Pinch Technology를 이용한 벤젠-톨루엔-자일렌 분리공정 에너지 최적화에 관한 연구

Abstract

증류공정은 혼합물 분리에 활용되는 중요한 공정이나, 그 특성상 에너지 소모가 많으면서도 상대적으로 에너지 효율이 낮은 공정이다. 이러한 증류공정의 비효율 개선을 위해 실시되었던 여러 선행연구의 연장선상에서, 본 연구에서는 BTX 분리공정을 대상으로 Pinch Technology를 이용하여 에너지 최적화 및 경제성 평가를 수행하였다. BTX 분리공정의 프로세스 흐름간 열교환 구성 가능여부를 Pinch Technology 기반 모사기인 Aspen Energy Analyzer®를 활용하여 판정 및 열교환 네트워크 case를 도출하였다. 구성된 열교환 네트워크에 따라 case별 프로세스를 구현, 총 10개 scenario-case에 대한 Aspen HYSYS® 활용 공정모사를 실시하였다. 주요 설비(증류탑, 열교환기, 펌프, 저장기, 수증기 ejector)의 sizing 및 가격산정을 실시, 총장치비를 기준으로 총투자비를 산정, 주요 기기의 utility소모량을 산정하여 연간운전비를 계산하였고, 총투자비+20년간 운전비를 기준으로 각 scenario-case에 대한 경제성을 평가하였다. 공정상 벤젠 증류탑의 후단에 위치한 톨루엔 증류탑의 운전압을 2kg/cm2g로 가압, 톨루엔 증류탑 탑상의 온도를 153℃까지 높이고 이 고온 흐름을 벤젠 증류탑의 재비기의 열원으로 사용하는 case인 ‘Scenario#3-Case#1’이 가장 경제성 우수한 것으로 최종 선정되었고, 같은 조건에서 톨루엔 증류탑 재비기에 사용된 열원을 벤젠 증류탑 원료와 한번 더 열교환하여 원료 예열기를 대체하는 ‘Scenario#3-Case#2’도 경쟁력 있는 차선 case로 선정되었다. 가장 경제성이 우수한 case로 선정된 ‘Scenario#3-Case#1’의 경우 본 연구의 비교검토 기본 case(프로세스 흐름간 열교환이 없이 유틸리티로만 열교환된 case)인 ‘Scenario#1-Base Case’ 대비 총투자비는 약42% 크지만, 연간운전비는 약20% 절감, 총투자비와 20년간 운전비의 합은 약19% 절감되는 것으로 나타났다. |The distillation process is world-widely utilized in the separation of mixtures. However, due to the intrinsic thermodynamic inefficiency in this process, many studies have been performed to improve distillation’s inefficiency. In connection with the prior studies, the energy optimization was performed in BTX fractionation process utilizing Pinch Technology. Heat exchanging networks, the heat exchanging matches between process-process flows, have been developed using Aspen Energy Analyzer® simulator in the technical application of Pinch Technology. Based on the developed heat exchanging networks, the feasible process configurations were simulated by Aspen HYSYS® process simulator. Total 10 scenario-cases were derived as the energy optimization cases. Sizing and cost estimation for major equipments such as columns, heat exchangers, pumps, vessels and steam ejector were performed based on the Aspen HYSYS® process simulation results. Total investment cost(TIC) was estimated from the calculated total equipment cost(TEC). Annual operation cost(AOC) was calculated based on the utility consumption of cooling water, MP steam and electricity. The economic evaluation was performed in terms of the total investment cost(TIC) plus 20 years’ operation cost. ‘Scenario#3-Case#1’(toluene column pressurized operation up to 2kg/cm2g with the hot process flow of 153℃ in toluene column top sharing the heat duty of benzene column reboiler) was the most economic case among the study cases. ‘Scenario#3-Case#2’(same process condition with ‘Scenario#3-Case#1’ sharing the heat duty of benzene column reboiler and benzene pre-heater in sequence) was the second most economic case among the study cases. ‘Scenario#3-Case#1’ results 42% more TIC than ‘Scenario#1-Case#1’(the comparative case in this study), however, this case results 20% less AOC and 19% less TIC plus 20 years’ operation cost than ‘Scenario#1-Case#1’ which means the long-term cost competitiveness.; The distillation process is world-widely utilized in the separation of mixtures. However, due to the intrinsic thermodynamic inefficiency in this process, many studies have been performed to improve distillation’s inefficiency. In connection with the prior studies, the energy optimization was performed in BTX fractionation process utilizing Pinch Technology. Heat exchanging networks, the heat exchanging matches between process-process flows, have been developed using Aspen Energy Analyzer® simulator in the technical application of Pinch Technology. Based on the developed heat exchanging networks, the feasible process configurations were simulated by Aspen HYSYS® process simulator. Total 10 scenario-cases were derived as the energy optimization cases. Sizing and cost estimation for major equipments such as columns, heat exchangers, pumps, vessels and steam ejector were performed based on the Aspen HYSYS® process simulation results. Total investment cost(TIC) was estimated from the calculated total equipment cost(TEC). Annual operation cost(AOC) was calculated based on the utility consumption of cooling water, MP steam and electricity. The economic evaluation was performed in terms of the total investment cost(TIC) plus 20 years’ operation cost. ‘Scenario#3-Case#1’(toluene column pressurized operation up to 2kg/cm2g with the hot process flow of 153℃ in toluene column top sharing the heat duty of benzene column reboiler) was the most economic case among the study cases. ‘Scenario#3-Case#2’(same process condition with ‘Scenario#3-Case#1’ sharing the heat duty of benzene column reboiler and benzene pre-heater in sequence) was the second most economic case among the study cases. ‘Scenario#3-Case#1’ results 42% more TIC than ‘Scenario#1-Case#1’(the comparative case in this study), however, this case results 20% less AOC and 19% less TIC plus 20 years’ operation cost than ‘Scenario#1-Case#1’ which means the long-term cost competitiveness.