• Bulletin of the Korean Chemical Society
• /
• 제17권9호
• /
• pp.798-802
• /
• 1996

The photochemical decomposition of aqueous ammonia in the absence (saturated with argon) and the presence of O2 (saturated with air or oxygen) has been investigated using 184.9 nm UV light. The decomposition of ammonia depended on the concentration of oxygen in the solution. With increasing the concentration of oxygen, the decomposition of ammonia diminishes. Hydrazine is found the major product from the irradiation. In the presence of oxygen, hydrogenperoxide was also produced. The product yields depended also on the concentration of oxygen in the solution. The initial quantum yield of the products and of the ammonia decomposed were determined. Probable reaction mechanisms for the reaction were presented from the products analysis.

• Bulletin of the Korean Chemical Society
• /
• 제29권3호
• /
• pp.555-561
• /
• 2008

In air stripping of ammonia from the aqueous solution, a new removal model was presented considering the equilibrium principles for the ammonia in aqueous solution and between the aqueous and air phase. The effects of pH, temperature and airflow rate on the ammonia removal were evaluated with the model. In addition, the saturation degree of ammonia in air was defined and used to evaluate the effect of each experimental factor on the removal rate. As pH (8.9 to 11.9) or temperature (20 to 50 oC) was increased, the overall removal rate constants in all cases were appeared to be increased. Our presented model shows that the degrees of saturation were about the same (0.45) in all cases when the airflow condition remains the same. This result indicates that the effect of pH and temperature were directly taken into consideration in the model equation. As the airflow increases, the overall removal rate constants were increased in all cases as expected. However, the saturation degree was exponentially decreased with increasing the airflow rate in the air phase (or above-surface) aeration. In the subsurface aeration the saturation degree remains a constant value of 0.65 even though the airflow rate was increased. These results indicate that the degree of saturation is affected mainly by the turbulence of the aqueous solution and remains the same above a certain airflow rate.

• 한국신재생에너지학회:학술대회논문집
• /
• 한국신재생에너지학회 2011년도 춘계학술대회 초록집
• /
• pp.179.1-179.1
• /
• 2011

Pretreatment of cellulosic biomass is necessary before enzymatic saccharification and fermentation. The objective of this study was to evaluate the effect of combined aqueous ammonia-dilute sulfuric acid treatment on cellulosic biomass. Miscanthus was pretreated using aqueous ammonia and dilute sulfuric acid solution under high temperature and pressure conditions to be converted into bioethanol. Aqueous ammonia treatment was performed with 15 %(w/w) ammonia solution at $150^{\circ}C$ of reaction temperature and 20 minutes of reaction time. And then, dilute sulfuric acid treatment was performed with 1.0 %(w/w) sulfuric acid solution at $150^{\circ}C$ of reaction temperature and 10 minutes of reaction time. The compositional variations of this combined aqueous ammonia-dilute sulfuric acid treatment resulted in 68.0 % of cellulose recovery and 95.7 % of hemicellulose, 81.3 % of lignin, 89.1 % of ash removal respectively. The enzymatic digestibility of 90.5 % was recorded in the combined pretreated Miscanthus sample and it was 14.7 times higher than the untreated sample. The ethanol yield in the Simultaneous Saccharification and Fermentation was 90.4 % of maximum theoretical yield based on cellulose content of the combined pretreated sample and it was about 98 % compared to the ${\alpha}$-cellulose ethanol yield.

• Journal of Photoscience
• /
• 제6권4호
• /
• pp.177-181
• /
• 1999

The photochemical transformation of carbon monoxide in aqueous ammonia solution has been investigated at 25${\pm}$0.1$^{\circ}C$ using 184.9 nm UV light. Amination and carbonylation processes were carried out by irradiating the aqueous ammonia solution saturated with carbon monoxide, and the formation of formamide, urea, hexamethylenetetramine, formaldehyde, glyoxal and hydrazine was observed. The formation of hydrazine was affected by the presence of ammonia, and the formation of carbonyl compounds such as formaldehyde and glyoxal was influenced by the presence of carbon monoxide. The formation of formamide, urea and hexamethylenetetramine was affected by both ammonia and carbon monoxide. The initial quantum yields of the products were determined and probable mechanisms for the photochemical reaction were presented on the basis of product analysis.

