• Journal of the Korean GEO-environmental Society
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• v.11 no.11
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• pp.27-36
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• 2010

This study was conducted to evaluate physicochemical parameters; temperature, pH, C/N ratio, water content, organic contents and volume in a pilot-scale(capacity : $100m^3$) ultra thermophilic aerobic composting. There were three types input: municipal wasted sludge, livestock manure and slurry, and food waste produced in Jung-Eb city. Each target material was carried out by the first fermentation(organic waste + seed culture) and the second one(organic waste + seed culture + recycle compost), respectively. During composting, only with supply of air and mixing, the temperature increased $90{\sim}105^{\circ}C$ after every mixing in both periods. The changes of pH, $O_2$, $CO_2$ and $NH_3$ represented typical organic decomposition pattern by microorganisms. Also, all other physicochemical parameters of ultra thermophilic aerobic composting process showed similar or better performance than these of general aerobic composting. Heavy metal concentration of fermented compost adapted to compost fertilizer regulation standard in the heavy metal and hazardous analysis.

• Journal of the Korean Ceramic Society
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• v.40 no.9
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• pp.891-896
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• 2003

Novel fabrication technique was developed for high strength Reaction-Bonded SiC (RBSC) hot gas filter for use in IGCC (Integrated Gasification Combined Cycle) system. The room and high temperature fracture strengths for Si-melt infiltrated reaction-bonded SiC were 50-123, and 60-66 MPa, respectively. The average pore size was 60-70 $\mu\textrm{m}$ and the porosity was about 34 vol％. RBSC infiltrated with molten silicon showed improved fracture strength at high temperature, as compared to that of clay-bonded SiC, due to SiC/Si phase present within SiC phase. The thickness for SiC/Si phase was increased with increasing powder particle size of SiC from 10 to 34 $\mu\textrm{m}$. Pressure drop with dust particles showed similar response as compared to that for Schumacher type 20 filter. The filter fabricated in the present study showed good performance in that the filtered powder size was reduced drastically to below 1 $\mu\textrm{m}$ within 4 min.

• Resources Recycling
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• v.4 no.1
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• pp.31-37
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• 1995

This study was to investigate the effects oi agitation speed, pulp concentration, ion concentration ill the slurry solution, printed area of the waste newspaper, immerwng time and the temperature on the defiberation process for the waste newspaper. The defikration efficiency at 50% is twice that of 16%. The efficiency is improved as two times according to elevate the agtation speed as two times in the range of 200-2WO r.p.m.. Defiberation with NaOH 1X10-'M solution has higher efficiency than that of NaOH 1 x 1 0 - M solution as 3 times at the conditions of 16%, 1200 r.p.m, and 1% pulp concentration The temperature of immersing salut~on aifects on the efficiency more than immersing time does. Increasing the printed area of newspaper decreases the velocity of defiberation. The alkaline solution is effective to defiberate and the defiberation efficiency at the same dosage of alkalinity is in the order a1 NaOH) KOH) Na,SiO, ) Na,CO, ) Ca(OH)2.

• Journal of the Korea Organic Resources Recycling Association
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• v.23 no.4
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• pp.95-103
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• 2015

The purpose of this study was performed to quantitatively measure the thermal conductivity of poultry slaughter waste with variation of reaction temperature for optimal design of thermal hydrolysis reactor. We continuously quantified the thermal conductivity of dehydrated sludge related to the reaction temperature. As the reaction temperature increased, the dehydrated sludge is thermally liquefied under high temperature and pressure by the thermal hydrolysis reaction. Therefore, the bond water in the sludge cells comes out as free water, which changes the dehydrated sludge from a solid phase to slurry of a liquid phase. As a result, the thermal conductivity of the its sludge was more than 2.11 times lower than that of the water at $20^{\circ}C$. However, the thermal conductivity of the sludge approached to $0.677W/m{\cdot}^{\circ}C$ of water at $200^{\circ}C$, experimentally substantiating liquefaction of the dehydrated sludge. Therefore, we confirmed that the change in physical properties due to thermal hydrolysis appears to be an important factor for heat transfer efficiency. And the thermal conductivity function related to reaction temperature was derived to give the boundary condition for the optimal design of the thermal hydrolysis reactor. The consistency of the calculated function was 99.69%.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.101-101
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• 2010

