Search

The social and economic losses caused by viruses such as SARS-CoV, MERS-CoV, and SARS-CoV-2 has been serious In this study, the size of airborne droplet nuclei particles and the number of virions generated by speaking or coughing were analyzed Particle collection efficiencies of E11 and H13 grade air filters used in commercial air purifiers were evaluated for different particle sizes and the possibility of removing the airborne droplet nuclei particles by air purifiers was studied In addition, the reduction of SARS-CoV-2 virion concentration and dose by using air purifiers was theoretically investigated for elementary school classrooms When an infected student continuously emits virions with a rate of 6 0x10(5) virions/h in a 165 m(3)-sized classroom, the virion concentration and dose was estimated to be reduced by more than 60% by using an air purifier of clean air delivery rate (CADR) 780 m(3)/hr and by more than 70% by using two air purifiers (that is, CADR 1560 m(3)/h) compared to when not in use of the air purifier However, to prevent the spread of infection by the air stream generated by the air purifier, it is necessary to operate an instruction for using the air purifier such as facing the air outlet toward the ceiling and installing at least 50 cm away from occupants

Gasification characteristics and gas produced from a sewage sludge char were analyzed by using a thermobalance reactor, which is used for a reaction kinetic analysis by measuring weight change of materials at a desired temperature. Gasification reaction rate increased with increasing temperature and steam partial pressure due to the promotion of gasification reaction. Three models of gas-solid reaction were applied to the reaction kinetics analysis and modified volumetric reaction model was an appropriated model for the steam gasification of the sewage sludge char. Apparent activation energy and pre-exponential factors were evaluated as 155.5 kJ/mol and , respectively. The order of reaction on steam partial pressure was 0.68. Gas analysis was performed at and hydrogen concentration was highest in the gas concentrations, which increased with increasing the steam partial pressure. Hydrogen concentration increased the most and hydrogen concentration in the produced gas was 2-4 times higher than that of carbon monoxide due to the gasification and water gas shift reaction.

Oxy gasification was performed for the production of high quality syngas from the waste. was used as reactant with for gasification and greenhouse gas reduction. Therefore, gasification was performed at high temperature of . RPF was gasified in the thermobalance and 0.5 ton/day pilot plant gasifier. Weight variation with temperature and CO production by Boudouard reaction were studied for gasification of RPF in thermobalance reactor. Syngas of high concentration was produced from oxy gasification in 0.5 ton/day pilot system, which showed appropriate /CO ratio for the production of transport fuel and chemical products.

Steam gasification of sawdust char was performed in a thermobalance reactor at high temperature. Gasification temperature was changed from to and steam partial pressure was 0.3, 0.5 and 0.7 atm. Three models of gas-solid reaction were applied to the reaction kinetics analysis and modified volumetric model was an appropriate model. Reaction control regime and diffusion control regime were distinct depending on the temperature. Apparent activation energy and pre-exponential factors for both of the regimes were evaluated and the effects of steam partial pressure were examined. concentration in the produced gas was two times higher than that of CO due to the gasification accompanying by the water gas shift reaction.

Destruction of HFC-134a from ELV (End of Life Vehicle) were determined in a gasification-melting demonstration system of municipal solid waste (100ton/day). The injection system has been developed for the uniform injection of HFC-134a to the gasification-melting system. The destruction characteristics of HFC-134a and analysis of exhaust gases have been performed. The destruction efficiency was 99.995% for HFC-134a feeding of 3 kg/hr and the exhaust gases such as CO, SOx, NOx, HCl and HF satisfied the environmental standards.

Operating conditions for low-temperature pyrolysis and steam reforming of plastics over a ruthenium catalyst were investigated. In the range studied, the highest gas and lowest coke fractions for polystyrene (PS) with a 60 g h−1 scale, continuous-feed, two-stage gasifier were obtained with a pyrolyzer temperature of 673 K, steam reforming temperature of 903 K, and weight hourly space velocity (WHSV) of 0.10 g-sample g-catalyst−1 h−1. These operating conditions are consistent with optimum conditions reported previously for polypropylene. Our results indicate that at around 903 K, the activity of the ruthenium catalyst was high enough to minimize the difference between the rates of the steam reforming reactions of the pyrolysates from polystyrene and polypropylene. The proposed system thus has the flexibility to compensate for differences in chemical structures of municipal waste plastics. In addition, the steam reforming temperature was about 200 K lower than the temperature used in a conventional Ni-catalyzed process for the production of hydrogen. Low-temperature steam reforming allows for lower thermal input to the steam reformer, which results in an increase in thermal efficiency in the proposed process employing a Ru catalyst. Because low-temperature steam reforming can be also expected to reduce thermal degradation rates of the catalyst, the pyrolysis-steam reforming process with a Ru catalyst has the potential for use in small-scale production of hydrogen-rich gas from waste plastics that can be used for power generation.

