JP2007191670A - System for producing alkaline soil-improving material, combined with flue-gas desulfurization - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To build a system for producing a good-quality alkali soil-improving material in which amount of Ca such as lime used is slight and desulfurization can economically be carried out in high efficiency and unreacted Ca and heavy metal are scarcely mixed, in a dry type fuel-bas desulfurization method suitable for dried areas. <P>SOLUTION: A fluid medium consisting mainly of Ca is fed to the uppermost stage of a multi-stage fluidized bed and the feed is successively moved to the lower stage and flue gas in which fly ash is removed is fed from a gas chamber in the lower part of the lowermost stage and the flue gas is repeatedly brought into contact with the fluid medium in each stage and Ca is substantially completely converted to calcium sulfite or gypsum by SOx in the flue gas while controlling residence time of the fluid medium and then, the calcium sulfite or gypsum is pulled out from the lowermost stage. As a result, flue gas desulfurization is carried out and at the same time, the good-quality soil-improving material scarcely containing a heavy metal and an alkali component is produced. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

本発明は、硫黄含有量の多い石炭の燃焼排煙を乾式で脱硫処理すると同時に、重金属やアルカリ成分が少なくアルカリ土壌の改良に適した良質な土壌改良材を製造するシステムに係わる。  The present invention relates to a system for producing a high-quality soil improvement material suitable for improvement of alkaline soil with few heavy metals and alkali components at the same time as dry-desulfurization treatment of coal flue gas having a high sulfur content.

周知のようにアルカリ土壌は土壌構造が劣化して植物が生育せず、世界の乾燥地域とくに中国などではアルカリ土壌の不毛地帯が膨大な面積を占めている。近年このアルカリ土壌に排煙脱硫で生成する石膏を供給しＮａイオンをＣａに置換して土壌を改良する試みが成果を挙げている。この石膏は硫黄含有量の多い石炭の燃焼排煙の脱硫で得られるが、従来の湿式排煙脱硫法は大量の水を使用するので乾燥地域には適さない。これに対して炉内に直接石灰（ＣａＯ）の微粉を吹き込む乾式排煙脱硫法は簡易ではあるが、石炭中の硫黄分に対して化学量論的に数倍の石灰を吹き込む必要があり不経済であるのみならず未反応で排出される石灰がアルカリ性となるためアルカリ土壌には不適である。また排煙中に含まれる重金属の混入が避けられないので、土壌改良材として長期間供給すれば重金属の蓄積が問題となる。  As is well known, alkaline soil has degraded soil structure and plants do not grow, and in the arid regions of the world, especially in China, barren areas of alkaline soil occupy a huge area. In recent years, attempts have been made to improve the soil by supplying gypsum produced by flue gas desulfurization to this alkaline soil and replacing Na ions with Ca. This gypsum is obtained by desulfurization of coal flue gas with high sulfur content, but the conventional wet flue gas desulfurization method uses a large amount of water and is not suitable for dry areas. In contrast, the dry flue gas desulfurization method in which lime (CaO) fine powder is blown directly into the furnace is simple, but it is not necessary to blow lime several times stoichiometrically with respect to the sulfur content in the coal. Not only is it economical, but the unreacted lime is alkaline, so it is not suitable for alkaline soil. In addition, since heavy metals contained in the flue gas cannot be avoided, accumulation of heavy metals becomes a problem if supplied for a long period of time as a soil conditioner.

