Process Time Constant Research Articles

Design of adaptive-PID-Smith control in the two-mixing tank series

ABSTRACT A control strategy must be developed to maintain the product composition of the two- or more-mixed-flow reactor series. In this research, a two-mixing tank series (TMTS) was utilized in the laboratory to approach the two-mixed flow reactors’ problems. Both tanks are designed to overflow so that the volume remains constant. The salt solution was directly fed to Tank 1, while the water was charged to both tanks as the mixing progressed. The output of Tank-1 flowed to Tank-2 through a rather long pipe, resulting in dead time in Tank-2. The Smith predictor was applied to overcome dead time. The PRC (process reaction curve) method was used to tune the PID (proportional-integral-derivative) parameters of Tank-1 and Tank-2. The novel composition controls, adaptive-PID (APID) and modified metaheuristic adaptive-PID (MMAPID), have been proposed and compared with conventional PID. The mathematical models were rigorously examined through XCOS simulations. The processing system is considered sensitive to changes in input disturbances since the process time constants of both tanks were quite low. The dead time of 0.5 minutes was found in Tank 2. The PID parameters produced by PRC experiments resulted in stable responses to changes in the disturbance system. As shown in the dynamic simulation study, both novel APID and MMAPID give almost the same results; their responses are faster than the conventional PID. Based on the integral absolute error (IAE) results, APID with scheduling PID parameters produced the smallest IAE and outperformed the conventional PID. The results of the study highlight APID and MMAPID potential in PID control applications for composition control in a TMTS. The combined APID-Smith and MMAPID-Smith were able to overcome the dead time well. This study creates opportunities for engineers and professionals to use cutting-edge control technologies, improving automation and chemical process industries.

Controller Design and StabilityAnalysis of Intensification Process using Analytical Exact Gain-Phase Margin approach.

The controllable intensified process has received immense attention from researchers in order to deliver the benefit of process intensification to be operated in a desired way to provide a more sustainable process toward reduction of environmental impact and improvement of intrinsic safety and process efficiency. Despite numerous studies on gain and phase margin approach on conventional process systems, it is yet to be tested on intensified systems as evidenced by the lack of available literature, to improve the controller performance and robustness. Thus, this paper proposed the exact gain and phase margin (EGPM) through analytical method to develop suitable controller design for intensified system using Proportional-Integral-Derivative (PID) controller formulation, and it was compared to conventional Direct Synthesis methods (DS), Internal Model Control (IMC), and Industrial IMC method in terms of the performance and stability analysis. Simulation results showed that EGPM method provides good setpoint tracking and disturbance rejection as compared to DS, IMC, and Industrial IMC while retaining overall performance stability as time delay increases. The Bode Stability Criterion was used to determine the stability of the open-loop transfer function of each method and the result demonstrated decrease in stability as time delay increases for controllers designed using DS, IMC, and Industrial IMC, and hence control performance degrades. However, the proposed EGPM controller maintains the overall robustness and control performance throughout the increase of time delay and outperform other controller design methods at higher time delay with [Formula: see text] uncertainty test. Additionally, the proposed EGPM controller design method provides overall superior control performance with lower overshoot and shorter rise time compared to other controllers when process time constant is smaller in magnitude ([Formula: see text]) than the instrumentation element, which is one of the major concerns during the design of intensified controllers, resulting overall system with a higher order. The desired selection of gain margin and phase margin were suggested at 2.5 to 4 and 60 °-70[Formula: see text],respectively, for a wide range of control conditions for intensified processes where higher instrumentation dynamic would be possible to achieve robust control as well. The proposed EGPM method controller is thought to be a more reliable design strategy for maintaining the overall robustness and performance of higher order and complex systems that are highly affected by time delay and high dynamic response of intensified processes.

Identification of internal polarization dynamics for solid oxide fuel cells investigated by electrochemical impedance spectroscopy and distribution of relaxation times

Reliability and durability are two major problems restricting for Solid oxide fuel cells (SOFCs) industrial applications. To ensure the long-term stability, understood the internal operation mechanism of SOFC was necessary. The polarization curve combined with the distribution of relaxation times (DRT) method to analyze the electrochemical impedance spectroscopy (EIS) was used to identify the SOFCs modulation and degradation effect through the excitation frequency. Dynamic evolution of carbon deposition process and specific time constants were determined employing EIS and DRT. Special attention was paid to the dependency between the complex reaction processes that occur during the different operation of SOFC. The corresponding frequencies of concentration and activation polarization resistances in EIS were investigated under various gas compositions. The high concentration polarization resistance caused by the addition of nitrogen and hydrogen starvation was the key limiting factor for high cell power density. The total polarization resistance increased from 1.50 Ω/cm2 to 5.26 Ω/cm2 when the H2:N2 ratio decreased from 1:0 to 1:5. The anode did not deteriorate due to the poisoning of Ni particles in a short-term tested under 0.5 A/cm2 current density when the fuel was methane.