We studied fuel gas production by means of pyrolysis and steam reforming of waste plastics for applications in solid oxide fuel cells. More specifically, we evaluated the effects of pyrolytic gasification temperature, catalyst content, steam reforming temperature, and weight hourly space velocity for a Ru catalyst used in a 60 g h− 1-scale continuous experimental apparatus, which consisted of a tank reactor for pyrolysis and a packed-bed catalytic reactor for steam reforming. Polypropylene (PP) pellets were used as a model waste plastic. Ru/γ-Al2O3 catalysts with two different Ru contents were investigated. To suppress residue formation, the optimum operating temperature of the pyrolyzer was 673 K. To ensure suppressed coke formation, sufficient carbon conversion to gaseous products, and minimized heat loss from the reactor, the optimum operating conditions for the reformer were determined to be 903 K and 0.11 g-sample g-catalyst− 1 h− 1 with a 5 wt.% Ru/γ-Al2O3 catalyst. The composition of the gas produced with the 5 wt.% catalyst was almost the same as that predicted by chemical equilibrium laws, and it was applicable for a direct hydrocarbon fuel cell.

SUMMARY AND CONCLUSIONS The effects of SO 2 concentration and particle size on sulphation of paper sludge ash were determined in a thermobalance reactor. The activation energy and the pre-exponential factor are found to be 33 172 kJ/kmol at 8.88 × 10 -6 s -1 Pa -1 based on the uniform-reaction model. The reaction order is found to be 1.0 at SO 2 partial pressures of 2000–7000 ppm. Compared with limestone, high sulphation conversion of the paper sludge ashes can be obtained regardless of their particle size.From the X-ray diffraction analysis, most of the sulphation compounds are observed to be CaSO 4 . The outer pore of the sludge ash is not blocked by CaSO 4 and the sulphation occurs uniformly throughout the ash. The uniform distributions of CaO and other inert minerals in the ash provide uniform sulphation with good penetration of SO 2 into pores of the sludge ash without pore blocking during sulphation of CaO. The CaO content in the paper sludge ash is about 1/3 of the limestone with high CaO content but, the sulphation conversion is about 1.5–2 times higher than that of the calcined limestone.

Combustion of spent vacuum residue hydrodesulfurization catalyst and incineration of paper sludge were carried out in thermo-gravimetric analyzer and an internally circulating fluidized-bed (ICFB) reactor. From the thermo-gravimetric analyzer-differential thermo-gravimetric curves, the pre-exponential factors and activation energies are determined at the divided temperature regions, and the thermo-gravimetric analysis patterns can be predicted by the kinetic equations. The effects of bed temperature, gas velocity in the draft tube and annulus, solid circulation rate, and waste feed rate on combustion efficiency of the wastes have been determined in an ICFB from the experiments and the model studies. The ICFB combustor exhibits uniform temperature distribution along the bed height with high combustion efficiency (>90%). The combustion efficiency increases with increasing reaction temperature, gas velocity in the annulus region, and solid circulation rate and decreases with increasing waste feed rate and gas velocity in the draft tube. The simulated data from the kinetic equation and the hydrodynamic models predict the experimental data reasonably well.

This paper considers the problem of determining the optimal number of redundant units in redundant systems with random unit failures and warranty. Parallel and k out of n systems are considered. The optimal number of redundant units which minimize the expected cost rate is found and the number is shown to be finite and unique. For given inspection interval before expiration of warranty, the optimal number of redundant units is also obtained. The effects of inspection and the warranty to the optimal number of redundant units are studied.

