논문 : 급속교반조건에서 Alum 응집제의 가수분해종 분포특성과 유기물특성변화

송유경 ( Yu Kyung Song ),정철우 ( Chul Woo Jung ),손희종 ( Hee Jong Son ),손인식 ( In Shik Sohn ) 대한상하수도학회 2006 상하수도학회지 Vol.20 No.4

The overall objective of this research was to find out the interrelation of coagulant and organic matter during rapid mixing process and to identify the change of organic matter by mixing condition and to evaluate the effect of coagulation pH. During the coagulation, substantial changes in dissolved organics must be occurred by coagulation due to the simultaneous formation of microflocs and NOM precipitates. Increase in the organic removal efficiency should be mainly caused by the removal of microflocs formed during coagulant injection. That is, during the mixing period, substantial amount of dissolved organics were transformed into microflocs due to the simultaneous formation of microflocs and NOM precipitates. The results also showed that 40 to 80% of dissolved organic matter was converted into particulate material after rapid mixing process of coagulation. During the rapid mixing period, for purewater, formation of dissolved Al(Ⅲ) (monomer and polymer) constant by rapid mixing condition, but for raw water, the species of Al hydrolysis showed different result. During the rapid mixing period, for high coagulant dose, Al-ferron reaction increases rapidly. At A/D(Adsorption and Destabilization) and sweep condition, both Al(OH)3(s) and dissolved Al(Ⅲ) (monomer and polymer) exist, concurrent reactions by both mechanism appear to cause simultaneous precipitation.

Development of rapid mixing fuel nozzle for premixed combustion

Katsuki Masashi,정진도,김장우,황승민,김승모,안철주 대한기계학회 2009 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.23 No.3

Combustion in high-preheat and low oxygen concentration atmosphere is one of the attractive measures to reduce nitric oxide emission as well as greenhouse gases from combustion devices, and it is expected to be a key technology for the industrial applications in heating devices and furnaces. Before proceeding to the practical applications, we need to elucidate combustion characteristics of non-premixed and premixed flames in high-preheat and low oxygen concentration conditions from scientific point of view. For the purpose, we have developed a special mixing nozzle to create a homogeneous mixture of fuel and air by rapid mixing, and applied this rapidmixing nozzle to a Bunsen-type burner to observe combustion characteristics of the rapid-mixture. As a result, the combustion of rapid-mixture exhibited the same flame structure and combustion characteristics as the perfectly prepared premixed flame, even though the mixing time of the rapid-mixing nozzle was extremely short as a few milliseconds. Therefore, the rapid-mixing nozzle in this paper can be used to create preheated premixed flames as far as the mixing time is shorter than the ignition delay time of the fuel.

급속혼화조건에서 Al(Ⅲ) 가수분해종의 분포특성

정철우,손정기,손인식,강임석 대한상하수도학회 2004 상하수도학회지 Vol.18 No.2

The overall objective of this research was to find out the role of rapid mixing conditions in the species of hydrolyzed Al(Ⅲ) formed by different Al(Ⅲ) coagulants. When an Al(Ⅲ) salt is added to water, monomers, polymers, or solid precipitates may form. Different Al(Ⅲ) coagulants (alum and PACI) show to have different Al species distribution over a rapid mixing condition. During the rapid mixing period, for alum, formation of dissolved Al(Ⅲ) (monomer and polymer) increases, but for PACI, precipitates of Al(OH)_(3(s)) increases rapidly. Also, for alum, higher mixing speed favoured Al(Ⅲ) polymers formation over precipitates of Al(OH)_(3(s)) but for PACI, higher mixing speed formed more precipitates of Al(OH)_(3(s)). At A/D and sweep condition, both Al(OH)_(3(s)) and dissolved Al(Ⅲ) (monomer and polymer) exist, concurrent reactions by both mechanism appear to cause simultaneous precipitation.

현장발생토를 활용한 토류구조물 뒷채움용 유동화처리토의 최적 배합비 산정과 재료거동에 관한 실험적 연구

조대호(Cho Dae Ho),한상재(Han Sang Jae),김종윤(Kim Jong Yun),김수삼(Kim Soo Sam) 대한토목학회 2007 대한토목학회논문집 C Vol.27 No.3

재굴착이 용이하고 고유동성 재료로 알려져 있는 저강도 유동성 채움재(CLSM)는 일반적으로 트렌치를 굴착한후 관하부의 뒤채움재로 주로 시용되어 왔으며, 현재는 대규모 지하 구조물의 뒤채움재, 건축 구조물의 뒤채움재, 노면하부 공동의 뒤채움재 등 다양한 용도로 사용되고 있다. 본 연구에서는 현장발생토를 이용한 CLSM의 한 종류인 급결성 유동화처리토의 특징을 파악하기 위해 현장에서 채취한 시료를 통일분류법의 5가지(SW, SM, SC, ML, CL)시료에 대하여, 각각 유동성과 블리딩실험을 실시하였다. 이를 바탕으로 시간에 따른 공시체의 물리 거동을 분석하여 영향인자별 강도 발현특성 및 최적의 배합비를 도출하였다. Controlled low-strength material (CLSM) which is well known as specific material having high flowable and easily re-excavated, is commonly used as a backfill in utility trenches and other applications. In this study, experimental progresses such as the flow test, bleeding test and shear strength test were conducted to understand the behavior characteristics of the rapid-setting flowable material which a kind of CLSM for 5 kinds of soil taken from field and separated according to unified soil classification system (USCS). Based on these tests, the physical behavior of specimen was analyzed so that the strength characteristics and optimum mixing ratio according to effective factors were evaluated.

