Research Repository :: Browsing by Author "Naruse, Ichiro"

Browsing by Author "Naruse, Ichiro"

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Comparative Study of Lead and Cadmium Compounds Capture by Sorbents
(2002-04) Yao, Hong; Saito, Noboru; Mkilaha, Iddi; Naruse, Ichiro
Trace metal compounds, which are emitted from combustion systems such as waste incinerators, coal combustors, and so forth, enrich in fine particulates, usually formed during various stages of combustion. Owing to the difficulties of capturing fine particulates by conventional particulate dust collection systems, these are exhausted in the atmosphere. Fundamentals of the emission and control of trace metal compounds of lead and cadmium were studied at relatively low temperature (1073-1273 K), using a thermobalance. In order to capture these trace metal compounds, seven types of sorbent, namely alumina, silica, kaolin, limestone, scallop, zeolite and apatite, were used. As a result, the natural aluminosilicate materials like kaolin and zeolite were found to be effective in capturing lead and cadmium chemically. Although the presence of HCl decreases capture efficiencies, the products didn't react with HCl. The types of kaolin had a little influence on the capture efficiency and processes in general. On the other hand, the calcium-based sorbents like limestone, scallop and apatite, could capture both the trace metals and chlorine. On the presence of HCl, the capture efficiencies of these sorbents decreased sharply. Both alumina and silica have low ability to capture trace metal compounds. Moreover, in reducing atmosphere, all sorbents showed low capture abilities since the products were reduced.
Contribution of Volatile Interactions during Co-gasification of Biomass with Coal
(Life science Global, 2013) Kihedu, Joseph H.; Yoshiie, Ryo; Nunome, Yoko; Naruse, Ichiro
Thermo-gravimetric behavior during steam co-gasification of Japanese cedar and coal was investigated. The difference between co-gasification behavior and the average gasification behavior of cedar and coal indicates two synergetic peaks. The first peak occurred between 300 °C and 550 °C while the second peak was observed above 800 °C. The first peak coincides with volatile release and therefore associated with volatile interactions while the second peak is linked with catalytic effect of alkali and alkaline earth metal (AAEM). Acid washed cellulose and Na rich lignin chemicals were used as artificial biomass components. In reference to Japanese cedar, mixture of cellulose and lignin i.e. simulated biomass, was also investigated. Co-gasification of cellulose with coal and co-gasification of lignin with coal, demonstrates contribution of volatile interactions and AAEM catalysis respectively. Morphology of partially gasified blends, shows hastened pore development and physical cracking on coal particles. Brunauer−Emmett−Teller (BET) surface area of the charred blend was lower than the average surface area for charred biomass and coal.
Conversion Synergies during Steam Co-Gasification of Ligno-Cellulosic Simulated Biomass with Coal
(Scientific Research, 2012-12) Kihedu, Joseph H.; Yoshiie, Ryo; Nunome, Yoko; Ueki, Yasuaki; Naruse, Ichiro
Lignin and cellulose chemicals were used as artificial biomass components to make-up a simulated biomass. Alkali and Alkaline Earth Metal (AAEM) as well as volatile matter contents in these chemicals were much different from each other. Co-gasification of coal with simulated biomass shows improved conversion characteristics in comparison to the average calculated from separate conversion of coal and simulated biomass. Two conversion synergetic peaks were observed whereby the first peak occurred around 400℃ while the second one occurred above 800℃. Although co-gasification of coal with lignin that has high AAEM content also shows two synergy peaks, the one at higher temperature is dominant. Co-gasification of coal with cellulose shows only a single synergy peak around 400℃ indicating that synergy at low temperature is related with interaction of volatiles. Investigation of morphology changes during gasification of lignin and coal, suggests that their low reactivity is associated with their solid shape maintained even at high temperature.