Optimal ultrasonication process time remains constant for a specific nanoemulsion size reduction system

This paper theorizes the existence of a constant optimum ultrasound process time for any size-reduction operation, independent of process parameters, and dependent on product parameters. We test the concept using the case of ‘ultrasonic preparation of oil-in-water nanoemulsions’ as model system. The system parameters during ultrasonication of a hempseed oil nanoemulsion was evaluated by a response surface methodology, comprising lecithin and poloxamer-188 as surfactants. Results revealed that the particle size and emulsion stability was affected significantly (p < 0.05) by all product parameters (content of hempseed oil-oil phase, lecithin and polaxamer-surfactants); but was not significantly (p > 0.05) affected by process parameter (‘ultrasonication process time’). Next, other process parameters (emulsion volume and ultrasonic amplitude) were tested using kinetic experiments. Magnitude of particle size reduction decreased with increasing ‘ultrasonication process time’ according to a first order relationship, until a minimum particle size was reached; beyond which ultrasonication no longer resulted in detectable decrease in particle size. It was found that the optimal ultrasonication process time (defined as time taken to achieve 99% of the ‘maximum possible size reduction’) was 10 min, and was roughly constant regardless of the process parameters (sample volume and ultrasonic amplitude). Finally, the existence of this constant optimal ultrasonication process time was proven for another emulsion system (olive oil and tween 80). Based on the results of these case studies, it could be theorized that a constant optimum ultrasonication process time exists for the ultrasonication-based size-reduction processes, dependent only on product parameters.

A Study on Lithium Hydroxide Recovery Using Bipolar Membrane Electrodialysis

Bipolar electrodialysis was used in a process of desalting a lithium sulfate solution, converting it to lithium hydroxide and sulfuric acid, and concentrating and recovering them. The effects of the experimental variables such as applied voltage, the concentration of electrode solution, the concentration of raw material solution, volume ratio, and impurity were confirmed. The optimum conditions were investigated by comparing the conversion(%) of lithium hydroxide and sulfuric acid, the process time, and energy consumption. As the applied voltage was increased, the energy consumption tended to increase, but the processing time decreased significantly. As the concentration of lithium sulfate in the raw material solution increased, the conversion(%) of lithium hydroxide decreased. As the concentration of lithium sulfate increased, the energy consumption did not increase linearly, and energy consumption increased significantly. When a raw material solution of 0.5 M Li2SO4 or more is used in the bipolar electrodialysis process, an applied voltage of 25 V is preferable. As the applied voltage increased at a constant process time, the conversion(%) of LiOH and H2SO4 increased. Regarding the effect of the electrode solution concentration, when a 5.0 wt% electrode solution was used rather than a 3.0 wt% electrode solution, energy consumption decreased by more than 10%. When the volume of the raw material solution was increased, the processing time required for desalting increased. By using a low concentration raw material solution, it was confirmed that it was simultaneously possible to recover and concentrate lithium hydroxide and sulfuric acid through volume ratio control. When the raw material solution contained Na as an impurity, it was converted to NaOH with a surface LiOH, and it was not possible to separate the lithium and sodium.

An intensity-modulated photocurrent spectroscopy study of the charge carrier dynamics of WO3/BiVO4 heterojunction systems

