報告書番号

U92001

タイトル（和文）

石炭の生物加工－５－鉄酸化細菌の浮遊選炭への応用とその脱硫効果

タイトル（英文）

DEVELOPMENT OF MICROBIAL COLUMN FLOTATION FOR COAL DESULFURIZATION

概要 （図表や脚注は「報告書全文」に掲載しております）

微生物を用いた石炭の燃焼前脱硫法の開発を目的とし，浮遊選炭への鉄酸化細菌の応用を試みた。浮遊選炭では，石炭と無機硫黄は，ともに水をはじく性質なので気泡に付着して浮き上がりそれぞれを分別できない。しかし，細菌を加えることにより、無機硫黄は、表面が水をはじく性質から水になじむ性質に変わり気泡に付着しなくなり１分間のうちに除去された。これにより脱硫時間を，従来の微生物を用いた浸出脱硫法の１～２週間から大幅に短縮できた。この条件下で，高硫黄炭を模擬した石炭から無機硫黄の７０％を脱流できた。また，この細菌を用いた浮遊選炭の脱硫機構の解明を行った。

概要 （英文）

COAL HAS GOTTEN INCREASING ATTENTION AS A MORE IMPORTANT ENERGY RESOURCE THAN OIL. HOWEVER,COAL CONTAINS SULFUR WHICH IS RELEASED AS SULFUR DIOXIDE INTO THE ENVIRONMENT. TO CUT EMISSIOS OF SULFUR DIOXIDE,SULFUR IS REMOVED AFTER COMBUSTION BY FLUE-GAS DESULFURIZATION SYSTEMS. IN RECENT YEARS, MICROBIAL DESULFURIZATION HAS BEEN PROPOSED AS A COST-EFFECTIVE PIE-COMBUSTION DESULFURIZATION TECHNIQUE. HOWEVER,CONVENTIONAL MICROBIAL DESULFURIZATION TAKES ONE OR TWO WEEKS. FOR MASS COAL DESULFURIZATION,THE DESULFURIZATION PERIOD MUST BE SHORTER. THIS PAPER REPORTS MICROBIAL TREATMENT USING THIBACILLUS FERROOXIDANS (ATCC23270) IN COLUMN FLOTATION. BOTH PYRITE AND COAL ARE HYDROPHOBIC,SO FLOTATION IS INEFFECTIVE AS A METHOD FOR SEPARATING PYRITE FROM COAL. AIR BUBBLES ATTACH TO BOTH BECAUSE OF SIMILAR SURFACE PROPERTIES ANDTHEY FLOAT TOGETHER. BUT ADDITION OF BACTERIA TO FLOTATION CAN SEPARATE PYRITE FROM COAL IN JUST A FEW MINUTES. THE BACTERIA CHANGE THE PYRITE SURFACE PROPERTIES FROM HYDROPHOBIC TO HYDROPHILIC AND PREVENT AIR BUBBLES ATTACHING TO THE PYRITE. THE INFLUENCE OF THE BACTERIA DENSITY INTHE FLOTATION LIQUOR ON PYRITE FLOTATION WAS INVESTIGATED. THERE IS A LINEAR CORRELATION BETWEEN THE REDUCTION OF FLOATING PYRITE AND THE NUMBER OF BACTERIA ADHERING TO PYRITE. THE LINEAR CORRELATION SHOWS THAT THE BACTERIAL COVERAGE ON THE SURFACE IS DIRECTLY RELATED TO PYRITE FLOATABILITY. IN ADDITION BACTERIA WITH NO IRON-OXIDIZING ACTIVITY AS A RESULT OF TREATMENT WITH SODIUM CYANIDE ALSO ADHERED TO PYRITE AND REDUCEDTHE PYRITE FLOAT ABILILG AS QUICKLY AS UNTREATED BACTERIA. THE PYRITE SURFACE CHANGE FROM HYDROPHOBIC TO HYDROPHILIC IS CAUSED BY QUICK ADHESION OF BACTERIA TO THE PYRITE SURFACE RATHER THAN BY OXIDATION. A COAL/PYRITE MIXTURE WAS USED IN A MICROBIAL FLOTATION COLUMN TO SIMULATE HIGH-SULFUR COAL. THE DESULFURIZATION EFFECT WAS RELATED TO THE DENSITY OFTREATED BACTERIA AND TO THE PYRITE PARTICLE SIZE.A BACTERIAL DENSITY IN THE FLOTATION LIQUOR OF LESS THE

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