Counter-flow air gasification of woody biomass pellets in the auto-thermal packed bed reactor
(Sciencedirect, 2014-01) Kihedu, Joseph H.; Yoshiie, Ryo; Nunome, Yoko; Ueki, Yasuaki; Naruse, Ichiro
Counter-flow packed bed gasification was carried out featuring a combination of downdraft and updraft operation modes. A column reactor of inside diameter 102 mm and 1000 mm height was used. Downdraft and updraft air supply were varied while the total air supply was maintained constant. Counter-flow gasification with downdraft air supply at 12 L/min and updraft air at 4 L/min offered optimal conditions, producing syngas with 4.28 MJ/m3 N LHV and 5.84 g/m3 N tar content. Under similar operating conditions, cold gas efficiency was about 77% while carbon conversion reached 88%. Increasing the updraft air flow resulted in reduced tar generation and increased carbon conversion, however, the syngas LHV and cold gas efficiency were affected adversely.
Formation Characteristics of Fine Particulates with Na Compounds during Coal Combustion
(2003-10) Takuwa, Tsuyoshi; Mkilaha, Iddi; Naruse, Ichiro
Some metal compounds in coal vaporize and form fumes during the combustion. The fumes are usually exhausted through the flue gas. For coal-fired combined power generation systems such as pressurized fluidized bed combustion (PFBC), hot metallic vapors may contact with the surfaces of gas-turbine blades. Since this contact of the hot vapors with the surface has a corrosive effect, it is necessary to control the formation of those fumes, which contain alkali metal compounds. In this paper, the evolution behavior of alkali metal compounds, especially sodium compounds, has been studied, using an electrically heated drop tube furnace with a low-pressure impactor. The main objective in this study is to elucidate the conditions and the possible mechanisms to form alkali metal compounds in particulate matter during combustion. Two types of coal with different sodium contents were tested, where the coal conversion characteristics were established. Furthermore, the evolution and inclusion of sodium compounds into the sub-micron particles were studied in relation to the particle size distribution and sodium fraction distribution in the collected particulates. The study proved that the evolution and inclusion of sodium on sub-micron particles depended on the functions of the coal type. The reaction-controlled mechanism and heterogeneous condensation via chemical reactions during the combustion much more influenced the inclusion of sodium in sub-micron particles. At the coarse particles of above about 0.5 μm, the reaction that formed the particles was mainly via gas film diffusion surrounding the particle.
Fundamentals on Vaporization Behavior of Trace Metal Compounds at Different Atmospheres and Temperatures.
(2001-12) Yao, Hong; Mkilaha, Iddi; Naruse, Ichiro
Trace metals are usually inevitably contained in wastes, coals and so forth. When the wastes and/or coals are burnt, pollutants like NOx, SOx, soot, particulates, dioxins and heavy metal compounds are emitted from the furnaces. Some of the heavy trace metal compounds condense on the particle surface and/or form fine particulates during the combustion/incineration processes. Owing to the difficulties in capturing those fine particulates by means of conventional dust collection systems, those particulates tend to be exhausted into the atmosphere. In this study, fundamental behavior of the vaporization of Pb, Cd and Cr compounds was studied at relatively low temperature. In this experiment the effects of temperature and reaction atmosphere on the vaporization behavior of Pb, Cd and Cr compounds were studied using a thermobalance. The chemical thermoequilibrium calculation for each compound was also carried out in order to validate the experimental results obtained. As a result, the vaporization behavior of the metal compounds appears dependent on their respective melting points. Most of chlorides were easily vaporized at relatively low temperatures. This suggests that the presence of HCl enhances the vaporization of metal compounds, while co-existence of SO2 shows inhibition of the vaporization tendencies of Pb and Cd compounds. All of the Cd compounds vaporized in the reducing conditions. The results of chemical thermoequilibrium calculation agreed closely with the experimental results obtained.
