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D epartment of Chemical Engineering Budapest University of Technology and Economics and Research Group of Technical Chemistry Hungarian Academy of Sciences. O PTIMAL DESIGN OF INTEGRATED SEPARATION SYSTEMS Zsolt Fonyo. 23 March 2004, Trondheim, Norway. Research activities
Department of Chemical Engineering Budapest University of Technology and Economics andResearch Group of Technical Chemistry Hungarian Academy of Sciences OPTIMAL DESIGN OF INTEGRATED SEPARATION SYSTEMS Zsolt Fonyo 23 March 2004, Trondheim, Norway
Research activities • DISTILLATION AND ABSORPTION • Determination of Vapour-Liquid Equilibria and design of Packed Col • umns. • Development on distillation and absorption technologies • Modelling and calculation of thermodynamic properties • Modelling of batch and continuous countercurrent separation processes • EXTRACTION AND LEACHING • Kinetics of Soxhlet-type and Supercritical Solid-Liquid Extraction of Natural Products. Mathematical modelling and optimization of the process. • Supercritical fluid extraction equipment and R&D capabilities • REACTIONS • Mathematical modelling of residence time distribution and chemical reactions • MIXING OF LIQUIDS
PROCESS DESIGN AND INTEGRATION • Feasibility of distillation for non/ideal systems • Hybrid separation systems • Reactive distillation • Design of Energy Efficient Distillation Processes • Energy integrated distillation system design enhanced by heat pumping and dividing wall columns • Energy recovery systems • A global approach to the synthesis and preliminary design of • integrated total flow-sheets • Process Integration in Refineries for Energy and Environmental Management
CONTROL AND OPERABILITY • Assessing plant operability during process design • Transformation of Distillation Control Structures • ENVIRONMENTALS • Waste reduction in the Chemical Industry • CLEAN TECHNOLOGIES • Membrane separations • Cleaning of waste water with physico-chemical tools. • Solvent recovery • Synthesis of mass exchange networks with mixed integer nonlinear programming • Economic and controllability study of energy integrated separation schemes • Process synthesis of chemical plants
Analysis of energy integrated separations (distillation based) Synthesis of Mass Exchange Networks Using Mathematical Programming Solvent Recovery from Non-Ideal Quaternary Mixtures with Extractive Heterogeneous-Azeotropic Distillation 23 March 2004, Trondheim, Norway
Integrated process design • Challenge in chemical engineering • Economical and environmental aspects • Heat integration (HEN) & mass integration (MEN) • Several synthesis strategies • The design needs CAPE
Analysis of energy integrated separations (distillation based) (Economic and Controllability Analysis of Energy-Integrated Distillation Schemes) Budapest University of Technology and Economics Department of Chemical Engineering
Aims of the work Separation of ternary mixture by energy-integrated distillation schemes Optimization of the schemes Economic evaluation and comparison of the schemes Optimal schemes are investigated for controllability features Estimation of the environmental effects
Case study • Mixture: (Ethanol – n-Propanol– n-Butanol) • Feed compositions: • Case 1: (0.45/ 0.10/0.45) • Case 2: (0.33/ 0.33/0.33) • Case 3: (0.10/ 0.80/0.10) • Product purity specifications: 99 mole %
C *Case 1 *Case 2 *Case 3 A B Composition Triangle
HYSYS Process Simulator Modeling of the schemes Steady-state simulation Dynamic simulation Techniques and assumptions • NRTL and UNIQUAC activity models are used • The impurities in B product stream are symmetrically distributed. • Total condensers and reboilers are used. • Exchange min. approach temperature (EMAT)=8.5 oC. • Valve trays (Glitsch type) are used as column internals.
Conventional distillation schemes Direct sequence Base case for comparison Indirect sequence
Conventional-heat integration Forward heat integration direct sequence (DQF) Backward heat integration direct sequence (DQB)
Thermo-coupling Petlyuk column (SP)
Sloppy separation sequences Forward heat integration (SQF)
Sloppy separation sequence, backward heat integration (SQB)
The objective function is total annual cost (TAC), which includes annual operating and capital costs.
Estimation of capital cost Douglas, J. M., Conceptual design of chemical processes, McGraw-Hill Book Company Marshall & Swift index: (1056.8/280) Project life: 10 years Sizing of columns and heat exchangers are estimated by HYSYS flowsheet simulator
Case study Mixture: ethanol n-propanol n-butanol Equimolar feed composition (0.333, 0.333, 0,333) Product purity specification: 99 m%
Comparison of TAC savings (%) I D base case DQF DQB SP SQF SQB
Comparison of costs ($/yr) Case (2), (0.33/0.33/0.33) SP SQF SQB D I DQF DQB
· Energy-integrated schemes are more economical than the best conventional schemes. · Operating cost proved to be dominant on TAC. · Petlyuk column is the best in TAC saving at low concentration of the middle component (case 1) with 33 % . · The heat requirements for the separation increases with increasing concentration of the middle component, and heat-integrated schemes prove to be the best. · The maximum TAC saving is achieved in case 3 with 53 % by sloppy sequence with backward heat integration. Results of the economic study
Dynamic simulations Open-loop Closed-loop Controllability study • Selection of controlled variables & manipulated variables, • Degrees of freedom analysis Steady-state control indices • Niederlinski index (NI) • Morari index (MRI) • Condition number (CN) • Relative gain array (RGA)
Evaluation of steady state indices • Base case D and heat-integrated schemes (DQF and DQB) show less interactions. • (D1-L2-B2) manipulated set proves to be better than (L1-D2-Q2) and (L1-D2-B2) for D, DQF and DQB. • Serious interactions can be expected for the sloppy schemes (SQF, SQB and SP). • (L-S-B) manipulated set proves to better than (D-S-Q) for SP, SQF and SQB schemes.
