• 한국자동차공학회논문집
• /
• 제15권4호
• /
• pp.146-153
• /
• 2007

The detailed chemistry with reaction mechanism of GRI 2.11, which consists of 49 species and 279 elementary reactions, have been numerically conducted to investigate the flame structure and NO emission characteristics in a non-premixed counterflow flame of blended fuel of $H_2/CO_2/Ar$. The combination of $H_2,\;CO_2$, and Ar as fuel is selected to clearly display the contribution of hydrocarbon products to flame structure and NO emission characteristics due to the breakdown of $CO_2$. Radiative heat loss term is involved to correctly describe the flame dynamics especially at low strain rates. All mechanisms including thermal, $NO_2,\;N_2O$, and Fenimore are also taken into account to separately evaluate the effects of $CO_2$ addition on NO emission characteristics. The increase of added $CO_2$ quantity causes flame temperature to fall since at high strain rates diluent effect is prevailing and at low strain rates the breakdown of $CO_2$ produces relatively populous hydrocarbon products and thus the existence of hydrocarbon products inhibits chain branching. It is also found that the ratio of the contribution by Fenimore mechanism to that by thermal mechanism in the total mole production rate becomes much larger with increase in the $CO_2$ quantity and strain rate, even though the absolute quantity of NO production is deceased. Consequently, as strain rate and $CO_2$ quantity increase, NO production by Fenimore mechanism is remarkably augmented.

• 한국해양환경ㆍ에너지학회지
• /
• 제3권2호
• /
• pp.3-10
• /
• 2000

1999년 4월, 8월과 11월에 금강 하구역 갯벌 세 지점에서 채니된 퇴적물 표층 5 cm을 입도 조성 분석한 결과 모래와 자갈 성분이 1.18 %, 모래 성분이 29.34 %, 점토 성분이 69.49 %였다. 퇴적물의 IL은 6.7 %, ORP는 -12 mV으로 약간의 환원상태를 보이고 있었다. 퇴적물 중 H₂S 농도는 평균 0.25 mg/gㆍdry으로 측정되었다 금강 하구 갯벌 퇴적물에서의 탈질산화는 4월에 0.186 m mole N₂/m²ㆍday, 8월에 0.192 m mole N₂/m²ㆍday, 11월에 91.3 m mol N₂/m²ㆍday으로 3회 평균 30.6 m mole N²/m²ㆍday였다. 퇴적물과 수층간의 NH₄/sup +/-N의 플럭스는 4월에 -0.37 m mole N/m²ㆍday, 8월에 34.0 m mole N/m²ㆍday, 11월에 0.10 m mole N/m²ㆍday으로 평가되어 평균적으로 11.2 m mole N/m²ㆍday였다. 한편, 퇴적물과 수층간의 NO²/sup -/-N+ NO₃/sup -/-N의 플럭스는 4월에 0.314 m mole N/m²ㆍday, 8월에 0.524 m mole N/m²ㆍday, 11월에 -4.12 m mole N/m²ㆍday으로 측정되어 평균 -1.09 m mole N/m²ㆍday으로 측정되어졌다. 암모니아질소와 아질산질소 및 질산질소의 플럭스로부터 계산한 용존무기질소 (DIN)의 플럭스는 10.2 m mole N/m²ㆍday으로 평가되었다. 이와 같은 금강하구역 갯벌에서의 용존성무기질소의 플럭스와 탈질산화는 이 해역의 질소수지와 1차 생산에 중요한 영향을 끼칠 것으로 추정되었다.