Gasification characteristics of woody biomass in the packed bed reactor
(Sciencedirect, 2011) Ueki, Yasuaki; Torigoe, Takashi; Ono, Hirofumi; Yoshiie, Ryo; Kihedu, Joseph H.; Naruse, Ichiro
Gasification technology is recognized as one of the possibilities for utilizing biomass effectively. This study focused on woody biomass gasification fundamentals, using a bench-scale packed-bed reactor. In this experiment, pellets of black pine were gasified, using air as the oxidizing agent. Gasification tests were carried out under both updraft and downdraft conditions. Temperature distributions and compositions of syngas inside the gasifier were continuously monitored during gasification experiments at several ports on the wall of the reactor. The syngas at the exit of the gasifier was also sampled to estimate the amount of tar. Lower heating values of the syngas under updraft and downdraft conditions were 4.8 and 3.8 MJ/m3N, respectively. It was easier to control the height of the packed bed under the downdraft condition than under the updraft condition. Under the updraft condition, a bridging phenomenon occurred. Tar generation under the downdraft condition was lower than that under the updraft condition. This is because tar passes through a partial combustion zone or higher temperature zone in the downdraft gasifier.
Influence of Gas Type and Injection System on Simultanous Reduction of Soot and NOx in IDI Diesel Engine.
(1995-09) Mkilaha, Iddi; Kawai, Daizaburo; Inoue, Mitsunori; Naruse, Ichiro; Ohtake, Kazutomo
Modification has been made to one of the prechambers of a 4-cylinder. IDI diesel engine used to study the combustion process, for the purpose of reducing emissions. With the provisions for optical assessment o the combustion process in the prechamber, the effect of high-pressure gas injection into the prechamber during injection has been carried out. Results of this work indicate that high-pressure gas injection during combustion can affect simultaneous soot and NOx reduction with a reasonably low amount of emission of other diesel engine pollutants. An optimum chamber type is suggested based on analysis of the effect of air, argon and nitrogen injection.
Mechanisms of fine particulates formation with alkali metal compounds during coal combustion
(2006-02) Takuwa, Tsuyoshi; Mkilaha, Iddi; Naruse, Ichiro
Two types of coals with different sodium (Na) and potassium (K) concentrations were burned in an electrically heated drop tube furnace, to study the formation of particulates in association to alkali metal compounds from the coals. The particulates formed from these coals during combustion were separated by a low pressure impactor (LPI). The particulates collected in each stage of the LPI were analyzed, using an atomic adsorption spectrometer (AAS). The results obtained show that ash particles have bimodal particle size distribution for both coal types. This tendency could be due to the difference of the inherent minerals in raw coals. It was further observed that Na and K were enriched in the fine particulates for both types of coal. There was a dependence of the Na enrichment on the fine particles on concentration of excluded mineral in the raw coals. This work, therefore, showed that the appearance of alkali metal in the ash particles related to the nature of Na and K concentrations in raw coals.
Performance indicators for air and air–steam auto-thermal updraft gasification of biomass in packed bed reactor
(Sciencedirect, 2015-08-08) Kihedu, Joseph H.; Yoshiie, Ryo; Naruse, Ichiro
Auto-thermal updraft gasification of biomass pellets in a packed bed reactor was conducted by using air and air–steam mixture. Air–steam gasification produced syngas with slightly improved lower heating value of 4.5 MJ/mN3 in comparison to 4.4 MJ/mN3 produced during air gasification. The corresponding tar generation for air gasification and air–steam gasification was 21.2 g/mN3 and 26.2 g/mN3, respectively. Cold gas efficiency for air gasification and air–steam gasification was realized to be 91% and 91.4%, respectively. Carbon conversion during air–steam gasification reached about 91.5% while carbon conversion during air gasification was limited to 84.3%.
Reaction Characteristic of Woody Biomass with CO2 and H2O
(J Stage, 2010) Naruse, Ichiro; Ueki, Yasuaki; Isayama, Tsutomu; Shinba, Takanori; Kihedu, Joseph H.; Yoshiie, Ryo
Objective in this study is to elucidate the fundamental gasification characteristics for carbonaceous resources. Effects of temperature and gaseous agents on the gasification characteristics of carbonaceous materials were experimentally and theoretically studied by the gasification of woody sawdust, using an electrically heated drop tube furnace. Results of the co-gasification of CO2 with H2O were compared by the gasi- fication by a single gaseous agent such as CO2 or H2O. As a result, H2 and CO concentrations increased with an increase of temperature. CO concentration under the co-gasification condition produced more than that under the single gasification condition. The H2 formation showed the opposite tendency to the CO formation during the co-gasification. This synergy effect was also elucidated theoretically by the simulation of reaction kinetics. The simulated temperature indicating the maximum synergy effect on CO formation agreed well with that obtained by the experiments.
