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마이크로채널 반응기를 이용한 강화된 저온 피셔-트롭쉬 합성반응의 전산유체역학적 해석
Krishnadash S. Kshetrimayum,나종걸(Jonggeol Na),박성호(Seongho Park),정익환(Ikhwan Jung),이용규(Yongkyu Lee),한종훈(Chonghun Han) 한국가스학회 2017 한국가스학회지 Vol.21 No.4
피셔-트롭쉬 합성반응은 CO와 H2의 혼합가스로 이루어진 합성가스를 부가가치가 높은 탄화수소 제품으로 변환시킨다. 본 논문에서는 저온 피셔-트롭쉬 합성반응과 단일, 다중 마이크로채널 반응기에 패킹시킨 촉매를 기반으로 강화된 반응조건의 열전달을 고려하여 전산유체역학 기반의 시뮬레이션을 진행하고 분석하였다. 단일채널모델을 통하여 CO 전환률이 ~65% 이상, C<SUB>5+</SUB> 선택도가 ~74% 이상을 달성하면서도 Co 기반의 super-active 촉매를 통해 GHSV를 30000 hr<SUP>-1</SUP>을 달성할 수 있음을 보였다. 다중 마이크로채널 반응기모델에서는 열전달 시뮬레이션을 동시에 해석하여, 3가지의 다른 반응기구조에 대해서, 직교류 wall boiling 냉매를 사용시 △T<SUB>max </SUB>가 23 K였으며 평행유동 subcooled 냉매와 평행유동 wall boiling 냉매의 경우 각각 15 K와 13 K의 △T <SUB>max</SUB> 를 보였다. 반응기 전체적으로 498 - 521 K에서 온도제어가 가능했으며 계산된 사슬성장 가능성은 저온 피셔-트롭쉬 합성에 적합한 것으로 보인다. Fischer-Tropsch synthesis reaction converts syngas (mixture of CO and H2) to valuable hydrocarbon products. Simulation of low temperature Fischer -Tropsch Synthesis reaction and heat transfer at intensified process condition using catalyst filled single and multichannel microchannel reactor is considered. Single channel model simulation indicated potential for process intensification (higher GHSV of 30000 hr<SUP>-1</SUP> in presence of theoretical Cobalt based super-active catalyst) while still achieving CO conversion greater than ~65% and C<SUB>5+</SUB> selectivity greater than ~74%. Conjugate heat transfer simulation with multichannel reactor block models considering three different combinations of reactor configuration and coolant type predicted ΔTmax equal to 23 K for cross-flow configuration with wall boiling coolant, 15 K for co-current flow configuration with subcooled coolant, and 13 K for co-current flow configuration with wall boiling coolant. In the range of temperature maintained (498 - 521 K), chain growth probability calculated is desirable for low-temperature Fisher-Tropsch Synthesis.
전산유체역학을 이용한 이산화탄소 광물 탄산화 반응기 분석: 용액 내 고체 반응물 교반 향상을 위한 내부 구조 설계
박성언 ( Seongeon Park ),나종걸 ( Jonggeol Na ),김민준 ( Minjun Kim ),안진주 ( Jinjoo An ),이채희 ( Chaehee Lee ),한종훈 ( Chonghun Han ) 한국화학공학회 2016 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.54 No.5
Aqueous mineral carbonation process, in which CO2 is captured through the reaction with aqueous calcium oxide (CaO) solution, is one of CCU technology enabling the stable sequestration of CO2 as well as economic value creation from its products. In order to enhance the carbon capture efficiency, it is required to maximize the dissolution rate of solid reactants, CaO. For this purpose, the proper design of a reactor, which can achieve the uniform distribution of solid reactants throughout the whole reactor, is essential. In this paper, the effect of internal reactor designs on the solid dispersion quality is studied by using CFD (computational fluid dynamics) techniques for the pilot-scale reactor which can handle 40 ton of CO2 per day. Various combination cases consisting of different internal design variables, such as types, numbers, diameters, clearances and speed of impellers and length and width of baffles are analyzed for the stirred tank reactor with a fixed tank geometry. By conducting sensitivity analysis, we could distinguish critical variables and their impacts on solid distribution. At the same time, the reactor design which can produce solid distribution profile with a standard deviation value of 0.001 is proposed.