Dynamic simulations • Feed rate disturbance: 100 100.5 kmol/h • Feed composition disturbance: • (0.33/0.33/0.33) (0.30/0.40/0.30) 1. Open composition control loops: Composition control loops are not installed
Results of open loop dynamic simulation Heat integrated (DQB) column, open loop, feed rate disturbance
Summary of open-loop simulation results • quite similar dynamic behaviour but • sloppy backward heat integrated (SQB) is the slowest scheme
2. Closed composition control loops: Composition and level controller are installed P-controller For level control For composition control PI-controller Controllers tuning by Tyerus-Luyben cycling method • Overshoot, settling time, and their product are evaluated.
Results of closed-loop dynamic simulation Heat integrated (DQB) column, closed loop (D1-L2-B2), feed rate disturbance
Heat integrated (DQB) column, closed loop (D1-L2-B2), feed composition disturbance
Conclusions of closed-loop dynamic simulations • Simple energy integration (heat integration) doesn’t influence • dynamic behaviour compared to the non-integrated base case • Higher detuning factor is needed due to stronger interactions in complex distillation systems (they became slower in closed loop) • The cases, where material and energy flows (energy integration) • go into the same direction (DQF, SQF), are better than the opposite • Since the sloppy schemes show similar economic parameters, • their controllability features make the decision to the favour of SQF ! • Petlyuk columns controllability parameters are between the ones of the heat-integrated and the sloppy schemes
Estimation of the flue gas emissions The main gaseous pollutants that are considered in this work are: CO2, SO2, and NOx
Final conclusions • with energy-integration about 53 % TAC saving can be realised in case of SQF scheme • Petlyuk column has a limited TAC saving of 30-33 % in all the three feed composition cases • conventional heat-integration shows the best economic and controllability features considering all the three feed compositions
sloppy schemes show good economic features but the selection is made according to their different controllability features (SQF has better features than SQB) • economic and controllability features are to be handled simultaneously during process design.
Closed loop dynamic simulations • Simple energy integration (heat integration) doesn’t influence • dynamic behaviour compared to the non-integrated base case • more complicated systems: higher detuning factor is needed • due to stronger interactions (they became slower in closed loop) • The cases, where material and energy flows (energy integration) • go into the same direction (DQF, SQF), are better than the opposite • Since the sloppy schemes show similar economic parameters, their • controllability features make the decision to the favour of SQF (!) • Petlyuk (dividing wall) column‘s controllability parameters are • between the ones of the heat integrated and the sloppy structures.
Synthesis of Mass Exchange Networks Using Mathematical Programming Budapest University of Technology and Economics Department of Chemical Engineering
Outline I. Mass Exchange Network Synthesis (MENS) A Extension of the MINLP model of Papalexandri et al. (1994) B Comparison of the advanced pinch method of Hallale and Fraser (2000) and the extended model of Papalexandri et al. C New, fairly linear MINLP model for MENS II. Rigorous MINLP model for the design of distillation-pervaporation systems III. Rigorous MINLP model for the design of wastewater strippers Approach: Mixed Integer Nonlinear Programming (MINLP) optimisation software: GAMS / DICOPT
I. Mass Exchange Network Synthesis El-Halwagi and Manousiouthakis, AIChE Journal, Vol 35, No.8, pp. 1233-1244 Mass integration for the analogy of the concept of heat integration. Absorber, extractor etc. network synthesis (MSAs) The synthesis task: Stream data + equipment data + equilibrium data + costing Network structure lean stream flow rates min (Total Annual Cost, TAC) Previous work: sequential mathematical programming methods El-Halwagi (1997), Garrison et al. (1995) Alva-Argaez et al. (1999) early pinch methods (no supertargeting) Water pinch: Wang & Smith (1994, 1995), Kuo & Smith (1998) El-Halwagi & Manousiouthakis (1989a) El-Halwagi (1997) advanced pinch method (includes supertargeting) Hallale & Fraser (1998, 2000) simultaneous mathematical programming models Papalexandri et al. (1994) Papalexandri & Pistikopoulos (1995, 1996) Comeaux (2000); Wastewater: Benkő, Rév & Fonyó (2000)