上記に対して特許文献１の方法では、水酸化Ｃａを被覆した粒子を流動媒体とする流動層内で排煙を脱硫して石膏とした後に第１の気体固体分離器で生成石膏を流動媒体粒子から分離し、次いで第２の気体固体分離器で石膏粒子をガスから分離回収している。この方法は水の使用量が少なくＣａ利用率が高いという利点があるが、流動媒体粒子は粒子表面の水酸化Ｃａの化学的変化とは無関係な物理的条件に依存して第１の気体固体分離器に吹き上げられるので未反応なＣａ成分の損失を免れないのみならず、気体固体分離器の機能は本質的に気体と固体の分離であって流動媒体粒子からの生成石膏分離は不確実であり、また未反応の水酸化Ｃａが流動媒体粒子から分離して第２の気体固体分離器に達し回収物をアルカリ化する恐れもある。更に、流動媒体としてフライアッシュを利用するとしているが、石炭燃焼のフライアッシュには排煙中の重金属が濃縮されているので、第１の気体固体分離器から流動層に戻されるフライアッシュが流動中に摩滅して流動層を飛び出し第２の気体固体分離器で捕捉されて回収物を重金属汚染する恐れもある。  On the other hand, in the method disclosed in Patent Document 1, the flue gas is desulfurized in the fluidized bed using particles coated with Ca hydroxide as the fluidized medium to form gypsum, and then the generated gypsum is fluidized in the first gas solid separator. The gypsum particles are then separated from the gas by a second gas solid separator, separated from the particles. This method has the advantage that the amount of water used is small and the Ca utilization rate is high, but the fluidized medium particles depend on the physical conditions unrelated to the chemical change of Ca hydroxide on the particle surface and depend on the physical conditions. Not only is the loss of unreacted Ca component unavoidable because it is blown up to the separator, but the function of the gas solid separator is essentially the separation of gas and solid and the gypsum separation from the fluid medium particles is uncertain. In addition, unreacted Ca hydroxide may separate from the fluidized medium particles and reach the second gas solid separator to alkalinize the recovered material. Furthermore, fly ash is assumed to be used as the fluidized medium, but since the heavy metal in the flue gas is concentrated in the coal-burned fly ash, the fly ash returned from the first gas solid separator to the fluidized bed flows. There is also a possibility that the fluidized bed may be worn out and trapped by the second gas / solid separator to contaminate the recovered material with heavy metal.

一方、非特許文献１では、廃コンクリートから砂利などを除いて残った粉末がＣａを主成分としガス中のＳＯｘと数分間で反応して亜硫酸Ｃａとなる知見が報告され、排煙脱硫に利用できる旨の示唆がある。廃コンクリートを破砕して砂利などの有価物を分離回収する技術はすでに国内で数社が実証済みであるから残留粉末の脱硫利用は極めて有意義であるが、実用化するためには可及的に反応時間を短縮しなければならない。  On the other hand, Non-Patent Document 1 reports that the powder remaining after removing gravel and the like from waste concrete has Ca as a main component and reacts with SOx in the gas in a few minutes to become Casulfite, which is used for flue gas desulfurization. There is a suggestion that it can be done. Since several companies have already demonstrated the technology for crushing waste concrete and separating and recovering valuable materials such as gravel, the use of residual powder for desulfurization is extremely meaningful. The reaction time must be shortened.

特開平２００２−１１３３２６「新規脱硫剤による副生物分離可能な脱硫方法および脱硫装置」Japanese Patent Laid-Open No. 2002-113326 “Desulfurization method and desulfurization apparatus capable of separating by-products with a novel desulfurization agent” ２００５年１１月２日日経産業新聞ｐ．１１「火力発電所の排煙脱硫・廃コンクリートを活用」November 2, 2005 Nikkei Sangyo Shimbun p. 11 “Utilizing flue gas desulfurization and waste concrete from thermal power plants”

発明が開発しようとする課題Problems to be developed by the invention

以上に鑑み、本発明は乾燥地域に適する乾式排煙脱硫法で、石灰などのＣａの使用量が少なく経済的・高効率で脱硫でき、且つ未反応なＣａや重金属の混入が少ない良質なアルカリ土壌改良材を製造するシステムを構築しようとするものである。  In view of the above, the present invention is a dry-type flue gas desulfurization method suitable for dry areas, which can be desulfurized economically and efficiently with a small amount of Ca such as lime, and a high-quality alkali with little unreacted Ca and heavy metal contamination It is intended to construct a system for producing soil amendments.

課題を解決するための手段Means for solving the problem

上記課題を解決するための請求項１に記載の発明は、多段流動層では流動媒体粒子の反応が順次各段で均質に行われるので滞留時間を制御すれば未反応の流動媒体粒子の排出を確実に防止できるという多段流動層の利点に着目して発明されたものである。即ち、多段流動層の最上段にＣａを主成分とする流動媒体を供給して順次下段に移動せしめると共に、フライアッシュを除去した排煙を最下段下部のガス室から供給して各段で繰返し流動媒体と接触せしめ、流動媒体の滞留時間を制御してＣａを排煙中のＳＯｘで実質的に完全に亜硫酸Ｃａないし石膏に変換した後に最下段から抜き出すことを特徴としている。  In the invention according to claim 1 for solving the above-mentioned problem, in the multistage fluidized bed, the reaction of the fluidized medium particles is performed homogeneously in each stage sequentially, so that the unreacted fluidized medium particles can be discharged by controlling the residence time. The invention was invented by paying attention to the advantage of a multistage fluidized bed that can be surely prevented. That is, a fluid medium mainly composed of Ca is supplied to the uppermost stage of the multistage fluidized bed and moved to the lower stage sequentially, and flue gas from which fly ash has been removed is supplied from the gas chamber at the lowermost stage, and is repeated at each stage. It is characterized in that it is brought into contact with the fluid medium, and the residence time of the fluid medium is controlled so that Ca is converted into Ca sulfite or gypsum substantially completely with SOx in the flue gas and then extracted from the lowermost stage.