• Korean Chemical Engineering Research
• /
• 제53권4호
• /
• pp.417-424
• /
• 2015

본 연구에서는 목질계 바이오매스인 돼지감자 줄기에 대한 전처리 공정을 수행하였다. 공정은 효소 당화 수율을 높이기 위하여 흐름형 침출 전처리 공정에 2단 전처리 공정으로 적용하였다. 전처리 용매로 암모니아수에 의한 탈 리그닌 효과와 황산 용액에 의한 헤미셀룰로오스의 분해가 효소당화 및 발효에 미치는 영향을 확인하였다. 암모니아수와 황산용액을 이용한 2단 전처리 공정을 수행하였다. 먼저 1단계 공정은 40분 동안 $163.2^{\circ}C$의 온도에서 암모니아수로 처리를 진행하였고 다음 2단계 공정은 $169.7^{\circ}C$에서 20분 동안 황산 용액으로 처리를 수행하여 물질수지를 구하였다. 그리고 앞의 공정과 반대의 순서로 황산 용액을 먼저 처리한 후 암모니아수를 처리한 2단 전처리 공정을 수행하였다. 이때 암모니아수를 먼저 처리한 공정에서 글루코오스 생산량은 30.7 g으로 72.4%의 수율이 나타났다. 반대로 황산 용액을 먼저 처리한 후 암모니아수를 처리한 2단 전처리 공정에서는 글루코오스 생산량이 20.9 g으로 49.3%의 수율을 보였다.

• 한국전기전자재료학회논문지
• /
• 제13권5호
• /
• pp.451-457
• /
• 2000

Experimental investigations on the effect of two kinds of additives ; aqueous NaOH solution and ammonia(NH$_3$) for removal of NOx and SO$_2$ simultaneously by corona discharge were carried out. The simulated combustion flue gas was[NO(0.02[%])-SO$_2$(0.08[%])-$CO_2$-Air-$N_2$] Volume percentage of aqueous NaOH solution used was 20[%] and $N_2$flow rate was 2.5[$\ell$/min] for bubbling aqueous NaOH solution Ammonia gas(14.81[%]) balanced by argon was diluted by air. NH$_3$ molecular ratios(MR) based on [NH$_3$] and [NO+SO$_2$] were 1, 1.5 and 2.5 The vapour of aqueous NaOH solution and NH$_3$was introduced to the main simulated combustion flue gas duct through injection systems which were located at downstream of corona discharge reactor. NOx(NO+NO$_2$) removal rate by injecting the vapour of aqueous NaOH solution was much better than that by injecting NH$_3$however SO$_2$removal rate by injecting NH$_3$was much better than that by injecting the vapour of aqueous NaOH SO$_2$removal rate slightly increased with increasing applied voltage. When the vapour of aqueous NaOH solution and NH$_3$were simultaneously injection NOx and SO$_2$ removal rate were significantly increased.

• 신재생에너지
• /
• 제6권4호
• /
• pp.6-14
• /
• 2010

Pretreatment of cellulosic biomass is necessary before enzymatic saccharification and fermentation. Extrusion is a well established process in food industries and it can be used as a physicochemical treatment method for cellulosic biomass. Aqueous ammonia soaking treatment at mild temperatures ranging from 60 to $80^{\circ}C$ for longer reaction times has been used to preserve most of the cellulose and hemicellulose in the biomass. The objective of this study was to evaluate the effect of extrusion treatment on aqueous ammonia soaking method. Extrusion was performed with miscanthus sample conditioned to 2mm of particle size and 20% of moisture content at $200^{\circ}C$ of barrel temperature and 175rpm of screw speed. And then aqueous ammonia soaking was performed with 15%(w/w) ammonia solution at $60^{\circ}C$ for 1, 2, 4, 8, 12 hours on the extruded and raw miscanthus samples respectively. In the combined extrusion-soaking treatment, most compositions removal occurred within 1~2 hours and on a basis of 1 hour soaking treatment values, cellulose was recovered about 85% and other compositions, including hemicellulose, are removed about 50% from extruded miscanthus sample. The combined extrusion-soaking treated and soaking only treated samples were subjected to enzymatic hydrolysis using cellulase and ${\beta}$-glucosidase. The enzymatic digestibility value of combined extrusion-2 hours soaking treated sample was comparable to 12 hours soaking only treated sample. It means that extrusion treatment can shorten the conventional long reaction time of aqueous ammonia soaking. The findings suggest that the combination of extrusion and soaking is a promising pretreatment method to solve both problems for no lignin removal of extrusion and long reaction time of aqueous ammonia soaking.

