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
A method for optimal retrofit design of heat-exchanger networks that do not posses control variab... more A method for optimal retrofit design of heat-exchanger networks that do not posses control variables in their original structures, is presented. Bypasses, as control variables, are placed in order to satisfy hard/soft target-temperature constraint specifications with minimum increase in exchanger areas. Alternative bypass-placement configurations are compared in terms of static flexibility, cost of retrofit design, and resiliency (Morari Resiliency Index). Pairings among the bypasses and controlled target temperatures are selected for the most favorable configuration according to Relative Gain Array criterion. Final control configuration is tested under centralized and decentralized feedback control schemes. Centralized scheme satisfies hard and soft target-temperature constraints and provides smooth response.
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
We present Turkey's manufacturing-sector innovation data and, for the first time, analyze likely ... more We present Turkey's manufacturing-sector innovation data and, for the first time, analyze likely relationships among GDP growth, sectoral innovation intensities, energy consumptions, and energy-saving potentials. We detect a power-law-like relationship between the projected energy-saving potentials and realized energy consumptions of the manufacturing-sector groups. We observe that the energy consumptions of the sectors do not change significantly despite varying innovation levels during transitions from economic crisis and recovery periods. We conclude that the Turkey's manufacturing sectors' energy consumptions are insensitive to their innovation levels, or their innovation activities are not energy-efficiency-and energy-saving-oriented, reflecting Turkey's past supply-oriented energy policy. The leader innovating sectors are, nevertheless, expected to contribute more to Turkey's energy-saving and energyefficiency policies if their innovation potentials can be directed to achieve higher energy savings and energy efficiencies via government incentives within the agenda of the recent energy-efficiency and R&D laws.
Energy Service Companies (ESCOs) are private sector instruments that offer energy-/emission-impro... more Energy Service Companies (ESCOs) are private sector instruments that offer energy-/emission-improvement (energy saving, energy efficiency, energy conservation, emission reduction) projects in the developed and in some developing countries. Literature reveals that energy-/emission-improvements of countries may be related to their innovation-and R&D-activity levels. In this work, we use a literature data on the activities and the sectors targeted by ESCOs in 38 countries, summarized in terms of the age of ESCO market (AEM), number of ESCO companies (NE), and total value of ESCO projects (VE). Along with the Global Innovation Index (GII) data of the countries, we investigate the relationships among the ESCO Indicators (EIs: AEM, NE, VE, sectors targeted by ESCOs), and the Country Indicators (CIs: GII and per-capita GDP, energy consumption, CO2 emission). We observe noteworthy dependencies between the EIs and CIs. Using the simple trend equations we estimate the missing VEs in the original data. We also project, as a hint for the size and orientation of the upcoming Turkish ESCO market, the set of EIs and the distribution of the sectors that are likely to be targeted by ESCOs in Turkey.
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
A method for optimal retrofit design of heat-exchanger networks that do not posses control variab... more A method for optimal retrofit design of heat-exchanger networks that do not posses control variables in their original structures, is presented. Bypasses, as control variables, are placed in order to satisfy hard/soft target-temperature constraint specifications with minimum increase in exchanger areas. Alternative bypass-placement configurations are compared in terms of static flexibility, cost of retrofit design, and resiliency (Morari Resiliency Index). Pairings among the bypasses and controlled target temperatures are selected for the most favorable configuration according to Relative Gain Array criterion. Final control configuration is tested under centralized and decentralized feedback control schemes. Centralized scheme satisfies hard and soft target-temperature constraints and provides smooth response.
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
We present Turkey's manufacturing-sector innovation data and, for the first time, analyze likely ... more We present Turkey's manufacturing-sector innovation data and, for the first time, analyze likely relationships among GDP growth, sectoral innovation intensities, energy consumptions, and energy-saving potentials. We detect a power-law-like relationship between the projected energy-saving potentials and realized energy consumptions of the manufacturing-sector groups. We observe that the energy consumptions of the sectors do not change significantly despite varying innovation levels during transitions from economic crisis and recovery periods. We conclude that the Turkey's manufacturing sectors' energy consumptions are insensitive to their innovation levels, or their innovation activities are not energy-efficiency-and energy-saving-oriented, reflecting Turkey's past supply-oriented energy policy. The leader innovating sectors are, nevertheless, expected to contribute more to Turkey's energy-saving and energyefficiency policies if their innovation potentials can be directed to achieve higher energy savings and energy efficiencies via government incentives within the agenda of the recent energy-efficiency and R&D laws.
Energy Service Companies (ESCOs) are private sector instruments that offer energy-/emission-impro... more Energy Service Companies (ESCOs) are private sector instruments that offer energy-/emission-improvement (energy saving, energy efficiency, energy conservation, emission reduction) projects in the developed and in some developing countries. Literature reveals that energy-/emission-improvements of countries may be related to their innovation-and R&D-activity levels. In this work, we use a literature data on the activities and the sectors targeted by ESCOs in 38 countries, summarized in terms of the age of ESCO market (AEM), number of ESCO companies (NE), and total value of ESCO projects (VE). Along with the Global Innovation Index (GII) data of the countries, we investigate the relationships among the ESCO Indicators (EIs: AEM, NE, VE, sectors targeted by ESCOs), and the Country Indicators (CIs: GII and per-capita GDP, energy consumption, CO2 emission). We observe noteworthy dependencies between the EIs and CIs. Using the simple trend equations we estimate the missing VEs in the original data. We also project, as a hint for the size and orientation of the upcoming Turkish ESCO market, the set of EIs and the distribution of the sectors that are likely to be targeted by ESCOs in Turkey.
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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Papers by Ugur Akman