また請求項２に記載の発明は、上記のような固体気体の反応時間を短縮できる多段流動層の利点ならびに非特許文献１の知見に着目して発明されたもので、請求項１の発明において流動媒体が廃コンクリートから砂利などの骨材を分離回収した残りの粉体であることを特徴としている。  The invention described in claim 2 was invented by paying attention to the advantages of the multistage fluidized bed capable of shortening the reaction time of the solid gas as described above and the knowledge of Non-Patent Document 1, and in the invention of claim 1 The fluid medium is the remaining powder obtained by separating and collecting aggregates such as gravel from waste concrete.

また請求項３に記載の発明は、請求項２における流動媒体のＣａ含有量が比較的少ないことならびに流動層が流動媒体粒子の被覆に効果的な特性を有することに着目して発明されたもので、請求項２の発明において多段流動層の最上段若しくはその近傍の流動層内に、補助的に石灰水を撒布して流動媒体を被覆することを特徴としている。  The invention described in claim 3 was invented by paying attention to the fact that the Ca content of the fluidized medium in claim 2 is relatively small and that the fluidized bed has characteristics effective for coating the fluidized medium particles. Thus, the invention according to claim 2 is characterized in that the fluid medium is supplementarily distributed in the fluidized bed in the uppermost stage of the multistage fluidized bed or in the vicinity thereof to cover the fluidized medium.

発明の効果The invention's effect

請求項１の発明によれば、流動媒体粒子は多段流動層内で順次ＳＯｘと反応し各段毎に均質化されるので流動媒体の滞留時間制御が容易となって未反応なＣａの排出を実質的に完全に抑制でき、脱硫効率と経済性が向上する。また予め排煙からフライアッシュを除去しているので重金属の混入も防止できる。即ち本システムによれば、硫黄含有量の多い石炭の燃焼排煙を乾式で高効率かつ経済的に脱硫処理すると同時に重金属やアルカリ成分が少なくアルカリ土壌の改良に適した良質な土壌改良材を製造できる。従って、大気汚染防止のみならず世界の乾燥地域で膨大な面積を占める不毛なアルカリ土壌の改善に寄与し得るものである。  According to the invention of claim 1, the fluidized medium particles sequentially react with SOx in the multistage fluidized bed and are homogenized for each stage, so that the residence time of the fluidized medium can be easily controlled and unreacted Ca is discharged. It is possible to substantially completely suppress the desulfurization efficiency and economy. Moreover, since fly ash is previously removed from the flue gas, heavy metals can be prevented from being mixed. In other words, according to this system, coal combustion flue gas with a high sulfur content is desulfurized with high efficiency and economically, and at the same time, it produces high-quality soil amendments that are low in heavy metals and alkali components and suitable for improving alkaline soil. it can. Therefore, it can contribute not only to air pollution prevention but also to improvement of barren alkaline soil that occupies a huge area in the dry region of the world.

また請求項２の発明によれば、反応効率の高い多段流動層を採用することで請求項１の利点に加えて、廃コンクリートから砂利などの有価物を回収した残りの粉末を排煙脱硫に利用する際の反応時間が短縮されて実用化が容易となり、アルカリ土壌の改善と同時に廃コンクリートの再利用を促進する要因ともなり得る。  Further, according to the invention of claim 2, in addition to the advantages of claim 1 by adopting a multistage fluidized bed with high reaction efficiency, the remaining powder obtained by collecting valuable materials such as gravel from waste concrete is subjected to flue gas desulfurization. The reaction time at the time of use is shortened and it becomes easy to put it to practical use, which may be a factor for promoting the reuse of waste concrete at the same time as improving alkaline soil.

また請求項３の発明は半湿式脱硫に適用する場合であるが、撒布された石灰水が流動媒体を効果的且つ均等に被覆するという流動層の特性を利用して、流動媒体のＣａ含有量が比較的少ない請求項２の発明の欠点を補うことができ、アルカリ土壌の改善と同時に廃コンクリートの再利用を促進し得る。  Further, the invention of claim 3 is a case where it is applied to semi-wet desulfurization, but the Ca content of the fluidized medium is obtained by utilizing the characteristics of the fluidized bed that the distributed lime water covers the fluidized medium effectively and evenly. Therefore, the disadvantage of the invention of claim 2 can be compensated for, and the reuse of waste concrete can be promoted simultaneously with the improvement of alkaline soil.

