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RISS 인기검색어
- 검색키워드
- 저자 : Kunio Yoshikawa (검색결과 13 건)
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DISTRIBUTED GASIFICATION AND POWER GENERATION FROM SOLID FUELS
Kunio YOSHIKAWA 한국열환경공학회 2002 열환경공학 Vol.1 No.2
An innovative small-scale gasification system for solid fuels such as wastes and biomass is proposed which is known as STAR-MEET system. In this system, a fixed-bed pyrolyzer combined with a high temperature reformer using high temperature steam/air mixture is employed. From the experimental results using rubber chips as a fuel, it has been demonstrated that injection of high temperature steam/air mixture into the pyrolysis gas effectively decomposes tar and soot components in the pyrolysis gas into CO and H 2' and almost dust and tar free clean reformed gas can be generated. The STAR-MEET system requires high temperature steam/air generator, and a 900C class metallic type compact heat exchanger has been successfully developed. This gasification system generates low BTU gas from solid fuels. Thus power generation experiments using a dual fueled(light oil gas and low BTU gas) small diesel engine were done using a simulated low BTU gas produced from natural gas diluted with nitrogen. Compared with light oil only driven, dual fueled engine shows similar thermal efficiency with significantly low NOx emission. Finally, power generation experiments using a complete STAR-MEET plant has been successfully done. These results demonstrates small-scale gasification and power generation system using solid fuels is quite feasible.
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System development and analysis for producing high quality gas and activated sludge char
전영남,김성천,Kunio Yoshikawa 대한기계학회 2012 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.26 No.1
For energy and resource utilization of dried sewage sludge, an integrated system with in-line connection of pyrolysis gasifier, plasma reformer, and fixed bed adsorber was developed. The plasma reformer was set to improve producer gas yield by destructing tar released from the pyrolysis gasifier. The fixed bed adsorber filled with the sludge char produced from the pyrolysis gasifier was installed for adsorption of un-treated tar. The pyrolysis gasifier produced sludge char, tar and gas. The sludge char showed 98.1 m2/g of specific surface area and 63.49 Å of mean pore size, which had a good distribution of micropore and mesopore with superior adsorption rate of light PAH tar. The concentrations of gravimetric tar and total light tar were 26.3 g/Nm3 and 10.9 g/Nm3, respectively. The analyzed light tar was in the order of benzene, naphthalene, benzonitrile, benzeneacetonitrile, anthracene and pyrene. Produced gas was composed of hydrogen,carbon monoxide, methane, and carbon dioxide. The plasma reformer displayed 83.2% of removal efficiency with 4.4 g/Nm3 of gravimetric tar at the outlet due to tar cracking and steam reforming reaction. The total amount of light tar was 1.3 g/Nm3. Among the reforming gas, the concentration of hydrogen, carbon monoxide, and methane was increased. Gravimetric tar at the outlet of the adsorber was 0.5g/Nm3, which was 88.6% of removal efficiency. The total amount of light tar was 0.39 g/Nm3. Gas analysis results at the exit showed 50.5% H2, 21.9% CO, 10.5% CH4, 7.7% CO2 and 0.1% C2H2 with a higher heating value of 13,482 kJ/Nm3. Therefore, sewage sludge can be converted into energy and resource by pyrolysis and gasification since the producer gas and sludge char could be utilized in a heat engine and adsorption tower for tar removal, respectively.