Synergistic effects as a result of combining different photoactive materials provide a promising pathway to improve the photoelectrochemical performance in heterojunction devices for solar water splitting. The photoelectrochemical characteristics of tungsten trioxide (WO3) and bismuth vanadate (BiVO4) have been studied, comparing the single-phase materials with two heterojunction systems based on a WO3 underlayer and a thin, spin-coated BiVO4 top layer, using two types of underlayer: (i) a nanorod-based WO3 substrate prepared by hydrothermal methods (nr-WO3/BiVO4); and (ii) a spin-coated thin, compact WO3 substrate (pl-WO3/BiVO4). Intensity-modulated photocurrent spectroscopy (IMPS) was used to determine the charge separation efficiency, internal and external quantum efficiencies, and process time constants for the four systems in a phosphate buffer at pH 7, both without and with an added hole scavenger, Na2SO3. The heterojunction systems show excellent performance, which is ascribed to the superior capability of WO3 to extract photogenerated electrons from the BiVO4 film that acts as the main absorber. IMPS convincingly shows that the heterojunction configuration prevents surface recombination at the BiVO4 /electrolyte interface, as well as the detrimental surface modification generally observed for WO3 photoelectrodes. The improved electron transport properties of the nr-WO3 substrate and the large area of the heterojunction interface result in better performance for nr-WO3/BiVO4, where at 455 nm water photo-oxidation is quantitative. For the single-phase BiVO4 photoelectrodes, an interesting photocurrent switching phenomenon is observed in the presence of the hole scavenger, indicating the intricate interplay between electron trapping and hole charge transfer; this phenomenon is prevented by the heterojunction structure because of the rapid electron extraction by WO3. These results show that IMPS gives detailed information on the reasons for the excellent performance of heterojunction systems, providing opportunities to design new, more efficient solar water splitting systems.

Non-Dimensional Feature Engineering and Data-Driven Modeling for Microchannel Reactor Control

Catalytic plate microchannel reactors (CPRs) are a promising means for modular hydrogen/fuels production from distributed natural gas resources. However, the equipment miniaturization presents challenges for process control, including spatially-distributed models, limited availability of measurements, and fast process time constants. In the present paper, we investigate the use of data-driven models—specifically, artificial neural networks (ANNs)—to estimate temperature “hotspots” within CPRs. We prescribe nonlinear transformations of the model inputs in the form of well-known dimensionless quantities (e.g., Reynolds number), and we show that these engineered features can improve the prediction capability of computationally parsimonious ANNs using a first-principles reactor model. Finally, we present a simulation case study that demonstrates the use of a trained ANN for inferential model predictive control.

UV-induced photosensing characteristics of SiC and GaN nanowires

PurposeThis study aims to investigate photosensing characteristics of SiC and GaN nanowire-based devices through exposure to UV light. The photocurrent transients have been modeled to determine rise and decay process time constants. The 1D-semiconductor nanowires can exhibit higher light sensitivity compared to bulk materials because of their large surface area to volume ratio and the quantum size effects.Design/methodology/approachNanowire devices have been fabricated through dielectrophoresis for integrating nanowires onto pre-patterned electrodes (10 nm Ti/ 90 nm Au) with a spacing about 3 µm onto SiO2/Si (doped) substrate. The photocurrent measurements were carried out under room temperature conditions with UV light of 254 nm wavelength.FindingsSiCNWs yield very short rise and decay time constants of 1.3 and 2.35 s, respectively. This fast response indicates an enhanced surface recombination of photoexcited electron-hole pairs. Conversely, GaNNWs yield longer rise and decay time constants of 10.3 and 15.4 s, respectively. This persistent photocurrent suggests a reduced surface recombination process for the GaNNWs.Originality/valueHigh selective UV light sensitivity, small size, very short response time, low power consumption and high efficiency are the most important features of nanowire-based devices for new and superior applications in photodetectors, photovoltaics, optical switches, image sensors and biological and chemical sensing.

AISI 5140 steel nitriding in a plasma of a non-self-sustaining arc discharge with a thermionic cathode under the pulse action of ions

Steel AISI 5140 was exposed to pulsed (50 kHz) low-energy (up to 1 kV) nitriding in the plasma of a non-self-sustained arc discharge with a hot hollow cathode in a pure nitrogen atmosphere. The aim was to investigate the effect of the ion energy (pulse amplitude) and ion current density on the nitride layer thickness and on the depth of diffusion saturation with nitrogen. Experiments were also performed to study the effect of the ion energy and ion current density on the efficiency of nitriding at a constant specimen temperature and constant process time.