• 한국재료학회지
• /
• 제10권6호
• /
• pp.445-449
• /
• 2000

가압 경수형 원자로 (pressurized light water reactor) 냉각재 계통 내의 주된 분식 생성물로 알려져 있는 nickel ferrite의 거동에 대해 고찰하기 위해 모의 nickel ferrite($Ni_{0.75}Fe_{2.25}O_4$)를 공침법으로 제조하였다. 수용액-pH-조절로는 am-monia 또는 potassium carbonate를, 공침물-세척제는 ammonia 수용액이나 potassium carbonate 수용액 또는 2차 증류수를 사용하였다. Nickel ferrite의 생성 및 수용액-pH-조절제와 공치물-세척제가 최종 생성물의 Ni-Fe 몰 비에 따른 수율 및 특성에 미치는 영향은 EDX, XPS, XRD 및 SEM으로 고찰하였다. 반응 전.후 Ni/Fe 몰 비에 따른 수율은, pH를 potassium carbon-ate로 조절한 후 2차 증류수로 공침물을 세척한 경우가 0.994로 가장 높이 나왔으며, pH-조절제로 potassium carbonate를 사용한 경우가 ammonia를 사용한 경우에 비해 높은 수율을 나타냈다. 이러한 차이는 공침 시에 수용액 내에서 ammonia가 보여주는 상대적으로 큰 $Na_{2+}{\leftarrow}NH_3$ 착화 효과와 더불어 공침물-세척제의 pH에 기인하는 것으로 해석하였다.

• Bulletin of the Korean Chemical Society
• /
• 제6권6호
• /
• pp.329-333
• /
• 1985

A procedure for the preparation of peptizable pseudoboehmite has been described in detail based upon a process of neutralization of an aqueous aluminum sulfate or chloride solution with aqueous ammonia. In order to obtain peptizable pseudoboehmite products, carefully controlled conditions were required in the whole processes of neutralization, aging, washing, and drying. The optimum conditions experimentally found are the following. The aluminum salt solution is neutralized with aqueous ammonia until the final pH of the solution reaches 10.0 to 10.8 or 9.0 to 9.3 for the sulfate of chloride, respectively. The alumina gel formed is subjected to aging at $80^{\circ}C for about 3 hours and washed with water more than 5 times to reduce the residual sulfate or chloride ion in the final products to less than 4%. The pseudoboehmite gel thus obtained should be dried oven at 80 to $100^{\circ}C for a few to several hours depending on the selected temperatures.

• 설비공학논문집
• /
• 제14권10호
• /
• pp.817-824
• /
• 2002

A diffusion absorption refrigerator is a heat-generated refrigeration system. It uses a three-component working fluid consisting of the refrigerant (ammonia), the absorbent (water) and the auxiliary gas (typically hydrogen). This system has no moving parts and the associated noise and vibration. In this study, the operating characteristics of diffusion absorption refrigerator are investigated through cycle modeling and simulation. System parameters considered in this study are the charged concentration of ammonia aqueous solution, the concentration difference between absorber inlet and outlet and the system pressure determined by the amount of auxiliary gas charged. It was found that there exists a critical value of concentration difference that maximizes the refrigerating capacity. And the lower the system pressure, the higher the refrigerating capacity.