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Toyonaka, Japan

Fujishima H.,Osaka Prefecture University | Yoshioka Y.,Osaka Prefecture University | Kuroki T.,Osaka Prefecture University | Tanaka A.,Takao Iron Works Company | And 2 more authors.
Conference Record - IAS Annual Meeting (IEEE Industry Applications Society) | Year: 2010

A pilot-scale low emission boiler plant which consists of a multi-fuel boiler and a plasma-chemical hybrid NOx removal system was investigated. This plant can achieve carbon neutrality because the multi-fuel boiler uses waste vegetable oil as one of fuels. The plasma-chemical hybrid NOxremoval system has two processes; one is NO oxidation by ozone produced from plasma ozonizers, and the other is NO2removal using a Na2SO3 chemical scrubber. The operation tests of the plant were carried out for mixed oils (mixture of heavy oil and waste vegetable oil). Stable combustion was achieved for the mixed oil (20%∼50% vegetable oil). The flue gas properties, such as O2, CO2 and NO x in firing mixed oils, were nearly the same as those in firing heavy oil when the flue gas flow rate was 1000 Nmth/h on average. NO x concentrations at boiler outlet were 90∼95 ppm. Furthermore, it is confirmed that during a 300 min continuous operation in firing 20% mixed oil NOx removal efficiency was attained more than 90%, equivalent to less than 10 ppm at scrubber outlet when the flue gas flow rate was 870 Nm th/h. In addition, the effect of replacing heavy oil by waste vegetable oil on CO2 reduction was estimated. © 2010 IEEE. Source


Okubo M.,Osaka Prefecture University | Fujishima H.,Osaka Prefecture University | Yamato Y.,Osaka Prefecture University | Kuroki T.,Osaka Prefecture University | And 2 more authors.
Journal of Physics: Conference Series | Year: 2013

A pilot-scale low-emission boiler system consisting of a bio-fuel boiler and plasma-chemical hybrid NOx removal system is investigated. This system can achieve carbon neutrality because the bio-fuel boiler uses waste vegetable oil as one of the fuels. The plasma-chemical hybrid NOx removal system has two processes: NO oxidation by ozone produced from plasma ozonizers and NO2removal using a Na2SO3 chemical scrubber. Test demonstrations of the system are carried out for mixed oils (mixture of A-heavy oil and waste vegetable oil). Stable combustion is achieved for the mixed oil (20-50% waste vegetable oil). Properties of flue gas - e.g., O2, CO2and NOx - when firing mixed oils are nearly the same as those when firing heavy oil for an average flue gas flow rate of 1000 Nm3/h. NOx concentrations at the boiler outlet are 90-95 ppm. Furthermore, during a 300-min continuous operation when firing 20% mixed oil, NOx removal efficiency of more than 90% (less than 10 ppm NOx emission) is confirmed. In addition, the CO 2 reduction when heavy oil is replaced with waste vegetable oil is estimated. The system comparison is described between the plasma-chemical hybrid NOx removal and the conventional technology. © Published under licence by IOP Publishing Ltd. Source


Fujishima H.,Osaka Prefecture University | Kuroki T.,Osaka Prefecture University | Ito T.,Hitachi Zosen Corporation | Otsuka K.,Takao Iron Works Company | And 3 more authors.
IEEE Transactions on Industry Applications | Year: 2010

The process of removing NOx from the flue gas emitted from a smoke-tube boiler was investigated using an ozonizer, which is used for carrying out the indirect oxidation of NO, and a Na2SO3 chemical scrubber. The flow rate of the flue gas was in the range of 410-1480 N · m3/h, its temperature was in the range of 185 °C- 325 °C, and the concentration of NOx was approximately 40 ppm during the combustion of city gas. Operational and performance data were obtained from the experiments. The efficiency of the NOx removal process was clearly dependent on the oxidation reduction potential (ORP), and it increased with a decrease in the ORP of the scrubbing solution. To effectively remove the requisite amount of NOx, it is essential to maintain the ORP by controlling the injection rates of the Na2SO3 solution and maintaining an ORP of less than 0 mV and the rate of change in ORP to less than 0 mV/min. More than 4 kg/h of Na2SO3 must be added to the scrubber in order to sustain the aforementioned ORP condition of the scrubbing solution. The amount of NOx emitted from the flue gas was maintained as less than 4 ppm at a flue gas flow rate of 410 N · m3/h during a 300-min continuous system operation by maintaining an ORP of -30 mV and a pH of more than 7.8 for the scrubbing solution. © 2010 IEEE. Source


Fujishima H.,Osaka Prefecture University | Takekoshi K.,Osaka Prefecture University | Kuroki T.,Osaka Prefecture University | Tanaka A.,Takao Iron Works Company | And 2 more authors.
Applied Energy | Year: 2013

A super-clean boiler system comprising a multi-fuel boiler and a reactor for plasma-chemical hybrid NOx aftertreatment is developed, and its industrial applications are examined. The purpose of this research is to optimally reduce NOx emission and utilize waste bio-oil as a renewable energy source. First, NO oxidation using indirect plasma at elevated flue gas temperatures is investigated. It is clarified that more than 98% of NO is oxidized when the temperature of the flue gas is less than 130°C. Three types of waste bio-oils (waste vegetable oil, rice bran oil, and fish oil) are burned in the boiler as fuels with a rotary-type burner for CO2 reduction considering carbon neutrality. NOx in the flue gases of these bio-oils is effectively reduced by the indirect plasma-chemical hybrid treatment. Ultralow NOx emission less than 2ppm is achieved for 450min in the firing of city natural gas fuel. The boiler system can be successfully operated automatically according to unsteady steam demand and using an empirical equation for Na2SO3 supply rate, and can be used in industries as an ideal NOx control technology. © 2013 Elsevier Ltd. Source


Fujishima H.,Osaka Prefecture University | Tatsumi A.,Osaka Prefecture University | Tatsumi A.,Toyota Motor Corporation | Kuroki T.,Osaka Prefecture University | And 4 more authors.
IEEE Transactions on Industry Applications | Year: 2010

NOx removal from the flue gas of a smoke tube boiler using an ozonizer for NO oxidation and a Na2SO3 aqueous solution scrubber (diameter: 0.6 m; height: 3.7 m) was investigated. In this paper, in order to determine the correlation NOx removal performance, the height of the packing material layer in the scrubber was varied from 2.1 to 0 m. The performance tests were carried out using both a compressed natural gas (CNG) and a heavy oil. The flue gas flow rates were in the range of 4551440 Nm3h under CNG firing and 6751330 Nm3h under heavy oil firing, and the boiler NOx emission concentrations were approximately 40 and 100 ppm, respectively. A total packing height of 0.75 m resulted in NOx removal efficiencies of 70% and 60% for CNG and heavy oil, respectively. Moreover, the Na2SO3 consumption rate at 0.75 m was 10%20% less than that at 1.2 m, although the NOx removal efficiency was nearly the same. The correlation between the NOx removal performance and the gas retention time in the scrubber was obtained, providing the design information of the scrubber for industrial applications. © 2010 IEEE. Source

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