Pyrolysis kinetics of a pine nut shell in a thermo gravimetric analyzer (TGA) and the combustion and steam gasification kinetics of a pine nut shell’s chars in a thermobalance reactor were determined. Also, the steam gasification characteristics of the pine nut shell were determined in a fluidized bed reactor. The maximum pyrolysis reaction rate is obtained at 360oC from the TGA and DTG studies. The activation energy and the pre-exponential factor of the char were determined from the Arrhenius plot based on the shrinking core model. The effects of the reaction temperature (350oC - 950oC) and the O2 partial pressure on the combustion kinetics and that of the steam partial pressure (0.4 - 0.8atm) on the gasification kinetics were determined in a thermobalance reactor. In the combustion reaction, the activation energies and the pre-exponential factors are found to be 21.7 kcal mol-1 at 61.9 s-1atm-1 and 2.36 kcal/mol at 0.0029 s-1atm-1 in the reaction control and the pore-diffusion control regimes, respectively. The reaction order is found to be 1.0 with respect to the O2 partial pressure at 750oC. In the steam gasification reaction, the activation energy and the pre-exponential factor are found to be 16.9 kcal mol-1 at 0.0076s-1atm-1 and 2.67 kcal mol-1 at 0.00036s-1atm-1 in the reaction control and the pore-diffusion control regimes, respectively. The reaction order is found to be 0.77 with respect to the H2O partial pressure at 750oC. The effects of the gas velocity (2Umf - 4Umf), reaction temperature (700oC - 850oC), steam/carbon ratio (0.56 - 1.12) and O2/C ratio (0.16 - 0.32) on the gas composition, gas yield, cold gas efficiency and the calorific value of the product gas were determined in a fluidized bed reactor (10 cm-i.d. × 1.6m-high) with the feeding rate of the pine nut shell of 1 - 3 kg hr-1. The carbon conversion, calorific value, cold gas efficiency and the total product gas yield increased with an increasing temperature. The hydrogen concentration increases with an increasing reaction temperature and the gas velocity and steam/carbon ratio as well as the hydrogen concentration decreases with an increasing O2/C ratio in the fluidized bed reactor.

The selective catalytic reduction (SCR) of NOx by urea as a reducing agent was carried out over fresh and sulfated CuO/γ-Al2O3 catalysts in a fluidized-bed reactor. The optimum temperature ranges for NO reduction on the fresh and sulfated CuO/γ-Al2O3 catalysts were 300-350 ◦ C and 400-450 ◦ C, respectively. NO reduction with the sulfated CuO/γ-Al2O3 catalyst was somewhat higher than that with the fresh CuO/γ-Al2O3 catalyst. N2O formation increased with increasing reaction temperature. Ammonia (NH3) slip increased with increasing gas velocity and decreased with increasing reaction temperature.  2003 Society of Chemical Industry

Effects of superficial gas velocities to a draft tube, to an annulus section and particle size on the solid circulation rate (G,) have been determined in an internally circulating fluidized bed (0.28 m I.D. × 2m high) with an orifice type draft tube. The solid circulation rate from the draft tube to an annulus section increases with increasing gas velocities to the draft tube(U d ) and annulus section (Ua) and consequent increase in pressure drop across the orifice (ΔPor). However, the values ofG s decrease by 7–21% with increasing particle size from 86 to 288 μm. The pressure drop across the orifice increases with increasingU d andU a . However, ΔPor decreases by 5–23% with increasing particle size. To predictG s in an internally circulating fluidized bed, a correlation is proposed as a function of ΔPor

Automobile shredder residue (ASR) from end-of-life vehicles (ELVs) in Korea has commonly been disposed of in landfills. Due to the growing number of scrapped cars and the decreasing availability of landfill space, effective technology for reducing ASR is needed. However ASR is a complex mixture, and finding an appropriate treatment is not easy on account of the harmful compounds in ASR. Therefore, research continues to seek an effective treatment technology. However most studies have thus far been performed in the laboratory, whereas few commercial and pilot studies have been performed. This paper studies the pyrolysis and gasification-melting of ASR. The pyrolyis characteristics have been analyzed in a thermogravimetric analyzer (TGA), a Lindberg furnace, and a fixed-bed pyrolyzer to study the fundamental characteristics of ASR thermal conversion. As a pilot study, shaft-type gasification-melting was performed. High-temperature gasification-melting was performed in a 5000 kg/day pilot system. The gas yield and syngas (H2 and CO) concentration increase when the reaction temperature increases. Gas with a high calorific value of more than 16,800 kJ/m3 was produced in the pyrolyzer. From the gasification-melting process, syngas of CO (30-40%) and H2(10-15%) was produced, with 5% CH4 produced as well. Slag generation was 17% of the initial ASR, with 5.8% metal content and 4% fly ash. The concentration of CO decreases, whereas the H2, CO2, and CH4 concentrations increase with an increase in the equivalence ratio (ER). The emission levels of dioxin and air pollution compounds except nitrogen oxides (NO(x)) were shown to satisfy Korean regulations.