Reduction of pollutants from diesel exhaust by high pressure gas injection
(1997-06) Kawai, Daizaburo; Mkilaha, Iddi; Osawa, Takuya; Naruse, Ichiro; Ohtake, Kazutomo
In order to reduce the pollutants from diesel exhaust, high-pressure gas was injected during combustion into a modified pre-chamber of an IDI diesel engine at a varied load and gas injection timing. The result shows that high-pressure gas injection can reduce the particulates and NOx simultaneously, with little influence on the engine performance. The combustion process in the pre-chamber was visualized by means of an ultra high-speed video system and image analysis of the pictures obtained. The results of the visualization show that by injecting gas, the flame is first quenched, followed by the reduction of NOx in the pre-chamber by hydrocarbon. Although high-pressure gas injection could have caused a substantial increase in HC as a result of temperature quenching, this seems to be controlled by the consumed portion of HC during the recycling of NOx. Chemical analysis of polycyclic aromatics compounds was carried out for the purpose of establishing its variations with gas injection. It was established that gas injection not only reduces PM by oxidation of solid carbon, but also the PAH component.
Screening of sorbents and capture of lead and cadmium compounds during sewage sludge combustion
(2004-04) Yao, Hong; Mkilaha, Iddi; Naruse, Ichiro
Current understanding has shown that aluminosilicate- and calcium-based sorbents could be applied to control trace metals emission from combustion and incineration processes. However, the use of industrial commercial sorbents is not always appropriate. The present study dwells on the use of natural and waste materials as sorbents to capture lead and cadmium compounds during combustion. The main task is to optimize the use of those materials by screening them, using a thermobalance. Then, the determined optimum sorbent was tested on an electrically heated drop tube furnace, burning sewage sludge at temperatures ranging from 1073 to 1223 K. The results showed that some of aluminosilicate-based sorbent were more effective than calcium-based sorbents. Kaolin was found to be a relatively effective sorbent for Pb and Cd capturing. The results further showed that the capture ability depended on chemical compositions and specific surface area of the sorbents. Presence of HCl caused a little decrease in the capture ability, using aluminosilicate-based sorbents, while significant effect on the capture processes was noted when calcium-based sorbents were used. Furthermore, when kaolin was added into the sewage sludge, kaolin was an appropriate sorbent to control lead and cadmium emissions. Temperature increase enhances the capture ability under our experimental conditions. Kaolin addition played a role for low leachability of the trace metals.
Simultaneous reduction of particulate matter and NOx in a diesel engine by compressed gas injection: Macroscopic study at residual load
(1997-02) Mkilaha, Iddi; Inoue, M; Kawai, Daizaburo; Naruse, Ichiro; Ohtake, Kazutomo
A modified pre-chamber of an indirect injection (IDI) diesel engine was used to elucidate the influence on emissions of compressed air injection into the pre-chamber during combustion. The test parameters were air injection timing and arrangements of gas injection. This paper presents the experimental results for two types of injection arrangements; I- and Y-type. The I-type is arranged such that the gas injection jet and fuel injection nozzle are in opposite directions, while the Y-type is such that it forms a ‘Y’ shape with the nozzle and the passageway. Results obtained reveal that the Y-type arrangement is superior in combustion characteristics and emissions reduction to the I-type. A remarkable reduction in both particulate matter (PM) and NOx is realized at air injection timings during 35° and 65° after top dead centre (ATDC). The reduction mechanism can be explained as due to the induced turbulence which improves mixing and heat transfer. The effect of the modifications on the performance of the engine was evaluated based on the fuel economy and efficiency. This evaluation has shown that the test cylinder approximates closely to the normal cylinder of the original engine
Sorbent control of trace metals in sewage sludge combustion and incineration
(2013-04) Naruse, Ichiro; Yao, Hong; Mkilaha, Iddi
Coal and wastes combustion have become an important issue not only in terms of energy generation but also environmental conservation. The need for alternative fuels and wastes management has made the two energy sources of importance. However, the utilization of the two is faced with problems of impurity trace metals in the fuel. These metals usually speciate during combustion or incineration leading to generation of fumes and subsequently particles. This paper reports on the study aimed at understanding the speciation of trace metals and their emission from combustion systems as particulates. Experiments carried out using a down-flow furnace and theoretical study carried out using lead, chromium and cadmium as basic metals had shown that their speciation and subsequent emission is controlled by both chemical composition and physical properties of the fuel. The physical and chemical and physical properties of the fuel and their respective compounds and the operating conditions of the incineration and combustion system control the enrichment of the particles with trace metals.
