contains nitrogen oxides and the like, and is usually cooled to about 150 ° C to 100 ° C by heat recovery cooling means. In particular, the combustion exhaust gas from a boiler heating furnace of a large thermal power plant, which generates a large amount of combustion exhaust gas, is preferable in that the high activation activated coke powder of the present invention can be obtained in a large amount. The activated coke (or activated carbon) particulate used for the adsorption of sulfur oxides and the like in the combustion exhaust gas is not particularly limited as long as it has been conventionally used in a dry flue gas desulfurization method. It is sufficient that the pellet has a shape of a spherical pellet to a cylindrical pellet, and a cylindrical pellet having a diameter of 1011] and a length of 10 mm is particularly desirable. Generally, such activated coke or activated carbon is obtained by treating wood, lignite, peat, coconut husk, etc. with chemicals (such as zinc chloride and phosphoric acid) as an activator and carbonizing, or activating charcoal with steam. A commercially available granulated product manufactured by the above method is used. Here, an example of the dry flue gas desulfurization method of the combustion exhaust gas of the present invention in which the abrasion powder for specifying the highly activated coke powder is separated will be described with reference to FIG.

In general, the combustion exhaust gas 1 discharged from a combustion furnace using a fuel such as sulfur-containing coal or heavy oil is recovered by a boiler or the like (not shown) to be 37 0 to 38 0 C, and is further preheated by air. After being cooled to 150 to 100 ° C by a heat recovery means such as a vessel, it is introduced into the dry flue gas desulfurization process. That is, the flue gas 1 is introduced from the lower part of the moving bed type desulfurization tower 2 in which activated coke (or activated carbon) particulate matter is filled as the adsorbent, and the adsorbent moving bed descends. The harmful substances such as sulfur oxides contained in the combustion exhaust gas are adsorbed and removed by the adsorbent by direct contact with the exhaust gas. At this time, ammonia gas 3 can be injected into the flue gas to be introduced, if necessary, to enhance the effect of adsorbing and removing harmful substances. The flue gas after the adsorption removal treatment is discharged to the chimney 5 directly from near the upper part or after collecting dust by the dust collector 4.

On the other hand, the activated coke particulates adsorbing harmful substances continuously discharged from the bottom of the desulfurization tower 2 are sent from the transfer line 6 to the regeneration tower 7. In the regenerator 7, the activated coke adsorbing harmful substances by the hot air from the hot blast stove 8 is indirectly heated to 400 to 600 ° C (450 ° C), and the inert gas such as N2 gas is carried by the carrier gas. And the sulfur oxides are desorbed. The desorbed sulfur oxide is sent from the line 9 to the recovery unit 10 where it is oxidized and recovered as concentrated sulfuric acid by-product 11 or as a sulfur by-product by a reducing agent. Regeneration active core from which sulfur oxides etc. have been desorbed After being cooled in the lower part of the regenerating tower 7, it is extracted and separated into regenerated active coke granules 13 and abrasion powder 14 having a diameter of 1 mm or less by the sieve device 12. The sieve mesh of the sieve device 12 is not particularly limited, but it is usually desirable to separate abrasion powder having a size of l mm or less.

The regenerated activated coke granules 13 remaining on the sieving apparatus are appropriately mixed with a new activated coke replenisher from the circulation line, returned to the desulfurization tower 2, and recycled for reuse. On the other hand, abrasion powder 14 of 1 mm or less that passed through the sieving device was conventionally incinerated as a fuel auxiliary material in a boiler or treated as a cement material together with fly ash. In the present invention, the abrasion powder under the sieving apparatus is transferred from the line 14 and stored in the storage opening 15 as appropriate. The abrasion powder is classified by a sieve device or an air classifier (not shown) to adjust the particle size to a specific range, whereby the highly activated coke powder of the present invention can be obtained. When the particle size is adjusted by the classification process, the abrasion powder removed from the specific range may be appropriately ground and used by the classification process, or may be granulated and recycled together with the regenerated coke.