以下、本発明の実施の形態を図１に基づいて説明する。  Hereinafter, an embodiment of the present invention will be described with reference to FIG.

石炭火力等から排出されるＳＯｘ濃度の高い排煙１を、電気集塵機等の集塵装置２に導いて重金属濃度の高いフライアッシュ３を除去した後にブロワ４で多段流動層５の下部のガス室６に導入し、ガス分散板１４を経て各段で流動媒体７を流動化させて流動層１０を形成せしめる。流動媒体７は、石灰（ＣａＯ）などのＣａ化合物を主成分とする粒子であり、入口回転供給機８を介して多段流動層４の最上段に供給され、各段に連通して設けられた降下管９を通って順次下段に移動し、最下段から出口回転供給機１１を介して排出される。  The gas chamber below the multistage fluidized bed 5 is blown by the blower 4 after the flue gas 1 having a high SOx concentration discharged from coal fired power is guided to a dust collector 2 such as an electric dust collector to remove the fly ash 3 having a high heavy metal concentration. The fluidized medium 7 is fluidized at each stage through the gas dispersion plate 14 to form the fluidized bed 10. The fluid medium 7 is a particle mainly composed of a Ca compound such as lime (CaO), and is supplied to the uppermost stage of the multistage fluidized bed 4 via the inlet rotary feeder 8 and is provided in communication with each stage. It moves to the lower stage sequentially through the downcomer 9 and is discharged from the lowermost stage through the outlet rotary feeder 11.

ここで、図中の入口回転供給機８及び出口回転供給機１１はいずれもシール機能を有する周知の多翼型の回転供給機であり、前者の回転速度を制御し後者を常時回転して生成物を排出させることによって、流動媒体７の供給量すなわち滞留時間を自由に制御することができる。また、各降下管９の上面を各流動層１０の設定上面とほぼ同一とし、各降下管９の下面を各ガス分散板１４の上面より若干離した位置に設定することにより、上部から供給された流動媒体７は流動化に伴って図示矢印のように順次降下し、各流動層１０の上面が自動的に設定値に維持される。  Here, the inlet rotary feeder 8 and the outlet rotary feeder 11 in the figure are both well-known multi-blade type rotary feeders having a sealing function, and are generated by controlling the rotational speed of the former and constantly rotating the latter. By discharging the substance, the supply amount of the fluidized medium 7, that is, the residence time can be freely controlled. Further, the upper surface of each downcomer 9 is made substantially the same as the set upper surface of each fluidized bed 10, and the lower surface of each downcomer 9 is set at a position slightly separated from the upper surface of each gas dispersion plate 14 to be supplied from above. The fluidized medium 7 descends sequentially as shown in the figure with fluidization, and the upper surface of each fluidized bed 10 is automatically maintained at the set value.

以上の構成により、排煙１は重金属を除去された後に流動媒体７と向流で流動接触して高効率で各段毎に順次脱硫され、最上段で浄化ガス１３となって系外に放出される。尚、浄化ガス１３に含まれるダストは周知の手段で捕集還流（図示せず）すればよい。他方、流動媒体７のＣａの反応は順次各段で均質に行われるので、出口回転供給機１１からの排出成分をチェックして未反応なＣａ成分がゼロになるように入口回転供給機８の回転速度を調整して流動媒体７の滞留時間を制御することにより、Ｃａ分は実質的に完全に亜硫酸Ｃａないし石膏に変換されるので、良質な土壌改良材１２を得ることができる。  With the above configuration, the flue gas 1 is removed from the system by removing the heavy metals, and in fluid contact with the fluidized medium 7 in countercurrent, desulfurizing each stage in a highly efficient manner, and becoming the purified gas 13 at the uppermost stage. Is done. The dust contained in the purified gas 13 may be collected and refluxed (not shown) by a known means. On the other hand, since the reaction of Ca in the fluidized medium 7 is performed uniformly in each stage in sequence, the discharge component from the outlet rotary feeder 11 is checked and the unreacted Ca component is zero so that the unreacted Ca component becomes zero. By adjusting the rotation speed and controlling the residence time of the fluidized medium 7, the Ca content is substantially completely converted into Ca sulfite or gypsum, so that a good soil conditioner 12 can be obtained.

