報告書番号

M13006

タイトル（和文）

石炭ガス化スラグの海域環境改善資材への活用に向けた調査 －深掘り跡埋め戻し資材としての評価－

タイトル（英文）

Consideration on use of IGCC slag as materials to improve marine environment - Evaluation as backfill material for depression on the seafloor -

概要 （図表や脚注は「報告書全文」に掲載しております）

石炭ガス化複合発電から排出される石炭ガス化スラグは､非晶質で有害成分を溶出せず､砂代替等として工事用資材に利用できると知られている｡一方､日本では､水辺環境や水産資源を守るため､覆砂､深掘り跡の埋め戻し等､砂を用いた様々な海域環境改善が進められており、石炭ガス化スラグの新たな有効利用先となる可能性がある。当該砂資材の需要や基準を調査し､石炭ガス化スラグの適合性を検討した｡深掘り跡は､海底の工事用土砂採取跡で青潮発生の一因とされ､既に埋め戻しが進んでいるが、特に大量の砂資材が必要であり、現在の資材量では東京湾だけでも全体修復に数十年かかる見込みで､リサイクル材活用の必要性が指摘されている｡当該用途砂資材の基準については、｢浚渫土砂の海洋投入処分｣基準が参考になると考えられ、①物理的,②化学的,③生化学的特性の3側面から評価する必要があるが、石炭ガス化スラグの場合、①物理的、③生化学的特性については海水を濁らせる微粒分や有害植物プランクトン含まないため、事実上②化学的特性の検証が重要と考えられる。そこで当該指針に基づき、当研究所の石炭ガス化スラグの溶出試験を行い､ほぼ全ての項目が基準値以下であることと確認した｡但し、具体的な基準は地域により異なる可能性があるため､排出事業者が実際の排出スラグを元に､工事施工海域所轄の担当機関に基準と適合性を確認する必要がある｡

概要 （英文）

IGCC system discharges coal ash as glassy amorphous IGCC slag particles quenched in water bath. The IGCC slag can be used for construction materials as substitute for natural sand, because slag doesn't emit any toxic elements. In Japan, it is regarded as important issue to maintain and to recover marine environment. Various approaches are under way, for example laying sand on the sea sediments or backfilling numbers of huge depressions on seafloor. It is significant to gather information on marine environmental recovery act and on necessary materials. This report is to describe status quo of marine environmental recovery act and to describe demand and standard of necessary materials for the act. In Japan the blue tide is regarded as serious pollution that damages fisheries seriously. One of the main causes of blue tide is regarded as existence of huge depressions on seafloor. Therefore backfill project for these depressions has started about 10 years ago using dredged sand. But lack of sand or appropriate substitutes prevent this backfill project and it is considered it takes quite a long time around 50 years. Ministry of Land, Infrastructure, Transport and Tourism (MLIT) and others recognize necessity of introduction of other materials, including recycled materials. It is difficult to define the standard of materials for marine environment recovery act, but MLIT report states that the standard for open sea dumping of dredged sand can be a reference. In this standard, dredged sand is evaluated from 3 aspects, namely physical properties, chemical properties, biological properties. IGCC slag doesn't contain any muddy fine particle, which is concerned to be a source of turbidity of sea water. And IGCC slag doesn't contain any germination species of harmful phytoplankton, which is concerned to be harmful for fisheries. Therefore it is considered that chemical properties are actual standard for IGCC slag. In this report, leaching examinations for 5 kinds of IGCC slag collected in 3TPD coal gasifier of CRIEPI was executed. As a result, it was proved leaching characteristics of all the examined items, 35 items among 39, passed the standard and any elements were not detected at all in the experiments. But we have to recognize that it is required for IGCC operating company to examine the applicability of their own IGCC slag and to explain it to responsible authorities of that field, because there may exist a local standard.

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