In particular, in the present invention, the average particle diameter of the wear powdery material of 1 mm or less is 10

It is characterized in that the particle size is adjusted to about 15 to 15% by mass, preferably about 15 to 15% by mass, with a content of im15 im and a particle size of 0.3 to 4 m. Abrasion powder without particle size adjustment, as it is, cannot be used as a spray for adsorbing dioxins contained in exhaust gas. If the removal rate of adsorption is reduced and ultra-fine powder of 0.3 m or less is contained, it is not preferable from the viewpoint of air pollution because it easily passes through the bag filter. In order to use the powder as a spray for dioxins adsorption, dioxin-containing exhaust gas discharged from a conventionally known waste incinerator etc. must be introduced sequentially into a bag filter and an activated coke adsorption tower. It is desirable to use a dry method to remove soot, harmful substances and odorous substances contained in exhaust gas. this In this case, it may be sprayed at the line before introduction of the exhaust gas flow into the bag filter, or may be sprayed at the outlet line of the pug filter. Preferably, it is desirable to use it as a propellant for adsorption of dioxins in a line before introduction into a bag filter. The highly activated coke powder of the present invention has an increased pore volume due to the repeated adsorption and heating desorption of sulfur oxides present in gaseous form in the combustion exhaust gas. Adsorption performance is most improved due to the use of abrasion powder from the coke surface, and dioxin adsorption performance is extremely high, so most dioxins are adsorbed and removed in the bag filter introduction line. Therefore, it may be discharged directly to the chimney without passing through the activated coke adsorption tower.

Next, the present invention will be described in more detail by way of examples. The present invention need not be limited to the following embodiments.

The methods for measuring dioxins and mercury used in the following Examples are shown below. * Measuring method of dioxins: JIS K 0 3 1 1 According to the provisions of “Method of measuring dioxins and cobraner PCB in exhaust gas”.

* Measurement method of mercury: JIS K 0 2 2 2 According to the provisions of “Method for analyzing mercury in exhaust gas”.

Example 1

(Production of highly activated coke powder)

At a coal-fired power plant (power output 600,000 KW), the flue gas from a poiler combustion furnace using pulverized coal as fuel is cooled to 140 ° C or less via an air preheater, and then activated coke granular Material (diameter: 10 mm Φ 円筒 length: 10 mm, cylindrical pellet) is introduced into a moving bed type adsorption tower filled with adsorbent, and sulfur oxides are adsorbed and removed by the adsorbent. In a dry flue gas desulfurization process in which dust is removed and then discharged into a chimney, activated coke particulates, which have adsorbed sulfur oxides and the like in an adsorption tower, are heated by a hot gas from a hot blast stove under the accompanying carrier gas (N2 gas). Regeneration by indirect heating to around 450 ° C After being cooled, it is classified by a vibrating sieve. Here, the sieve on the screen of lmm or more was circulated to the adsorption tower, and at the same time, powdered material under the sieve of less than 1 mm was extracted. At this time, the average particle diameter of the under-sieve abrasion powder and the like was about 20 zm, and the content of the particle diameter of 0.3 to 4 _m was 10% by mass or less (% by mass) of the whole. This was subjected to an airflow classifier, and the particle size was adjusted by classification so that the average particle diameter was 13.8 nm and the content of particles having a particle diameter of 0.3 to 4 mm was 18.1% by mass of the whole. A highly activated coke powder was obtained.

(Dioxins removal performance test)

Activated coke powder is blown into the exhaust gas line from a waste combustion furnace for small poilers using dry pelletized products (RDF) such as garbage waste as a fuel source, guided to a bag filter for dust collection, and then discharged directly to the chimney In the exhaust gas treatment device, the highly activated coke powder of the present invention obtained above was introduced into the exhaust gas stream adjusted to 170 to 180 ° C just before the bagfill, (1) 150 mg / Nm ³ DRY, (2) ) 220mg / Nm ³ D

RY, (3) 320 mg / Nm ³ DRY blow-in at three different blowing rates, and dioxins typified by polychlorinated dibenzodioxin (PCDD) are discharged into the exhaust gas flow before the injection of active coke powder. Of dioxins and heavy metals typified by mercury in the air and the same content in the exhaust gas stream at the bag filter outlet after the injection of activated coke powder

The removal rate is determined according to the provisions of JIS K0311 and JIS K0222, respectively. From this, the removal rate is set to {(1—outlet content / inlet content) × 100}. The results are shown in Table 1. The passability of the activated coke powder through the bag filter (particle size 0.3 m or less) was 0% by mass.