전산유체역학을 이용한 Fischer-Tropsch 마이크로채널 반응기 반응채널구조에 따른 열적 효과 분석
이용규 ( Yongkyu Lee ),정익환 ( Ikhwan Jung ),나종걸 ( Jonggeol Na ),박성호 ( Seongho Park ),( Krishnadash S. Kshetrimayum ),한종훈 ( Chonghun Han ) 한국화학공학회 2015 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.53 No.6
In this study, FT reaction in a microchannel was simulated using computational fluid dynamics(CFD), and sensitivity analyses conducted to see effects of channel geometry variables, namely, process channel width, height, gap between process channel and cooling channel, and gap between process channels on the channel temperature profile. Microchannel reactor considered in the study is composed of five reaction channels with height and width ranging from 0.5 mm to 5.0 mm. Cooling surfaces is assumed to be in isothermal condition to account for the heat exchange between the surface and process channels. A gas mixture of H2 and CO(H2/CO molar ratio = 2) is used as a reactant and operating conditions are the following: GHSV(gas hourly space velocity) = 10000 h-1, pressure = 20 bar, and temperature = 483 K. From the simulation study, it was confirmed that heat removal in an FT microchannel reactor is affected channel geometry variables. Of the channel geometry variables considered, channel height and width have significant effect on the channel temperature profile. However, gap between cooling surface and process channel, and gap between process channels have little effect. Maximum temperature in the reaction channel was found to be proportional to channel height, and not affected by the width over a particular channel width size. Therefore, microchannels with smaller channel height(about less than 2 mm) and bigger channel width (about more than 4 mm), can be attractive design for better heat removal and higher production.
고정층 Fischer-Tropsch 반응기의 액상 왁스 정체 현상 모델링
박찬샘(Chansaem Park),정익환(Ikhwan Jung),박성호(Seongho Park),나종걸(Jonggeol Na),Krishnadash Kshetrimayum,한종훈(Chonghun Han),이종열(Jong Yeol Lee),정종태(Jongtae Jung) 한국가스학회 2014 한국가스학회지 Vol.18 No.4
Fischer-Tropsch 합성은 주로 긴 carbon 사슬을 가지고 있는 높은 점도의 왁스를 product로 생산한다. 촉매 고정층 반응기를 이용하여 Fischer-Tropsch 합성을 수행할 경우, 왁스는 촉매입자의 표면에서 생산되어 촉매입자 표면에 흡착되어 있다. 이런 왁스의 hold-up 현상이 반응기 전체의 압력강하는 증가시키고 내부 흐름을 막는 문제를 일으킨다. 따라서 반응기 내부에 왁스가 hold-up되는 현상에 대한 모델링을 통해 왁스 hold-up 현상을 최소화 할 수 있는 반응기 및 촉매 입자의 크기를 결정하는 설계 과정이 필요하다. 본 연구에서는 왁스가 hold-up된 촉매 입자와 기체 흐름 사이의 대류 물질 전달 실험 모델을 이용하여 반응기 구조 및 운전 조건을 고려할 수 있는 반응기 내부 왁스 hold-up 모델을 개발하였다. 개발된 모델은 실험 데이터를 제공한 Knochen의 연구 결과와 비교하여 모델의 우수성을 검증하였다. 이 모델을 이용하여 반응기의 길이와 단면이 반응기 내부 왁스 hold-up 현상에 어떻게 영향을 미칠 수 있는지 분석해 보았다. Fischer-Tropsch synthesis mainly produces a wax which is a viscous liquid for long carbon chain. When a catalytic fixed-bed reactor is used for Fischer-Tropsch synthesis, the wax generated on a catalyst surface can keep adsorbing on the catalyst surface. This liquid hold-up causes significant pressure drop and clogging problems through the reactor. Thus, the model for liquid hold-up is required to design the size of reactor and catalyst particles. In this study, the liquid hold-up model considering structural and operational conditions was proposed based on empirical equations for convective mass transfer between the syngas flow and the wax-adsorbed catalyst. The developed model was validated by comparing with the experimental data from Knochen’s work (2010). The influence of reactor length and coross section on the wax hold-up in reactor were analyzed and the optimal reactor size were proposed.