Anaerobic digestion(AD) is the most promising method for treating and recycling of different organic wastes, such as organic fraction of municipal solid waste, household wastes, animal manure, agro-industrial wastes, industrial organic wastes and sewage sludge. During AD, i.e. organic materials are decomposed by anaerobic forming bacteria and fina1ly converted to excellent fertilizer and biogas which is a mixture of carbon dioxide and methane. AD has been one of the leading technologies that can make a large contribution to produce renewable energy and to reduce $CO_2$ and other green-house gas(GHG) emission, it is becoming a key method for both waste treatment and recovery of a renewable fuel and other valuable co-products. Currently some 80% of the world's overall energy supply of about 400 EJ per year in derived from fossil fuels. Nevertheless roughly 10~15% of this demand is covered by biomass resources, making biomass by far the most important renewable energy source used to date. The representative biofuels produced from the biomass are bioethanol, biodiesel and biogas, and currently biogas plays a smaller than other biofuels but steadily growing role. Traditionally anaerobic digestion applied for different biowaste e.g. sewage sludge, manure, other organic wastes treatment and stabilization, biogas has become a well established energy resource. However, the biowaste are fairly limited in respect to the production and utilization as renewable source, but the plant biomass, the so called "energy crops" are used for more biogas production in EU countries and the investigation on the biomethane potential of different crops and plant materials have been carried out. In Korea, with steadily increasing oil prices and improved environmental regulations, since 2005 anaerobic digestion was again stimulated, especially on the biogasification of different biowastes and agro-industrial biomass including "energy crops". This study have been carried out to investigate anaerobic biodegradability by the biochemical methane potential(BMP) test of animal manures, different forage crops i.e. "energy crops", plant and industrial organic wastes in the condition of thermophilic temperature, The biodegradability of animal manure were 63.2% and 58.2% with $315m^3CH_4/tonVS$ of cattle slurry and $370m^3CH_4/tonVS$ of pig slurry in ultimate methane yields. Those of winter forage crops were the range 75% to 87% with ultimate methane yield of $378m^3CH_4/tonVS$ to $450m^3CH_4/tonVS$ and those of summer forage crops were the range 81% to 85% with ultimate methane yield of $392m^3CH_4/tonVS$ to $415m^3CH_4/tonVS$. The forge crops as "energy crops" could be used as good renewable energy source to increase methane production and to improve biodegradability in co-digestion with animal manure or only energy crop digestion.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.17 no.2
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• pp.63-68
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• 2007

A number of process problems should be solved in the multi-layered ceramic devices such as EMI filter. In particular, it is essential to control the sintering shrinkage in co-firing of different materials for obtaining defect-free samples such as crack, camber, and delamination which usually occur near the surface and interface. We studied the effect of the powder properties of ferrite on the co-firing behavior of green ceramic layers composed of ferrite and varistor. Three kind of ferrite powder samples as a function of milling time (24, 48, and 72 hr) were prepared. Varistor and ferrite ceramic green sheet were made by means of doctor blade process using slurry (ceramic powder and binder solution). Here, slurry was prepared by mixing 55 wt% powder with 45wt% binder solution. Varistor and ferrite green sheets were laminated at $80 kg/cm^2$, and co-fired at $900^{\circ}C$ and $1000^{\circ}C$ for 3 hr. We obtained the camber-free and co-fired ferrite/varistor layer structure by controlling the milling time and sintering temperature.

• Applied Chemistry for Engineering
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• v.10 no.2
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• pp.293-298
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• 1999

Reaction mechanism was elucidated and reaction condition were optimized for the catalytic reaction synthesizing 2-methyl-4-methoxy-diphenylamine (MMDPA) which is an intermediate of Fluoran heat-sensitive dyestuff. Reactants consisted of 2-methyl-4-methoxyaniline (MMA), 3-methyl-4-nitroanisole (MNA), and cyclohexanone, and 5 wt % Pd/C was used as a catalyst. Experiments were run in an open slurry reactor equipped with reflux condenser, and products were analyzed by means of GC/MS and NMR. MMDPA yield of 90 mole % could be obtained after reaction time of 8~10 hours under the optimal reaction conditions comprising the reaction mass composition of MMA : MNA : cyclohexanone = 1 : 2 : 150 based on MMA input of 0.01 gmoles in xylene solvent, reaction temperature of $160^{\circ}C$, and catalyst amount of 0.5 g. It was found that the rate-determining step of overall reaction was dehydrogenation of the intermediate product obtained from condensation of MMA and cyclohexanone. Overall reaction rate and MMDPA yield were enhanced owing to hydrogen transfer reaction by introducing MNA together with MMA in the reaction mass. Excess cyclohexanone in the reaction mass played an important role of promoting the condensation of MMA and cyclohexanone.

