Demonstration Plant at Ichikawa	Inductively-Coupled r.f. Plasma Reactor (80mm(i.d.) × 400mm(height))

Countermeasure Technology for Chemical Compounds

Organic halogenated compounds are used widely in various industries and in our daily lives. However, some compounds are toxic and some may generate hazardous by-product such as dioxin if incinerated in the conventional way. Thus, proper treatment is required when these compounds enter in the waste stream. In order to prevent dioxin emissions from incineration facilities and to define proper criteria for safe incineration, NIRE is researching the mechanisms of hazardous by-product generation in combustion reactions.

Fig:Study of the reaction mechnism using the flat flame burner

[Thermal Energy and Combustion Engineering Department]

Some chemicals that enter the environSent are highly toxic and biorefractory. Such compounds easily accumulate and concentrate in living tissues. In order to protect our water and soil resources, as well as human and ecological health, it is important to remove toxic chemicals from wastewater and to clean up pollution. NIRE is studying an ecological wastewater treatment and environmental remediation that uses enzymes (e.g., tvrosinase, peroxides and laccase). Potentially hazard chemicals in wastewater are oxidized by enzymes and converted to substances that easily precipitate with a coagulant. The precipitates are later detoxified and degraded by anaerobic bacteria. To further the development of enzymatic remediation, NIRE is investigating the incorporation mechanism of hazardous chemicals into soil and sediment humus by enzymatic catalysis. NIRE is also studying mass production of powerful enzymes by genetic engineering.

[Hydrospheric Environmental Protection Department]

Many physical and chemical means for eliminating hazardous organic chemicals have been developed and examined. Some waste-water treatment techniques can be and effective at highly polluted and compact sites, but ineffective at less polluted and spacious sites. Bioremediation, or elimination of hazardous chemicals by living organisms, is considered to be the most effective means for less polluted and spacious sites. NIRE's bioremediation studies focus on the following topics:


• Determination of biodegradation activities and pathways of hazardous organic chemicals in polluted sites.
• Enrichment of the microorganisms and control of the microbial activity responsible for hazardous organic chemical degradation at low concentrations.
• Physiological and genetic characterization of such microorganisms.

[Hydrospheric Environmental Protection Department]

Technologies which use ozone (O₃) degrade biorefractoi are generally divided into two groups: partial oxidation, which uses ozonation as a pretreatment for biological treatment, and combined oxidation, which combines the use of ozone and other physico-chemical treatments. Partial oxidation by ozone is an effective pretreatment for bioremediation because the biodegradability (e. g. ratio of 5-day biological oxygen demand to total organic carbon BOD5/TOC) of most chemicals is enhanced by ozonation, due to the introduction of oxygen into their molecular structures. Combined oxidation uses active radicals such as hydroxyl radical (OH-) instead of ozone molecules and can improve the degradation of biorefractory chemicals. Degradation of nitrophenols and dyes are studied at NIRE to enhance biodegradability and decrease the potential for organic halide formation.

[Hydrospheric Environmental Protection Department]

Mitigation of NOx

The sulfur oxides (SOx) and nitrogen oxides (NOx) emitted by fossil-fuel combustion damage health and cause acid rain. Although control processes for SOx and NOx in large-scale combustors are in commercial use, NOx-control technologies for small-scale combustors, particularly diesel engines, are still under development. NIRE has been investigating a de-NOx catalyst that can be applied to diesel exhaust systems. NIRE research chemists have developed a new catalyst that can effectively reduce NOx using alcohol as a reductant, instead of the more toxic ammonia. This technology is expected to contribute to the spread of highly efficient heat and power cogeneration systems.

[Atmospheric Environmental Protection Department]

Atmospheric constituents such as chlorofluorocarbons (CFCs) and CFC substitutes, greenhouse gases and nitrogen and sulfur compounds undergo photochemical reactions either directly or indirectly in the presence of sunlight. In an unbalanced system, these can build up in the atmosphere rather than eventually being removed. NIRE is especially concerned with heterogeneous processes in which particulate matter and aerosols play a role. We have found that a mixture of titanium dioxide (TiO₂) and activated carbon can remove nitrogen and sulfur oxides to the levels of environmental standards (about 0.05 parts per million, or ppm). As this photocatalyst is activated by sunlight and regenerated by rainfall, it can purify ambient air naturally without additional energy use. Tests of these air-purifying materials are being conducted at the sides of roads with heavy traffic. Some local governments have begun considering their use.

[Global Warming Control Department]

Decomposition of Chlorofluorocarbons

NIRE is actively developing strategies and new technology to mitigate stratospheric ozone depletion. One option is the development and diffusion of technology for the decomposition of chlorofluoro carbons (CFCs) and halons presently used in many industrial applications. It had been previously considered that CFCs and halons had previously were mostly inactive due to their thermal and chemical stability.

NIRE has pioneered a revolutionary new method to decompose these environmentally unfriendly compounds using plasma torches. When a radio-frequency current of 2 to 5 MHz is applied to a coil would 3 or 4 times around a specially designed tube ca. 6 cm in diameter and 20cm in hight, a plasma flame reaching temperature higher than 10,000^oC can be ignited inside the tube where gaseous and stable compounds are instantaneously activated in the plasma. In 1988, NIRE successfully demonstrated this phenomenon as a means to decompose CFCs. Presently, a demonstration plant with a mounted a 100kW plasma torch is decomposing waste CFCs in Chiba prefecture. The capacity of this plant exceeds 50 kg/h with an outstanding efficiency of more than 99.99%, and emissions to air and water are far below the limits set by government environmental standard.

[Atmospheric Environmental Protection Department]

Mitigation of Greenhouse Gases

CO₂ is the most serious greenhouse gas causing global warming. Unless effective control are implemented, atmospheric CO₂ leaves are expected to continue to rise. Chemical utilization of CO₂ released from typical stationary sources such as power plants, steel factories, and chemical plants would curb atmospheric CO₂ emissions. Furthermore, if various useful chemicals could be produced from CO₂, a new chemical industry using CO₂ as carbon source could established. Among various CO₂-utilization technologies, NIRE is study catalytic hydrogenation of CO₂ to produce fuels and commodity chemicals, and developing new chemical reactions using CO₂.

[Global Warming Control Department]

Our continuing consumption of fossil fuels produces 20 billion tons per year of CO₂ gas. About half of this CO₂ dissolves into the ocean or is incorporated into biomass.

The ocean has an enormous capacity for CO₂ absorption. Several options of technologies that can sequester, and thus dispose of, CO₂ in the ocean.

NIRE has developed the Gas Lift Advanced Dissolution (GLAD) system for sequesting CO₂ economically and without additional energy consumption. In the GLAD system, CO₂ gas is injected to a shallow depth in the ocean, where it dissolves into sea-water and is transported to the deep ocean through a reverse J-shaped gravity pipe.

[Mining and Geotechnology Department]