• 한국표면공학회지
• /
• 제26권2호
• /
• pp.87-107
• /
• 1993

The grain size of the final products of WC-Co and WC-Ni composite powders is dependent on the size of the starting material and the conditions employed for the reduction and carburization. APT-Co and -Ni com-plex salts were prepared by the substitution reaction between ammonium ions in APT and the metal ions in Co(NO3)2 and Ni(NO3)2 solutions of different concentrations(0.1 to 0.7M) at $50^{\circ}C$ and the grain sizes of the com-plex salts was $0.54~0.76\mu\textrm{m}$. The complex which calcined the complex salts at $700^{\circ}$~80$0^{\circ}C$ for 60min. were 0.2~0.5$\mu\textrm{m}$. W-Co($5.92^{\circ}C$) and -Ni(6.95%) powders which reduced the complex oxides with H2d atmo-sphere(flow rate;600cc/min.) at $700^{\circ}$~$800^{\circ}C$ for 60min. were $0.5~0.6\mu\textrm{m}$. The mean grain sizes of WC-Co and WC-Ni composite powders which carburized both complex metals of W-Co and W-Ni at $800^{\circ}C$ for 60min. were $0.5~0.6\mu\textrm{m}$, and take place the coarsening of the grain above $800^{\circ}C$ and the optmium ratio of C3H8 and H2 was 0.2 for the control of the free carbon. The effect of Co contents on the particle sizes decreased from 0.4 to $0.25\mu\textrm{m}$ with increasing the content from 2.0 to 7.6w%. The activation energies on the reductions of oxides and the formations of carbides were as follows ; W-Co : Q = 8.7 kcal/mole, W-Ni : Q = 8.1 kcal/mole, WC-Co pow-der : Q = 17.8 kcal/mole, WC-Ni powder : Q = 16.6 kcal/mole.

• 대한기계학회논문집B
• /
• 제32권8호
• /
• pp.604-611
• /
• 2008

Detailed analysis of NO formation routes and its contributions with strain rate in hydrogen/air flames were numerically investigated. LiG detailed reaction mechanism has been used for calculation, which is compared with experimental data in literature. It shows good agreement with experiment for both temperature and NO mole fraction. Three routes have been found important for NO formation in hydrogen flames. These are the Thermal route, NNH route and $N_2O$ route. Strain rate were varied to discuss the $EI_{NO}$ reduction trend in hydrogen nonpremixed flames, which are analyzed by each NO formation routes. As a result, as the strain rate increase, $EI_{NO}$ decrease sharply until strain rate $100s^{-1}$ and decrease slowly until strain rate $310s^{-1}$ again, after that $EI_{NO}$ keeps nearly constant. It can be identified that $EI_{NO}$ trend with the strain rate is well explained by a combination of variation of production rate of above Thermal, NNH and $N_2O$ route. Also result of Thermal-Mech. that includes only thermal NO reaction is compared with those of Full-Mech. As a result, It can be identified that there was difference between the two results of calculation. It is attributed to result that Thermal-mech did not consider contributions of NNH and $N_2O$ route. From these result, we can conclude that NOx emission characteristics of hydrogen nonpremixed flames should consider contributions of above three routes simultaneously.

• 한국가스학회지
• /
• 제23권6호
• /
• pp.8-16
• /
• 2019

저공해 연소를 위한 방법 중 하나인 배기가스 재순환(flue gas recirculation, 이하 FGR)은 질소산화물 저감에 효과적인 연소 기법이다. 이를 메탄/공기 대향류 예혼합화염에 적용하여 화염의 특성변화와 NOx 생성 기구를 파악하기 위한 수치해석을 진행하였다. 신장률에 따라 배출되는 생성물들의 몰분율이 달라진다는 점을 고려하여 재순환율은 생성물을 기준으로 정의되었으며, 실제 연소 시스템을 반영하기 위해 주요 생성물인 CO₂, H₂O, O₂ 그리고 N₂를 희석제로써 재순환하였다. FGR 기법이 적용됨에 따라 특정한 신장률 조건에서 최대화염 온도의 전환점이 발견되었다. 또한, 재순환율이 증가함에 따라 온도와 NO의 경향이 달리 나타났으며, 이를 파악하고자 NO 반응을 열적 NO와 Fenimore NO로 구분하여 분석하였다.