• Journal of the Korean Electrochemical Society
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• v.19 no.2
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• pp.50-56
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• 2016

Spherical lithium manganese oxide spinel, $Li_{1.10}Mn_{1.86}Al_{0.02}Mg_{0.02}O_4$ was prepared by wet-milling, spray-drying, and sintering process. In the spray-drying process, solid content in slurry was varied from 20 to 30 wt%. In the sintering process, the precursors have been sintered under air or $O_2$ atmosphere. While the as-prepared samples exhibit excellent electrochemical properties at room temperature, the discharge voltage profiles at 5.0C are very different one from another. The origin for the difference especially at initial state of discharge is oxygen defect. The sample prepared in air has larger capacity related to the plateau at 3.3 V (vs. $Li/Li^+$) which is caused by the oxygen defects than the one prepared in $O_2$. The difference of discharge voltage profiles especially at the final state of discharge comes from different diffusion rate of $Li^+$ ions. The sample prepared from 30 wt% solid content of slurry shows twice higher diffusion rate than the samples prepared from 20 wt% solid content, which is attributed to better compactness between primary particles for the sample prepared from 30wt % solid content than the one prepared by 20 wt%.

• The Journal of Engineering Research
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• v.5 no.1
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• pp.73-87
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• 2004

The synthesis and crystallization of amorphous calcium carbonate($CaCO_3$.$nH_2 O$) obtained from gas-liquid reaction between aqueous solution of calcium hydroxide and carbon dioxide at 15~$50^{\circ}C$ are investigated by electrical conductometry, XRD and TEM. The results are as follows: The initial reaction products prior to the formation of precipitated calcium carbonate is amorphous calcium carbonate. The electrical conductivity values in the slurry are decreased during the formation of amorphous calcium carbonate which covers particle surface of calcium hydroxide and retard the dissolution of calcium hydroxide into the solution. that amorphous calcium carbonate is unstable in the aqueous solution and crystallizes finally to calcite by the through-solution reaction. While amorphous calcium carbonate crystallizes into chain-like calcite, the conductivity values are recovered rapidly and the apparent viscosity of slurry containing higher concentration of calcium hydroxide increase. At below pH 9.5, chain-like calcite separates into individual particles to form precipitated calcium carbonate. The formation and synthetic temperature range of amorphous calcium carbonate is most suitable a primary decreasing step(a-step) at $15^{\circ}C$ in the electrical conductometry.

• Clean Technology
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• v.15 no.4
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• pp.258-264
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• 2009

Thermodynamic measurements were performed to show the possibility of recovering $CO_2$ from fuel gas (the mixture of $CO_2$ and $H_2$) by forming gas hydrates with water where water was dispersed in the pores of silica gel particles having nominal 100 nm of pore diameter. The hydrate-phase equilibria for the ternary $CO_2+H_2$+water in pores were measured and $CO_2$ concentrations in vapor and hydrate phase were determined under the hydrate-vapor two phase region at constant 274.15 K. It was shown that the inhibition effect appeared due to silica gel pores, and the corresponding equilibrium dissociation pressures became higher than those of bulk water hydrates at a specific temperature. In addition, direct measurement of $CO_2$ content in the hydrate phase showed that the retrieved gas from the dissociation of hydrate contained more than 95 mol% of $CO_2$ when 42 mol% of $CO_2$ and balanced Hz mixture was applied. Compared with data obtained in case of bulk water hydrates, which showed just 83 mol% of $CO_2$ where 2-stage hydrate slurry reactor was intended to utilize this property, the hydrate formation in porous silica gel has enhanced the feasibility of $CO_2$ separation process. Hydrate formation as not for slurry but solid particle makes it possible to used fixed bed reactor, and can be a merit of well-understood technologies in the industrial field.