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전영남,Dae Won Ji,Kunio Yoshikawa 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.1
A study on pyrolysis, steam gasification, and carbonization-activation was conducted to produce energy and resource from waste sewage sludge. Carbonization-activation is a sequential process of pyrolysis and steam gasification. The experiment was conducted with a batch-type fixed bed reactor. A comparative analysis on the formation characteristics of products, such as gas, tar, and char, was conducted to evaluate the three cases. For sludge char, carbonization-activation showed the largest amount of porosity in the char, and its specific surface area was 80.28 m2/g with an average pore diameter of 6.229 nm. The best adsorption ability of benzene, a light tar, was 175 mg/g. For the producer gas, steam gasification obtained the largest amount of 20.1 L. Similarly, carbonization-activation showed a large value of 16.6 L. Hydrogen and carbon monoxide concentrations were higher in the producer gas due to steam reforming compared with carbonization-activation. Energy yields were 209 kJ and 226 kJ for steam gasification and carbonization-activation, respectively. The amount of tar formation did not show a significant difference, but the largest one was found in steam gasification. The gravimetric tar amount for steam gasification was 23.5 g/Nm3. However, the selected light tar displayed the lowest concentration for the carbonization- activation. Such concentrations were 2.79 g/Nm3, 0.75 g/Nm3, 0.14 g/Nm3, and 0.14 g/Nm3 for benzene, naphthalene, anthracene, and pyrene, respectively. Therefore, carbonization-activation was found to be the most effective process for producing high quality sludge char and producer gas for utilizing waste sludge into renewable energy and resources.
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Characteristics of the product from steam activation of sewage sludge
전영남,Mun Sup Lim,Kunio Yoshikawa 한국공업화학회 2012 Journal of Industrial and Engineering Chemistry Vol.18 No.2
Steam activation of a dried sewage sludge was studied to produce hydrogen rich gas and sludge char for converting to energy and resources. A batch-type wire mesh reactor was used to study the characteristics of the steam activation. The characteristics of activation product (i.e., producer gas, gravimetric tar, light tar, and sludge char) were identified. With the increase in the steam feed rate, the sludge char decreased but the producer gas increased,having higher gas heating value. And tar generation slightly increased when a small amount of steam was fed, but when the steam feed rate significantly increased, tar decreased because part of the tar was converted into light gas. Hydrogen and carbon monoxide increased with the increase in the steam feed rate. And carbon dioxide, methane, ethylene, and ethane reached their maximum according to different production mechanisms up to decreasing the species. The gradually increase in the steam feed rate resulted in the creation of micropores, which developed to the maximum when the steam flow rate was 14 mL/g min. When excessive steam was supplied,however, micropores sank due to the resulting sintering phenomenon, and the adsorption capacity deteriorated. The sludge char had a mean pore size of 6.229 nm, which is the size of mesopores from which condensible tar (the cause of damage on the device) is properly adsorbed and removed.
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( Andile B. Maqhuzu ),( Kunio Yoshikawa ),( Fumitake Takahashi ) 한국폐기물자원순환학회(구 한국폐기물학회) 2016 한국폐기물자원순환학회 춘계학술발표논문집 Vol.2016 No.-
The quality of Municipal Solid Waste (MSW) management remains at a very low level in Zimbabwe. The challenges posed by inadequate and inappropriate tools for waste disposal are evident as Zimbabwe’s history is clouded by a string of fairly recent cholera and typhoid outbreaks. The urban areas are teeming with illegally dumped litter as cash-strapped local authorities are unable to collect the waste. An alternative strategy to prevent the problems associated with poor MSW disposal practices is needed. Waste management based on social, economic, and environmental conditions is necessary for the environment-friendly development of Zimbabwe. Electric power supply is also an important issue from the viewpoints of the economic growth and environmental protection. In Zimbabwe, where shortages in domestic coal production adversely affect electricity supply, a waste-to-energy technology can be a promising solution for waste related problems. The hydrothermal conversion of municipal solid wastes into green products has received much attention in recent years. The partial substitution of coal by hydrothermally treated MSW has been tested extensively and the optimum blend levels are well known. However, limited studies have looked at the application of this technology for power generation in developing countries at a national level. In Zimbabwe, where MSW collection and disposal is less developed, the feasibility of hydrothermal technology largely depends on the quantities and quality of waste that can be converted amongst other factors be they social or economic. The aim of this study is therefore to determine the potential maximum amount of collectable MSW that can be converted for co-burning with coal if the technology is implemented. A desk research approach was used to quantify and characterize Zimbabwe’s MSW. The qualitative analysis and quantification of the coal-alternative fuel produced by hydrothermal conversion of Zimbabwe MSW was predicted using a model. The model was developed using extensive experimental data in published works covering hydrothermal conversion, Zimbabwe MSW characteristics, typical heating values, ultimate and proximate analysis of MSW components. Coal consumption at Zimbabwe’s coal-fired power stations was estimated based on reported plant capacities and Zimbabwe coal chemistry. Results from the model were compared with other investigations to establish confidence in the approach. The preliminary findings indicate that the quantities of MSW and theoretical yield of coal-alternate fuel justify the possibility of utilizing hydrothermal technology. When all of the coal-alternate fuel produced from MSW is utilized in coal-fired power plants with dependable operation capacity, 14.8% of the coal will be substituted, which is less than maximum acceptable substitution ratio (20%). However, further investigations such as cost analysis, or social feasibility analysis still need to be conducted to provide a conclusive answer to the question on the applicability of this technology in Zimbabwe.