A simple expression for the apparent reaction rate of large wood char gasification with steam is proposed. Large char samples were gasified under steam atmosphere using a thermo-balance reactor. The apparent reaction rate was expressed as the product of the intrinsic rate and the effective factor. The effective factor was modified to include the effect of change in char diameter and intrinsic reaction rate during the reaction. Assuming uniform conversion ratio throughout a particle, the simplified reaction scheme was divided into three stages. In the initial stage, the local conversion ratio increases without particle shrinkage. In the middle stage, the particle shrinks following the shrinking core model without change in the local conversion ratio. In the final stage, the local conversion ratio increases without particle shrinkage. The validity of the modified effective value was confirmed by comparison with experimental results.

1. Abstract Pyrolysis kinetics of a gingko nut shell in a thermo gravimetric analyzer (TGA) and the steam gasification and combustion kinetics of chars from gingko nut shell in a thermobalance reactor have been determined. The effects of the reaction temperature (350 °C – 950 °C) and steam partial pressure (0.4 - 0.8 atm.) on the gasification kinetics and that of oxygen partial pressure (0.4 - 0.8 atm.) on the combustion kinetics have been determined in a thermobalance reactor. The activation energy and the pre-exponential factor were determined from the Arrhenius plot based on the shrinking core model. In the steam gasification reaction, the activation energy and the pre-exponential factor are found to be 40.8 kJ mol-1 at 1.7 s-1atm.-1, respectively. The reaction order is found to be 0.32 with respect to water partial pressure at 750 °C. In the combustion reaction, the activation energies and pre-exponential factors are found to be 92.8 kJmol-1 at 136.8 s-1atm-1 and 9.2 kJmol-1 at 0.012 s-1atm-1 in the reaction control and the pore-diffusion control regimes, respectively.

The effect of the additives on the selective non-catalytic reduction (SNCR) reaction has been determined in a three-stage laboratory scale reactor. The optimum reaction temperature is lowered and the reaction temperature window is widened with increasing concentrations of the gas additives (CO, CH 4 ). The optimum reaction temperature is lowered and the maximum NO removal efficiency decreases with increasing the concentration of alcohol additives (CH 3 OH, C 2 H 5 OH). The addition of phenol lowers the optimum reaction temperature about 100–150 °C similar to that of the toluene addition. The volatile organic compounds (VOCs: C 6 H 5 OH, C 7 H 8 ) can be utilized in the SNCR process to enhance NO reduction and removed at the same time. A previously proposed simple kinetic model can successfully apply the NO reduction by NH 3 and the present additives.

Financial supports from the National Sciences and Engineering Research Council of Canada and the Ministry of Science and Technology in Korea are acknowledged. Quebec’s Ministry of Education is acknowledged for the postdoctoral fellowship given to one of the authors (W. Namkung).

Plasma-assisted nitrogen fixation is a promising sustainable and clean alternative to the classical Haber–Bosch process. However, the high energy consumption and low production rate of plasma-assisted nitrogen fixation limit its application. This study shows that the non-thermal (non-equilibrium) enhancement of the arc plasma significantly reduces the energy consumption of nitrogen fixation. The highest energy efficiency with high NO selectivity is observed with a low specific energy input (SEI). However, the highest production rate is reached at a high SEI. The studied process offers high NO selectivity (up to 95%) with low energy consumption (∼48 GJ per tN) at 0.1 kJ L−1 SEI, which is much lower than the previously reported value of plasma-assisted atmospheric nitrogen fixation and is close to that of the Haber–Bosch process.