• Journal of Soil and Groundwater Environment
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• v.27 no.1
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• pp.17-24
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• 2022

This work examined the effect of mixing transition metal-based additives [FeCl₃, Fe-containing paper mill sludge (PMS), CoCl₂·H₂O, ZrO₂, and α-Fe₂O₃] on the thermochemical conversion of coffee waste (CW) in carbon dioxide-assisted pyrolysis process. Compared to the generation amounts of syngas (0.7 mole% H₂ & 3.0 mole% CO) at 700℃ from single pyrolysis of CW, co-pyrolysis in the presence of Fe- or Zr-based additives resulted in the enhanced production of syngas, with the measured concentrations of H₂ and CO ranging 1.1-3.4 mole% and 4.6-13.2 mole% at the same temperature, respectively. In addition, α-Fe₂O₃ biochar possessed the adsorption capacity of As(V) (19.3 mg g^-1) comparable to that of ZrO₂-biochar (21.2 mg g^-1). In conclusion, solid-type Fe-based additive can be highly considered as an efficient catalyst to simultaneously produce syngas (H₂ & CO) as fuel energy resource and metal-biochar as sorbent.

• Membrane Journal
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• v.33 no.3
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• pp.87-93
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• 2023

Electrodialysis (ED) is essential in separating ions through an ion exchange membrane. The disposal of brine generated from seawater desalination is a primary environmental concern, and its recycling through membrane separation technology is highly efficient. Alkali is produced by several chemical industries such as leather, electroplating, dyeing, and smelting, etc. A high concentration of alkali in the waste needs treatment before releasing into the environment as it is highly corrosive and has a chemical oxygen demand (COD) value. The concentration of calcium and magnesium is almost double in brine and is the perfect candidate for carbon dioxide adsorption, a major environmental pollutant. Sodium hydroxide is essential for the metal carbonation process which, is easily produced by the bipolar membrane electrodialysis process. Various strategies are available for its recovery, like reverse osmosis (RO), nanofiltration (NF), ultrafiltration (UF), and ED. This review discusses the ED process by ion exchange membrane for alkali recovery are discussed.

• Korean Chemical Engineering Research
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• v.62 no.1
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• pp.36-43
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• 2024

Fishing net waste (FNW) constitutes over half of all marine plastic waste and is a major contributor to the degradation of marine ecosystems. While current treatment options for FNW include incineration, landfilling, and mechanical recycling, these methods often result in low-value products and pollutant emissions. Importantly, FNWs, comprised of plastic polymers, can be converted into valuable resources like syngas and pyrolysis oil through pyrolysis. Thus, this study presents a process for generating high-purity hydrogen (H₂) by catalytically pyrolyzing FNW in a CO₂ environment. The proposed process comprises of three stages: First, the pretreated FNW undergoes Ni/SiO₂ catalytic pyrolysis under CO₂ conditions to produce syngas and pyrolysis oil. Second, the produced pyrolysis oil is incinerated and repurposed as an energy source for the pyrolysis reaction. Lastly, the syngas is transformed into high-purity H₂ via the Water-Gas-Shift (WGS) reaction and Pressure Swing Adsorption (PSA). This study compares the results of the proposed process with those of traditional pyrolysis conducted under N₂ conditions. Simulation results show that pyrolyzing 500 kg/h of FNW produced 2.933 kmol/h of high-purity H₂ under N₂ conditions and 3.605 kmol/h of high-purity H₂ under CO₂ conditions. Furthermore, pyrolysis under CO₂ conditions improved CO production, increasing H₂ output. Additionally, the CO₂ emissions were reduced by 89.8% compared to N₂ conditions due to the capture and utilization of CO₂ released during the process. Therefore, the proposed process under CO₂ conditions can efficiently recycle FNW and generate eco-friendly hydrogen product.

• Journal of Korean Society of Environmental Engineers
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• v.29 no.9
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• pp.1027-1034
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• 2007