Comparative Example 1

Instead of the high activation activated coke powder used in Example 1, classification treatment was not not undersize wear powder-like product ^{(1) 150mg / Nm 3 DRY} , (2) 200mg / Nm 3 DR Y, (3) 32 Omg / Nm ³ DRY is injected at three different injection rates to obtain dioxins represented by polychlorinated dibenzodioxins (PCDD) and mercury represented by mercury The removal rate of heavy metals to be removed was measured. The results are shown in Table 1. The passability of the activated coke powder through the bag filter (particle size: 0.3 zm or less) was also 0% by mass.

Reference example 1

In place of the highly activated coke powder used in Example 1, a commercially available spray agent for adsorbing dioxins (having an average particle diameter of 13.2 zm and a content of 0.3 to 4 zm in particle diameter) was used. total 22 2.3 wt% (mass ^{percentage)) (1) 150mgZNm 3 D} RY, (2) 200mg / Nm 3 DRY, by blowing in three blow amount of ⁽³⁾ 320 mgZNm 3 DRY, polychlorinated The removal rates of dioxins represented by dibenzodioxin (PCDD) and heavy metals represented by mercury were measured. The results are shown in Table 1. The passability of the activated coke powder through the bag filter (particle diameter 0.3 m or less) was 0% by mass.

table 1

As is clear from the results shown in Table 1, the highly activated coke powder of the present invention has a dioxin removal rate of 98 to 99% and a heavy metal (mercury) removal rate of 92 to 97%. It can be seen that the removal rate of the commercial product is superior to that of the commercial product. On the other hand, the under-sieved abrasion powder that had not been classified has an unstable dioxin removal rate of 82 to 90% and a heavy metal (mercury) removal rate of 87 to 94%, which is lower than that of commercial products. Note that The fine powder passing through the filter (particle size: 0.3 m or less) was 0% by mass. Incidentally, blowing amount of the high activation activity co one box powder, 1 5 O m gZNm ³ at a sufficient it can be seen that no improvement effect can be enhanced more. Industrial applicability

The highly activated coke powder of the present invention has improved pore volume and adsorption performance by repeating adsorption and heating desorption of gaseous sulfur oxides in flue gas. It exhibits excellent adsorption performance to large molecular substances such as sulfur oxides and dioxins because of its excellent uniform dispersion and floating properties. In addition, simply adding a classification process to the abrasion powder that has been generated in large quantities in the dry flue gas desulfurization process makes it possible to obtain highly activated coke powder with increased added value easily. As a result, the purchase and use amount of expensive commercial activated carbon powder is greatly reduced, and a superior economic effect is exhibited by using a substitute, thereby increasing industrial applicability.

Claims

1. Abrasive powder separated from regenerated activated coke granules that have been contacted with the combustion exhaust gas in the dry flue gas desulfurization process and have been activated by heat desorption treatment, and have an average particle size of 10 to 15 X m A highly activated coke powder characterized in that the content of the particles having a particle diameter of 0.3 to 4 ^ m is adjusted to a particle size of 10 to 25% by mass.

Contract

2. A patent claim for use as a propellant for the adsorption of dioxins, mercury and other heavy metals contained in flue gas discharged from waste incinerators and cooled to 190 ° C or less. 2. Highly activated coke powder according to claim 1.

3. Sulfur oxide-containing combustion exhaust gas is introduced into an adsorption tower filled with activated coke particulates as an adsorbent to adsorb and remove sulfur oxides in a dry flue gas desulfurization process in which sulfur oxides are adsorbed and removed. The activated coke granules thus obtained are heated to 400 ° C. (: up to 600 ° C.) in an inert gas atmosphere, regenerated, and circulated to the adsorption tower. The average particle diameter is 10 to 15 m and the particle size is 0.3 to 4 m, and the particle size is adjusted to 10 to 25 mass% of the whole by classification. A method for producing highly activated active coke powder.

4. The highly activated coke powder according to claim 3, wherein the sulfur oxide-containing combustion exhaust gas is a combustion exhaust gas discharged from a boiler combustion furnace of a thermal power plant using coal powder as a fuel source. Production method.