上記の操作において、流動媒体７を廃コンクリートから砂利などの骨材を分離回収した残りの粉体とすることができる。即ち、コンクリート廃材を破砕後「加熱すりもみ法」により処理した公開データ例によれば、副産した粉体の粒径は１０〜９０ミクロン程度であり石灰の含有率は２０〜２５％程度に達しているので、運転条件を適切に設定することにより流動媒体７として利用することができる。  In the above operation, the fluid medium 7 can be the remaining powder obtained by separating and collecting aggregates such as gravel from waste concrete. In other words, according to the published data example in which the concrete waste material was crushed and then processed by the “heated surimi method”, the particle size of the by-produced powder was about 10 to 90 microns and the lime content was about 20 to 25%. Therefore, it can be used as the fluid medium 7 by appropriately setting the operating conditions.

また本発明を半湿式法に適用する場合は、図１に示すように、多段流動層５の最上段の流動層１０の内部に撒布ノズル２２を配設して石灰水２１を撒布すれば、流動層の特質上、流動媒体７の表面を効果的且つ均等に被覆することが容易となるので、とくにＣａ含有量が比較的少ない廃コンクリート粉体を利用する場合の弱点を補うことができる。  Further, when the present invention is applied to the semi-wet method, as shown in FIG. 1, if the spray nozzle 22 is disposed inside the uppermost fluidized bed 10 of the multistage fluidized bed 5 and the lime water 21 is sprayed, Because of the characteristics of the fluidized bed, it becomes easy to effectively and evenly coat the surface of the fluidized medium 7, so that it is possible to make up for the weak point particularly when using waste concrete powder having a relatively small Ca content.

本発明の実施形態を示す説明図  Explanatory drawing which shows embodiment of this invention

符号の説明Explanation of symbols

１ 排煙
２ 集塵装置
３ フライアッシュ
４ ブロワ
５ 多段流動層
６ ガス室
７ 流動媒体
８ 入口回転供給機
９ 降下管
１０ 流動層
１１ 出口回転供給機
１２ 土壌改良材
１３ 浄化ガス
１４ ガス分散板
２１ 石灰水
２２ 撒布ノズルDESCRIPTION OF SYMBOLS 1 Smoke exhaust 2 Dust collector 3 Fly ash 4 Blower 5 Multistage fluidized bed 6 Gas chamber 7 Fluid medium 8 Inlet rotary feeder 9 Downcomer 10 Fluidized bed 11 Outlet rotary feeder 12 Soil improver 13 Purified gas 14 Gas dispersion plate 21 Lime water 22 spray nozzle

Claims (3)

多段流動層の最上段にＣａを主成分とする流動媒体を供給して順次下段に移動せしめると共に、フライアッシュを除去した排煙を最下段下部のガス室から供給して各段で繰返し流動媒体と接触せしめ、流動媒体の滞留時間を制御してＣａを排煙中のＳＯｘで実質的に完全に亜硫酸Ｃａないし石膏に変換した後に最下段から抜き出すことを特徴とする、排煙脱硫兼用のアルカリ土壌改良材製造システム。  A fluid medium mainly composed of Ca is supplied to the uppermost stage of the multistage fluidized bed and moved to the lower stage in sequence, and the flue gas from which fly ash has been removed is supplied from the gas chamber at the lower part of the lowermost stage, and the fluidized medium is repeated at each stage. The flue gas desulfurization-use alkali is characterized in that it is extracted from the lowermost stage after being converted into Ca sulfite or gypsum substantially completely with SOx in the flue gas by contacting the fluid medium and controlling the residence time of the fluid medium. Soil improvement material manufacturing system. 流動媒体が、廃コンクリートから砂利などの骨材を分離回収した残りの粉体であることを特徴とする、請求項１に記載の排煙脱硫兼用のアルカリ土壌改良材製造システム。  2. The alkaline soil improvement material production system for flue gas desulfurization according to claim 1, wherein the fluid medium is the remaining powder obtained by separating and collecting aggregates such as gravel from waste concrete. 多段流動層の最上段若しくはその近傍の流動層内に、補助的に石灰水を撒布して流動媒体を被覆することを特徴とする、請求項２に記載の排煙脱硫兼用のアルカリ土壌改良材製造システム。  3. The alkaline soil improvement material combined with flue gas desulfurization according to claim 2, wherein the fluidized bed is coated with auxiliary lime water in the fluidized bed at or near the uppermost stage of the multistage fluidized bed. Manufacturing system.

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