This research was focused on the selective separation of $CO_2$ or $CH_4$ from mixture of these gases, by controlling the size of pore or pore gate. Pitch based activated carbon fibers(ACF) were used as adsorbents. The size of pore gate was controlled by the molecule having similar size to that of pore opening. After the adsorption of adsorbate on pore surface, planar molecules such as benzene and naphthalene covered the pore gate. The slow release of adsorbate from the pores covered by planar molecules makes apertures between planar molecules covering pore gate and this structure can be fixed by rapid pyrolysis. The control of pore gate using benzene as covering molecules could not accomplished due to the simultaneous volatilization of benzene and adsorbate$(CO_2)$ caused by similar temperatures of benzene volatilization and adsorbate desorption. Therefore we replaced benzene with naphthalene looking for the stability at a $CO_2$ desorption temperature. The naphthalene molecule was adsorbed on the ACF up to 15% of ACF weight and showed no desorption until $100^{\circ}C$, indicating that the molecule could be used as a good cover molecule. Naphthalene could cover almost all the pore gate, reducing BET surface area from 753 $m^2/g$ to 0.7 $m^2/g$. A mixed gas$(CO_2:CH_4=50:50)$ was adsorbed on the naphthalene treated OG-7A ACF. The amount of $CO_2$ adsorption increased with total pressure, whileas thai of $CH_4$ was not so much influenced on the pressure, indicating that $CO_2$ made more compounds on the ACF surface along with total pressure increase. The most $CO_2$ and the least $CH_4$ were adsorbed in the condition of 0.4 atm, resulting in the highly pure $CH_4$ left in ACF.

• Journal of Energy Engineering
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• v.25 no.4
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• pp.13-29
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• 2016

In this study, we analyzed the causes of major faults in the biogas plant through the case of gas engine failure when cogenerating electricity and heat using biogas as a fuel in the actual sewage treatment plant and suggested countermeasures. Hydrogen sulfide in the biogas entering the biogas engine and water caused by intermittent malfunction of the water removal system caused intercooler corrosion in the biogas engine. In addition, the siloxane in the biogas forms a silicate compound with silicon dioxide, which causes scratches and wear of the piston surface and the inner wall of the cylinder liner. The substances attached to the combustion chamber and the exhaust system were analyzed to be combined with hydrogen sulfide and other impurities. It is believed that hydrogen sulfide was supplied to the desulfurization plant for a long period of time because of the high content of hydrogen sulfide (more than 50ppm) in the biogas and the hydrogen sulfide was introduced into the engine due to the decrease of the removal efficiency due to the breakthrough point of the activated carbon in the desulfurization plant. In addition, the hydrogen sulfide degrades the function of the activated carbon for siloxane removal of the adsorption column, which is considered to be caused by the introduction of unremoved siloxane waste into the engine, resulting in various types of engine failure. Therefore, hydrogen sulfide, siloxane, and water can be regarded as the main causes of the failure of the biogas engine. Among them, hydrogen sulfide reacts with other materials causing failure and can be regarded as a substance having a great influence on the pretreatment process. As a result, optimization of $H_2S$ removal method seems to be an essential measure for stable operation of the biogas engine.

• Journal of the Korean Applied Science and Technology
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• v.31 no.2
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• pp.320-328
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• 2014

Biodiesel has very similar physical properties (density, kinematic viscosity) and has even higher cetane number compare with conventional diesel. There are no necessity to change or modify the infra-structure & engine system. It is known that fatty acid methyl ester (FAME) is oxygen-contained components increasing the combustibility, biodegradability and reduced the exhaust harmful gas. These things made the biodiesel more popular as an alternative diesel fuel. But biodiesel's sources are controversial issues about $CO_2$ reduction effect at this time because those mainly come from edible plants such as soy, palm, rapeseed already spent lot of $CO_2$ to cultivate. Whereas micro-algae is focused because they are inedible and has rapid growth rates & high carbon-dioxide adsorption rate per area. In this study, we analyze the each FAME components using $GC{\times}GC$-TOFMS in stead of GC-FID and verify the previous total FAME contents method's applicability through the micro algal biodiesel derived from Dunaliella tertiolecta.

• Korean Chemical Engineering Research
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• v.55 no.1
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• pp.60-67
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• 2017

In this study, we performed surface modification of biodegradable microcrystalline cellulose (MCC) to use as a filler in polyethylene (PE) composite in food packaging application. We modified MCC surface with (3-trimethoxysilylpropyl)diethylenetriamine (TPDT) silane coupling agent, which has one primary amino group and two secondary amino groups per molecule, to introduce amino groups with a carbon dioxide adsorption capability in MCC. Effects of each of the reaction conditions such as amount of TPDT introduced, swelling time, reaction temperature, and reaction time on surface modification degree of MCC were investigated by changing a variety of above reaction conditions. The amount of TPDT grafted on MCC surface and formation of chemical bonds were confirmed by Fourier transform infrared spectroscopy (FT-IR), elemental analysis (EA), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA) and solid state $^{29}Si$ nuclear magnetic resonance (NMR) spectroscopy. We confirmed increase of grafted amount of TPDT on MCC with increasing reaction time, reaction temperature, and amount of introduced TPDT.