• Applied Biological Chemistry
• /
• 제33권2호
• /
• pp.109-115
• /
• 1990

대두 STI의 열처리에 의한 불활성화에 L-cysteine 및 sodium sulfite의 첨가 효과를 조사하고, 대두 품종별 STI활성을 측정하였으며 활성도와 단백질 및 cysteine함량 그러고 소화율과의 관계를 비교하였다. 열처리에 의한 STI의 불활성화에 L-cysteine과 sodium sulfite의 첨가는 불활성화 효과를 크게 증가시켰으며 대두 품종간 불활성화 정도는 차이를 보이지 않았으며 L-cysteine과 sodium sulfite의 첨가는 불활성화된 STI의 재활생화를 크게 억제하였다. 품종별 STI의 활성도는 대두분말 g당 $64.7{\sim}86.47\;TIU$의 범위에 있었으며, 장백>힐>장엽, 광교>단엽>백운>단경>팔달, 새알, 덕유>황금 이었으며, 단백질 함량과 STI의 활성도와는 상관관계(r=-0.192)가 없는 것으로 나타났다. 품종별 cysteine 함량은 힐, 장백, 단경, 단엽, 황금, 백운, 장엽, 새알, 덕유, 광교, 활달의 순서이었으며, cysteine의 함량은 $73.5{\sim}40.0\;{\mu}mole/g$ 대두분 이었다. 또한 cysteine함량과 STI 활성도 사이에 정의 상관(r=0.6568)을 나타냈다. 품종별 소화율은 광교, 백운, 팔달, 단경, 새알, 힐, 장엽, 덕유, 황금, 장백, 단엽의 순서이었으며 $81.9{\sim}76.7%$ 정도이었다. 또한 소화율과 STI활성도 사이에는 부의 상관(r=-0.7695)을 나타내었다.

• Environmental Analysis Health and Toxicology
• /
• 제19권1호
• /
• pp.33-40
• /
• 2004

Benzoyl peroxide is a High Production Volume Chemical, which is produced about 1,371 tons/year in Korea as of 2001 survey. The substance is mainly used as initiators in polymerization, catalysts in the plastics industry, bleaching agents for flour and medication for acne vulgaris. In this study, Quantitative Structure-Activity Relationships (QSAR) are used for getting adequate information on the physical -chemical properties of this chemical. And hydrolysis in water, acute toxicity to aquatic and terrestrial organisms for benzoyl peroxide were studied. The physical -chemical properties of benzoyl peroxide were estimated as followed; vapor pressure=0.00929 Pa, Log $K_{ow}$ = 3.43, Henry's Law constant=3.54${\times}$10$^{-6}$ atm-㎥/mole at $25^{\circ}C$, the half-life of photodegradation=3 days and bioconcentration factor (BCF)=92. Hydrolysis half-life of benzoyl peroxide in water was 5.2 hr at pH 7 at $25^{\circ}C$ and according to the structure of this substance hydrolysis product was expected to benzoic acid. Benzoyl peroxide has toxic effects on the aquatic organisms. 72 hr-Er $C_{50}$ (growth rate) for algae was 0.44 mg/1.,48 hr-E $C_{50}$ for daphnia was 0.07mg/L and the 96hr-L $C_{50}$ of acute toxicity to fish was 0.24mg/L. Acute toxicity to terrestrial organisms (earth worm) of benzoyl peroxide was low (14 day-L $C_{50}$ = > 1,000 mg/kg). Although benzoyl peroxide is high toxic to aquatic organisms, the substance if not bioaccumulated because of the rapid removal by hydrolysis (half-life=5.2 hr at pH 7 at $25^{\circ}C$) and biodegradation (83% by BOD after 21 days). The toxicity observed is assumed to be due to benzoyl peroxide rather than benzoic acid, which shows much lower toxicity to aquatic organisms. One can assume that effects occur before hydrolysis takes place. From the acute toxicity value of algae, daphnia and fish, an assessment factor of 100 was used to determine the predicted no effect concentration (PNEC). The PNEC was calculated to be 0.7$\mu\textrm{g}$/L based on the 48 hr-E $C_{50}$ daphnia (0.07 mg/L). The substance shows high acute toxicity to aquatic organisms and some information indicates wide-dispersive ore of this substance. So this substance is, a candidate for further work, even if it hydrolysis rapidly and has a low bioaccumulation potential. This could lead to local concern for the aquatic environment and therefore environmental exposure assessment is recommended.