Thermodynamic analysis of the role of chlorine and sulfur environments during combustion and incineration processes
(2002-09) Mkilaha, Iddi; Yao, Hong; Naruse, Ichiro
In order to control the emission of trace metals from combustion and incineration systems, sorbents and filters are sometimes used. However, the effectiveness of these methods is greatly affected by the volatility of the metals and the way in which they speciate during combustion, and afterwards during condensation, and physical or chemical sorption. Although there has been a lot of research into the mechanisms by which trace metals speciate and subsequently appear in submicron particles, the details of these mechanisms are not yet thoroughly understood. In this study, a chemical equilibrium approach was used to qualitatively determine the speciation of lead, cadmium, and chromium in Cl and S environments. The reaction conditions of sorbents were also tested numerically in order to understand the reaction behavior of metals with sorbents. This article reports the influence of different concentrations of Cl and SO2 on Pb, Cd, and Cr speciation, as representatives of other trace elements. The partitioning behavior of metals during combustion was also examined for Cl and S. The results obtained indicate that most metals exist in the vapor phase, even at low temperatures, when chlorine is present. However, the addition of SO2 enhances the formation of the condensed phase, except at extremely high temperatures. This observation was not significant for Cd or Cr. The higher the concentration of Cl the higher the retention of trace metals in the vapor phase, even at low temperatures. Results from comparisons of the reactivities of mixed metals with Cl indicate that the presence of Fe limits the reactivity of most trace metals with Cl except at higher concentrations. In the presence of Fe, alkali metals are the first to react with Cl. If Fe is not present, most trace metals react with Cl, and the activity increases with higher concentrations. On the other hand, the partitioning characteristics of S show that its presence generally means that metals remain in the condensed phase. Sulfur is more reactive with alkali metals than with other trace metals.
Trace-metal speciation during sludge combustion and incineration
(2002-10) Mkilaha, Iddi; Yao, Hong; Naruse, Ichiro
Municipal waste combustion has been opted as a method for reducing the size of the volume, and consequently, for reducing the necessary requirement of areas for direct disposal. However, the emission of the conventional gaseous pollutants are not the only problem; traces of metal fumes emanate from the metallic compounds that are in the wastes. Efforts to control these metal fumes have not been so successful because of the complicated mechanisms of the metallic compounds during combustion. Failure of the conventional systems to trap the trace elements is due to their appearance with the submicron particles from the combustion and incineration systems. In this work, a thermochemical equilibrium approach is employed to study the combustion and gasification behavior of trace metals with a case of lead, cadmium, and chromium during the incineration of sewage sludge. In this work, sulfur and chlorine have been found to play a key role in the speciation of the trace metals. However, these elements are only active when oxygen is present. A test on alkali metals mixed with trace metals showed that at low concentrations of S and Cl, the alkali metals react first with these elements before other metals. Chlorine assists in retaining most of the trace metals in the vapor phase while sulfur keeps them in the condensed form. The presence of iron, as is the case with most sorbents, hinders the reaction of Cl with the metals, thus suppressing the formation of volatile compounds.

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