Operability of an autothermal fixed-bed catalytic reactor within a Heat-Exchanger Network (HEN) i... more Operability of an autothermal fixed-bed catalytic reactor within a Heat-Exchanger Network (HEN) is investigated. A retrofit HEN is designed by considering the critical temperature deviations that cause run-away behavior for the reactor. The flexible retrofit design is of minimum cost (area) and keeps both the hot-spot temperature (maximum temperature rise) in the reactor within a strict safety margin and the
Nonlinear Model Predictive Control (NMPC) of a Heat-Exchanger Network (HEN) is studied. For this ... more Nonlinear Model Predictive Control (NMPC) of a Heat-Exchanger Network (HEN) is studied. For this purpose, an optimal retrofit design of the HEN is accomplished, and thus, bypasses as control variables are placed in order to satisfy steady-state hard/soft target-temperature constraints. The NMPC scheme, in which the nonlinear distributed-parameter HEN model is solved sequentially by referring to an algebraic steady-state-optimization model,
A distributed-parameter model of multi-tube, single-pass heat exchangers are used to construct th... more A distributed-parameter model of multi-tube, single-pass heat exchangers are used to construct the dynamic model of a heat-exchanger network (HEN). Based on the control-vector parameterization technique, open-loop (time-dependent bypass manipulation) and closed-loop (target-temperature dependent bypass manipulation) centralized optimal-control schemes are developed and tested. The parameterizations are done in such a way that the manipulated variables approach and eventually match the
Semi-batch deterpenation of origanum oil (Origanum Munituflorum) by dense (sub/supercritical) CO2... more Semi-batch deterpenation of origanum oil (Origanum Munituflorum) by dense (sub/supercritical) CO2 was studied in an unpacked column with two temperature zones which were applied to column's upper and lower sections. Experimental results at combinations of 70 and 85 bar pressure and 38 and 55°C temperature levels were reported. The results were discussed in terms of 14 major components, and the
Journal of The American Oil Chemists Society, 1994
Effects of temperature (at 35, 45 or 55°C) and pressure (10–110 atm) on the relative distribution... more Effects of temperature (at 35, 45 or 55°C) and pressure (10–110 atm) on the relative distribution coefficients of the twelve key components of spearmint oil (essential oil ofMentha cardiaca; Scotch spearmint) at equilibrium in dense CO2 were investigated under conditions ranging from subcritical to supercritical regions. Effects of vapor pressure, molecular weight and polarity of the key components on their equilibrium distributions in sub/supercritical CO2 are discussed. At 35°C, all key components of spearmint oil are equally soluble in dense CO2 within the 12–102 atm pressure region. At 45 and 55°C, the key components are equally soluble for pressures greater than about 60 atm. However, around either 45°C/27 atm or 55°C/35 atm conditions, the relative distribution coefficients of all monoterpene hydrocarbons and of isomenthone (an oxygenated monoterpene) exhibit maxima, which are due to significantly higher vapor pressures of these components and significantly lower solvating power of the dense-gas solvent at these particular temperatures and pressures. Vapor-pressure effects, coupled with the decrease in solvating power, dominate the effects of polarity and molecular mass of the key components. Deterpenation of spearmint oil with dense CO2 is possible around either 45°C/27 atm or 55°C/35 atm, where the monoterpene hydrocarbons tend to concentrate in the CO2-rich phase.
The reaction of soybean oil with aqueous KMnO4 solution, in the presence of dense CO2, is investi... more The reaction of soybean oil with aqueous KMnO4 solution, in the presence of dense CO2, is investigated by monitoring the amount of carbon–carbon double bonds and the fatty acid distribution of soybean oil. Experiments are performed with soybean oil and a model compound (methyl oleate) at 25 and 50°C and 70, 120 and 130bar. Reactor configuration (batch and semi-batch), reaction time, and product-storage period on the extent of the reaction are studied. With the semi-batch configuration, water feed rates ranging from 0.023 to 0.250ml/min are studied. Effect of reaction time is investigated with batch periods of 1, 3, 8, 12, 16, 24, 32 and 40h. Physical inspections and tests, as well as instrumental analysis are carried out on the soybean-oil-derived products, which are observed to change their characteristics in time in storage vials. The consumption of soybean triglyceride double bonds (STDB) are observed to increase from 23.5 to 32.6%, when the water feed rate in the semi-batch experiments was increased from 0.023 to 0.250ml/min. A saturation behavior is observed for the consumption of STDB with increasing batch reaction time. STDB consumption is 8% for one-hour reaction time, increasing to 30.1% for 16h and 42% for 40h. The samples obtained continued to react during storage, losing more than 80% of their carbon–carbon double bonds and attaining a rubber-like structure. Since there is no permanganate remaining in the collected samples, the change in the remaining fatty acid distribution and the observations about the product physical properties suggest that the depletion of STDB is due to air-oxidation polymerization, possibly initiated at the oil–water interface and accelerated by permanganate in the presence of dense CO2.
In the heat-exchanger network (HEN) literature, synthesis, design, and flexibility analyses of HE... more In the heat-exchanger network (HEN) literature, synthesis, design, and flexibility analyses of HENs are done independently from processes to which HENs are integrated. Such analyses are made mostly based on nominal operating conditions at which the HEN's source-and ...