문화재 보존처리에 사용되는 에폭시수지의 사용현황과 배합비율에 따른 물성 변화 연구

이은지,장성윤 한국문화재보존과학회 2016 보존과학회지 Vol.32 No.2

2액형 에폭시 수지는 문화재 보존처리에 매우 광범위하게 사용되고 있으나 사용 시 주제와 경화제의 배합비율에 따라 경화특성, 기계적 강도, 화학 구조 등이 달라질 수 있고 대상 문화재의 안정성에 영향을 미칠 수 있다. 설문조사 결과, 보존처리 실무자들은 소량의 에폭시수지를 눈대중으로 혼합하거나 가사시간을 줄이기 위해 인위적으로 경화제를 과량 첨가하는 경우가 있는 것으로 조사되었다. 이 연구에서는 속경화형 2종과 일반경화형 2종의 에폭시수지를 대상으로 주제에 대한 경화제의 비율을 0.25~4배로 설정하여 각 경우의 경화특성, 기계적 강도, 화학 작용기를 분석하였다. 그 결과 속경화형 에폭시수지는 경화제가 0.5~2배일 때 높은 반응열과 함께 경화반응이 빠르게 나타났으며, 경화제 비율이 제조사에서 공시된 정비율보다 적을 때 더 높은 기계적 강도가 나타났고 에폭시의 가교결합도 활발히 일어난 것으로 관찰되었다. 일반경화형 에폭시수지는 대부분 경화반응열이 낮고 느린 반응속도로 경화가 진행되며, 경화제가 정비율 이하에서 가장 높은 기계적 강도를 나타냈다. 그러나 경화제 비율이 2배 이상 일 때는 경화속도가 매우 느려지고 접착강도도 낮아지는 것으로 나타났다. 따라서 배합비가 정비율 이하에서는 비교적 빠른 반응속도와 유사한 기계적 강도를 나타내는 반면 정비율 이상에서는 물성이 급격하게 저하되므로 구현하고자 하는 성능에 영향을 미칠 수 있을 것으로 판단된다. Two-component epoxy resin is widely used in the cultural heritage restoration field. However according to mixing ratio of resin and hardener, curing property, mechanical strength and chemical structure differ which have possibility to effect the stability of cultural heritage. Result of questionnaire survey shows hands-on workers in the conservation field tend to mix the epoxy resin with his or her eye measurement when the using amount is small or mix additional hardener to shorten the pot life of epoxy resin. This research aims to analyze the curing property, mechanical strength and chemical structure of rapid curing type epoxy resin and medium curing type one depending on relative ratio of 0.25~4 of hardener to resin. When the amount of hardener was 0.5~2 times more than the resin, exothermic heat and curing speed were both increased. In case of included hardener to resin was lower than official ratio, mechanical strength (tensile shear strength, tensile strength and compressive strength) became higher along with active cross-linking bonding of the epoxy resin. Medium curing type epoxy relatively had lower exothermic heat and slower reaction during curing process. It was observed to be put to definite point of mechanical strength under lower content of hardener than official ratio. While, hardener ratio more than twice the resin slowed down the curing greatly and lowered the adhesion strength also. In conclusion, under the lower mixing rate of hardener than official ratio would show relatively fast reaction with similar mechanical strength. Over the official ratio on the other hand, material property drops rapidly. Accordingly, mixing ratio of epoxy resin is expected to be influential to the stability of cultural heritage.

Effects of hydrodynamics and coagulant doses on particle aggregation during a rapid mixing

Sang-Min Park,Tae-Young Heo,Jun-Gyu Park,Hang-Bae Jun 대한환경공학회 2016 Environmental Engineering Research Vol.21 No.4

The effects of hydrodynamics and alum dose on particle growth were investigated by monitoring particle counts in a rapid mixing process. Experiments were performed to measure the particle growth and breakup under various conditions. The rapid mixing scheme consisted of the following operating parameters: Velocity gradient (G) (200-300 s<SUP>-1</SUP>), alum dose (10-50 mg/L) and mixing time (30-180 s). The Poisson regression model was applied to assess the effects of the doses and velocity gradient with mixing time. The mechanism for the growth and breakup of particles was elucidated. An increase in alum dose was found to accelerate the particle count reduction. The particle count at a G value of 200 s<SUP>-1</SUP> decreased more rapidly than those at 300 s<SUP>-1</SUP>. The growth and breakup of larger particles were more clearly observed at higher alum doses. Variations of particles due to aggregation and breakup of micro-flocs in rapid mixing step were interactively affected by G, mixing time and alum dose. Micro-flocculation played an important role in a rapid mixing process.

