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Control of pH Neutralization Proess Using Simulation Based Dynamic Programming
양대륙,이광순,김동규 한국화학공학회 2004 Korean Journal of Chemical Engineering Vol.21 No.5
The pH neutralization process has long been taken as a representative benchmark problem of nonlinear chemical process control due to its nonlinearity and time-varying nature. For general nonlinear processes, it is difficult to control with a linear model-based control method so nonlinear controls must be considered. Among the numerous approaches suggested, the most rigorous approach is the dynamic optimization. However, as the size of the problem grows, the dynamic programming approach suffers from the curse of dimensionality. In order to avoid this problem, the Neuro-Dynamic Programming (NDP) approach was proposed by Bertsekas and Tsitsiklis [1996]. The NDP approach is to utilize all the data collected to generate an approximation of optimal cost-to-go function which was used to find the optimal input movement in real time control. The approximation could be any type of function such as polynomials, neural networks, etc. In this study, an algorithm using NDP approach was applied to a pH neutralization process to investigate the feasibility of the NDP algorithm and to deepen the understanding of the basic characteristics of this algorithm. As the approximator, the neural network which requires training and the k-nearest neighbor method which requires querying instead of training are investigated. The approximator has to use data from the optimal control strategy. If the optimal control strategy is not readily available, a suboptimal control strategy can be used instead. However, the laborious Bellman iterations are necessary in this case. For pH neutralization process it is rather easy to devise an optimal control strategy. Thus, we used an optimal control strategy and did not perform the Bellman iteration. Also, the effects of constraints on control moves are studied. From the simulations, the NDP method outperforms the conventional PID control.
P-40 : The Simulation and Control of the Reactive Distillation Process for DMC Production
장용희,양대륙,안병성 한국화학공학회 2007 화학공학의이론과응용 Vol.10 No.2
Reactive distillation (RD) is a combination process where both separation and reaction are considered simultaneously in a single vessel. The RD system has been used for a long time as a useful process and recently the importance of the RD is enlarged more and more. To make the most of the characteristic of RD system, we must decide the best operating condition under which the process shows the most effective productivity and should decide the best control algorithm which satisfies an optimal operating condition. In this study, RD is used for DMC production process and the transesterification is performed inside of column to produce DMC. This process use homogeneous catalyst and the azeotrope exists between the reactant and product. Owing to azeotrope, we should use two distillation columns. For this DMC production process, we can suggest two configurations (EC and methanol excess process). From the comparison of steady state simulation results, it showed the better performance to use the methanol excess process configuration than EC excess process. Then, the dynamic simulation was performed to be based on the steady state simulation results and the optimal control system was designed.
1,1,1,2,3,3,3-Heptafluoropropane(HFC-227ea)과 propane(HC-290)의 2성분계 기-액 평형 측정
진현상,양대륙,이병권,유기풍,임종성 한국화학공학회 2007 화학공학의이론과응용 Vol.10 No.2
혼합 냉매를 사용할 경우, 기-액 상평형 데이터는 냉매의 성능 평가나 냉동시스템에 적합한 조성의 결정을 위해 사용된다. 그리고 비인화성의 HFC 냉매와 프로판을 혼합하여 사용할 경우 지구 온난화 정도나 인화성을 낮출 가능성이 있다. 본 연구에서는 HFC-227ea와 propane의 이성분계 상평형 데이터를 얻기 위한 실험을 실행하였으며, 온도는 283.15, 293.15, 303.15, 313.15K에서 행하였다. 상평형 실험 장치로는 circulation type의 장치를 사용하였다. 실험데이터는 MF-NLF(multi-fluid nonrandom lattice fluid) 상태방정식을 이용하여 상관관계를 알아보았다. MF-NLF 상태방정식을 이용하여 얻은 데이터는 실험 데이터와 만족할 만한 일치를 볼수 있었다. 그리고 혼합냉매 사용에 중요한 이점으로 작용하는 특성인 공비점이 실험을 실행한 모든 온도에서 형성하는 것을 확인하였다.
신동균,양대륙 한국화학공학회 2007 화학공학의이론과응용 Vol.10 No.2
Simultaneous saccharification and fermentation (SSF) process consists of the enzymatic saccharification and fermentation simultaneously. This study combined saccharification based on modified Michaelis-Menten kinetics and enzyme inhibition kinetics with fermentation based on the Monod equation and cybernetic model. The cybernetic modeling using Brettanomyces custersii identified as a glucose- and cellobiose-fermenting yeast was suitable for describing the sequential growth on multiple substrates. The proposed model improved the previous SSF kinetic model, and testified the validity of the cybernetic model for correlating with previous experimental results.