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Effect of waste-to-energy via hydrothermal treatment on greenhouse gas emissions in Zimbabwe
( Andile B. Maqhuzu ),( Kunio Yoshikawa ),( Fumitake Takahashi ) 한국폐기물자원순환학회(구 한국폐기물학회) 2017 한국폐기물자원순환학회 심포지움 Vol.2017 No.1
Landfilling remains a significant source of greenhouse gas (GHG) emissions and a major contributor to total anthropogenic methane emissions leading to global warming. For developing nations, landfilling is by far the lowest cost disposal method and it is likely to remain a favourable option as harsh economic conditions will likely impede the adoption of more environmentally-friendly technologies. Hydrothermal treatment (HTT), a relatively cheap waste-to- energy option, has the potential to solve a growing share of problems caused by the unsanitary disposal of municipal waste (MSW) in Zimbabwe. Groundwater contamination due to unconfined leachate flow and GHG emissions from landfills can be reduced if MSW is redirected to HTT plants. The thermochemical process involves the charring of carbohydrate feedstock at a relatively low-temperature atmosphere (180°C-350°C) and high autogenous pressure (up to 2.4 MPa) using steam to produce hydrochar or biocoal which resembles lignite-coal in its composition and properties. There is, however, uncertainty in the quantity of waste generated and subsequent emissions. This is largely caused by the lack of reliable MSW data collection systems at a local and national level in developing nations. The aim of this study is therefore to determine the amount of landfilled MSW, its energy potential and total expected GHG emissions using risk analysis tools to account for this uncertainty. Palisade’s @Risk tool, an Excel spreadsheet plug-in, was used to quantify and characterize Zimbabwe’s MSW using reported values of Zimbabwe MSW characteristics, typical heating values, ultimate and proximate analysis of MSW components. Estimates of landfill gas (LFG) emissions were based on the Intergovernmental Panel on Climate Change (IPCC) methodology of a Zero-Order Model which assumes fairly steady LFG emissions with time. Waste age presumably has no effect on LFG production using this model. Instead of using static values for all parameters concerned, stochastic values and probability distributions were used supported by 100 000 Monte Carlo simulations. 2016 was chosen as the year for our analysis to determine the effect of HTT on GHG emissions. Simulation results, at a 90% confidence interval, indicate that 556-1452 Gg of MSW was generated by Zimbabwe’s urban population in 2016. This estimation also suggests that 400-1237 Ggwas collected and openly dumped in unsanitary landfills representing about 5.91-18.5 PJ of energy that was merely wasted by not extracting its value. The mean in total GHG emissions expected from this landfilled MSW as shown in Fig. 1 is about 869 Gg CO<sub>2e</sub> using the IPCC methodology. Assuming that up to 100% of this waste can be diverted to hydrothermal treatment for value addition, total GHG emissions can be reduced to a range of about 33-1151 Gg CO<sub>2e</sub> (at 90% confidence level) and a mean of about 435 Gg CO<sub>2e</sub>
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