응집공정에 적합한 In-Line 정적혼화기를 이용한 혼화공정의 개선

정철우,강민수,최시환,정수일,손인식,강임석 대한상하수도학회 2003 상하수도학회지 Vol.17 No.3

The rapid mixing process for coagulation is a critical component in a water treatment plant. However, at the present time a detailed understanding of the rapid mixing by in-line mixer or generally accepted criteria for the design of in-line static mixer are not available. The aim of this work is therefore to improve the understanding of how the in-line static mixer works and how to better utilize it in coagulation process in water treatment. To investigate the performance of static mixer, coagulation experiments were conducted to compare the static mixer to the traditional backmixer under several coagulation conditions. Experiments were also performed to compare the coagulation efficiency of different mixing type of static mixer which were made using different flow rates and the number of elements equipped in a pipe. The static mixer performed better than the backmixer for all coagulation and mixing conditions tested. Especially, the static mixer was very effective in the surface charge neutralization, as showing higher reduction of negative charge with increasing mixing intensity. However, little difference was observed in the performance of the static mixer equipped with 2, 3, and 5 elements. Also, in a series of bench-scale studies of rapid mixing, the in-line static mixer performed better than the traditional backmixer for both adsorption and charge neutralization (A/N) mechanism and sweep coagulation mechanisms. Especially, the static mixer was more efficient at producing A/N mechanism conditions as a result of its fast and uniform dispersion of the coagulant.

가수분해 산물 분포를 이용한 급속혼화강도가 화학적 인 제거 효율에 미치는 영향의 규명

김승현,윤동수,문병현 대한상하수도학회 2011 상하수도학회지 Vol.25 No.3

Mechanism of rapid mixing effect on chemical phosphorus removal is evaluated in this study. Assuming that chemical phosphorus removalis unaffected by mixing time, only rapid mixing intensity is evaluated. In order to find out the mechanism, it is hypothesized that rapid mixing affects the Al hydrolysis speciation, and that formation of more monomeric species (Ala) results in better removal of phosphorus. According to a ferron assay, more Ala formed at higher mixing intensity than at lower intensity. Subsequent experiments revealed that better phosphorus removal was obtained at higher intensity than at lower intensity, in terms of the molar ratio of Aladded/Premoved. The proposed hypothesis was proved in this study. Chemical phosphorus removal is affected by rapid mixing intensity due to its effect on the Al hydrolysis speciation.

급속교반공정에서 응집조건이 입자성장에 미치는 영향

전항배 ( Hang Bae Jun ),전동걸 ( Dong Jie Tian ) 충북대학교 산업과학기술연구소 2015 산업과학기술연구 논문집 Vol.29 No.1

Micro-floc growth at a various rapid mixing condition was investigated with synthetic water sample containing kaolin particles by standard jar tests. The growth and breakup of the micro-floc occurred during the rapid mixing process, and the rapid mixing condition with high intensity and short mixing time was unfavorable for the micro-floc formation. The major factor for micro-floc formation was velocity gradient, G product mixing time (G·t) values. Breakup of the micro-floc happened at G·t values above 30,000. At G·t values below 30,000, most favorable G values were below 300 sec-1. At G values above 400 sec-1 the micro-floc did not grow any more but it broke up at an extended mixing time. Ratio of Group 1 particles (below 8 ㎛) increased at higher alum dose, while those of Group 2 and 3 decreased. The optimum rapid mixing contions for micro-floc (larger than 8 ㎛) formation was at G values below 300 sec-1, t values below 150 sec, at G·t values below 30,000 and alum dose below 20 mg-alum/L, respectively.

Evaluation of mixing conditions using an on-line monitoring technique

Yong Doo Lee,Sang Goo Kim,Keun Joo Choi,Pyung Jong Yu,김승현 한국화학공학회 2008 Korean Journal of Chemical Engineering Vol.25 No.1

Effects of mixing conditions on flocculation were investigated by using a photometric ispersion analyzer (PDA) as an on-line monitoring technique in this study. Both river water and synthetic waters of humic acid (HA) and kaolin solutions were used and polyaluminum chloride (PACl) were used as a coagulant in this study. A clear relationship between F-index and residual turbidity was observed. Residual turbidity was low at high F-index. The mixing effects were also found closely related to the floc formation. When the floc formation was governed by a combination of charge neutralization and sweep floc, rapid mixing was important, but it was not important when the floc formation was governed by the sweep floc mechanism. The coagulant dosage governed the floc size and strength in the sweep floc region. The higher the coagulant dosage was, the larger but the weaker the floc was. Rapid mixing effects were different, depending on raw water characteristics. Fast and large floc formation was observed in flocculation of the kaolin solution, compared to that of the HA solution. Small HA would be mostly adsorbed onto the hydroxide precipitate after the precipitate formed. The adsorption could retard further floc growth. The resulting floc was small, and the floc formation was slow. However, kaolin helped flocculation by bridging the hydroxide precipitates, leading to fast and large floc formation. Temperature affected the flocculation kinetics as well as the floc size. A large floc formed at high temperature. The flocculation kinetics became fast with increasing temperature.