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모델 예측 제어 기법을 이용한 상압 증류공정의 제어

Control of Atmospheric Distillation Unit Using Model Predictive Control Technique

서정원 김경현 김석준 오민^1† 이태희

Jung Won Seo Kyung Hyun Kim Suk Joon Kim Min Oh^1† Tae Hee Lee

연세대학교 화학공학과, 서울 120-749 ¹한밭대학교 화학공학과, 서울 120-749

Department of Chemical Engineering, Yonsei University, Seoul 120-749, Korea ¹Department of Chemical Engineering, Hanbat National University, Daejeon 300-172, Korea

minoh@hanbat.ac.kr

HWAHAK KONGHAK, April 2002, 40(2), 152-158(7), NONE

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Abstract

에너지 소비가 큰 원유 증류공정은 운전비용과 직접 관련이 되는 최적 운전조건의 유지를 위한 고급제어전략이 필요하다. 본 연구에서는 기존의 PID 제어기를 대체할 새로운 제어 시스템을 도입하는 데에 있어서 타당성 검토와 이를 구현하였을 경우에 예상되는 공정 동특성을 예측하기 위하여, 대표적인 고급제어이며 최근에 널리 쓰이고 있는 모델예측제어 알고리듬을 65,000 BPSD 규모의 상압 증류공정에 적용하여 제어성능을 비례 적분 미분 제어의 제어성능과 비교하였다. 정상상태 및 동적 모사를 통하여 공정의 모델을 구하였다. 원유 증류공정의 생성물인 중질 나프타, 등유, 경질 가스유, 중질 가스유의 유량을 제어변수로 정하여 각 제어변수에 대하여 모델 예측 제어 제어구조의 제어성능을 비례 적분 미분 제어구조의 제어성능과 비교해 본 결과 모델 예측 제어 제어구조의 제어응답이 더욱 안정적이고 설정값과의 잔류편차도 없음을 알 수 있었다. 또한 모델 예측 제어 제어구조는 설정값추적 문제의 경우에도 안정적인 응답을 보였으며, 조율 매개변수의 변화에 따른 응답의 변화가 거의 없음을 알 수 있었다.

An atmospheric distillation unit is an energy intensive process, which requires an advanced controller to maintain the optimal operating conditions. To investigate the feasibility for the replacement of conventional controllers, PIDs, with advanced controllers and to estimate the dynamic responses of the process, the simulation of the model predictive control (MPC) structures for the 65,000 BPSD atmospheric distillation unit was attempted. The performances of the MPC were compared with those of proportional-integral-derivative control. The controlled variables were the flow rates of products such as heavy naphtha, kerosene, light gas oil and heavy gas oil. The transfer functions were calculated from the dynamic simulation based the steadystate simulation of the process. In comparison with the conventional controller, we obtained more stable response from the MPC algorithm for the control of the atmospheric distillation unit. It was also shown that the MPC had very small offsets for the both of servo and the regulator problems.

Keywords

MPC CDU Simulation DMC

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