Operability of an autothermal fixed-bed catalytic reactor within a Heat-Exchanger Network (HEN) i... more Operability of an autothermal fixed-bed catalytic reactor within a Heat-Exchanger Network (HEN) is investigated. A retrofit HEN is designed by considering the critical temperature deviations that cause run-away behavior for the reactor. The flexible retrofit design is of minimum cost (area) and keeps both the hot-spot temperature (maximum temperature rise) in the reactor within a strict safety margin and the
Nonlinear Model Predictive Control (NMPC) of a Heat-Exchanger Network (HEN) is studied. For this ... more Nonlinear Model Predictive Control (NMPC) of a Heat-Exchanger Network (HEN) is studied. For this purpose, an optimal retrofit design of the HEN is accomplished, and thus, bypasses as control variables are placed in order to satisfy steady-state hard/soft target-temperature constraints. The NMPC scheme, in which the nonlinear distributed-parameter HEN model is solved sequentially by referring to an algebraic steady-state-optimization model,
A distributed-parameter model of multi-tube, single-pass heat exchangers are used to construct th... more A distributed-parameter model of multi-tube, single-pass heat exchangers are used to construct the dynamic model of a heat-exchanger network (HEN). Based on the control-vector parameterization technique, open-loop (time-dependent bypass manipulation) and closed-loop (target-temperature dependent bypass manipulation) centralized optimal-control schemes are developed and tested. The parameterizations are done in such a way that the manipulated variables approach and eventually match the
Semi-batch deterpenation of origanum oil (Origanum Munituflorum) by dense (sub/supercritical) CO2... more Semi-batch deterpenation of origanum oil (Origanum Munituflorum) by dense (sub/supercritical) CO2 was studied in an unpacked column with two temperature zones which were applied to column's upper and lower sections. Experimental results at combinations of 70 and 85 bar pressure and 38 and 55°C temperature levels were reported. The results were discussed in terms of 14 major components, and the
Journal of The American Oil Chemists Society, 1994
Effects of temperature (at 35, 45 or 55°C) and pressure (10–110 atm) on the relative distribution... more Effects of temperature (at 35, 45 or 55°C) and pressure (10–110 atm) on the relative distribution coefficients of the twelve key components of spearmint oil (essential oil ofMentha cardiaca; Scotch spearmint) at equilibrium in dense CO2 were investigated under conditions ranging from subcritical to supercritical regions. Effects of vapor pressure, molecular weight and polarity of the key components on their equilibrium distributions in sub/supercritical CO2 are discussed. At 35°C, all key components of spearmint oil are equally soluble in dense CO2 within the 12–102 atm pressure region. At 45 and 55°C, the key components are equally soluble for pressures greater than about 60 atm. However, around either 45°C/27 atm or 55°C/35 atm conditions, the relative distribution coefficients of all monoterpene hydrocarbons and of isomenthone (an oxygenated monoterpene) exhibit maxima, which are due to significantly higher vapor pressures of these components and significantly lower solvating power of the dense-gas solvent at these particular temperatures and pressures. Vapor-pressure effects, coupled with the decrease in solvating power, dominate the effects of polarity and molecular mass of the key components. Deterpenation of spearmint oil with dense CO2 is possible around either 45°C/27 atm or 55°C/35 atm, where the monoterpene hydrocarbons tend to concentrate in the CO2-rich phase.
The reaction of soybean oil with aqueous KMnO4 solution, in the presence of dense CO2, is investi... more The reaction of soybean oil with aqueous KMnO4 solution, in the presence of dense CO2, is investigated by monitoring the amount of carbon–carbon double bonds and the fatty acid distribution of soybean oil. Experiments are performed with soybean oil and a model compound (methyl oleate) at 25 and 50°C and 70, 120 and 130bar. Reactor configuration (batch and semi-batch), reaction time, and product-storage period on the extent of the reaction are studied. With the semi-batch configuration, water feed rates ranging from 0.023 to 0.250ml/min are studied. Effect of reaction time is investigated with batch periods of 1, 3, 8, 12, 16, 24, 32 and 40h. Physical inspections and tests, as well as instrumental analysis are carried out on the soybean-oil-derived products, which are observed to change their characteristics in time in storage vials. The consumption of soybean triglyceride double bonds (STDB) are observed to increase from 23.5 to 32.6%, when the water feed rate in the semi-batch experiments was increased from 0.023 to 0.250ml/min. A saturation behavior is observed for the consumption of STDB with increasing batch reaction time. STDB consumption is 8% for one-hour reaction time, increasing to 30.1% for 16h and 42% for 40h. The samples obtained continued to react during storage, losing more than 80% of their carbon–carbon double bonds and attaining a rubber-like structure. Since there is no permanganate remaining in the collected samples, the change in the remaining fatty acid distribution and the observations about the product physical properties suggest that the depletion of STDB is due to air-oxidation polymerization, possibly initiated at the oil–water interface and accelerated by permanganate in the presence of dense CO2.
In the heat-exchanger network (HEN) literature, synthesis, design, and flexibility analyses of HE... more In the heat-exchanger network (HEN) literature, synthesis, design, and flexibility analyses of HENs are done independently from processes to which HENs are integrated. Such analyses are made mostly based on nominal operating conditions at which the HEN's source-and ...
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