Performance of core thermocouples of FBTR – A technique for predicting accurate temperature for known transients in the presence of measurement delays

Abstract FBTR is a 40 MWt research reactor, located at Kalpakkam, near Chennai, India. The reactor has been in operation since 1985 and has seen a maximum operating power of 30.2 MWt till July 2018. The fuel sub-assemblies (FSA) are located vertically in the grid plate along with other types of sub-assemblies namely reflectors and blanket sub-assemblies. Sodium enters the sub-assemblies from the bottom and exits through the top. There are 84 positions where thermocouples are provided to measure the temperature of the sodium jet passing out from the FSA’s. The mineral-insulated metal-sheathed ANSI Type K thermocouples are exposed to intense neutron fluence as well as gamma dosage. In this paper, the performance of the core thermocouples since the first criticality of FBTR has been comprehensively presented. A few problems, including failure of bare thermocouples (installed without thermo-wells), presence of normal-mode electrical noise in the signals etc., have been faced in FBTR. Suitable remedial actions have been taken for overcoming the same. Since the hot junctions of these thermocouples are inaccessible after installation, in-situ cross-calibration techniques have been employed for verifying their calibration. Using the time-domain data available during the safety actions such as simultaneous lowering-of-rods (LOR) and the dropping of all the six control rods (SCRAM), the in-situ process time-constants involved in core temperature measurement have been estimated. One of the problems faced in FBTR is that, subsequent to a reactor shut-down by LOR, the measured value of the sodium temperature difference across certain FSA’s rise above the expected value, leading to initiation of faster safety action (that is, reactor SCRAM), resulting in unwanted thermal shocks to the core components. This necessitated the need to analyze the transient behavior of the core during LOR, including the response of the core thermocouples. The whole measurement process was modeled, and with that, the actual temperature rise across the FSA’s could be predicted quite accurately from the observed temperatures which are influenced by both process and measurement delays. Using the predicted behavior, it could be established that the onset of unwanted reactor SCRAM can be considerably delayed, thereby minimizing the thermal shocks to the core components.

Antibacterial Applications of Anatase TiO&lt;SUB&gt;2&lt;/SUB&gt; Nanoparticle

Many methods have been used for the preparation of nanostructured metal oxides. Here we report the synthesis of TiO2 nanoparticles by facile hydrothermal process by varying the concentration of the precursor and reaction temperature while keeping the process time constant. Morphological, structural and optical studies were carried out by scanning electron microscopy equipped with energy dispersive spectroscopy, X-ray powder diffraction spectroscopy and VU-Vis-NIR spectroscopy. Morphological and compositional analysis reveal that the prepared nanoparticles are highly pure with an approximate average particle size 5-15nm. XRD studies showed their crystalline structure and the sizes around 5 nm, while the optical absorption studies in the photon wavelength range 300-600 nm reveal that the strong absorbance peak is positioned at around 3.5 eV nm whereas visible energy is almost transparent for the materials. Finally, the antibacterial effect of TiO2 nanoparticles has been studied. Plating technique was used to determine lowest concentration that prevent or inhibit growth of bacteria. This technique of TiO2 nanoparticle was used against most common organisms which cause wound infection including: MRSA, E. coli and Pseudomonas aeruginosa. Different concentrations of TiO2 nanoparticles were used 100 μg/ml, 200 μg/ml, 400 μg/ml, 600 μg/ml and 800 μg/ml. Inhibition of bacteria was different for prepared TiO2 samples due to different concentration of the precursors and synthesis temperature.

A novel approach for supercapacitors degradation characterization

Abstract A novel approach to analyze electrochemical impedance spectroscopy (EIS), based on evolutionary programming, has been utilized to characterize supercapacitors operation mechanism and degradation processes. This approach poses the ability of achieving a comprehensive study of supercapacitors via solely AC measurements. Commercial supercapacitors were examined during accelerated degradation. The microstructure of the electrode-electrolyte interface changes upon degradation; electrolyte parasitic reactions yield the formation of precipitates on the porous surface, which limit the access of the electrolyte ions to the active area and thus reduces performance. EIS analysis using Impedance Spectroscopy Genetic Programming (ISGP) technique enables identifying how the changing microstructure is affecting the operation mechanism of supercapacitors, in terms of each process effective capacitance and time constant. The most affected process is the transport of electrolyte ions at the porous electrode. Their access to the whole active area is hindered, which is shown in our analysis by the decrease of the capacitance gained in the transport and the longer time it takes to penetrate the entire pores depth. Early failure detection is also demonstrated, in a way not readily possible via conventional indicators. ISGP advanced analysis method has been verified using conventional and proven techniques: cyclic voltammetry and post mortem measurements.

Instant vegetable from osmo-air drying of jimikand (A. campanulatus) in NaCl solution: nutritional, functional, micro-structural and other quality aspects.

The aim of this work was to study the effect of osmotic dehydration on the quality of jimikand which can be used as an instant vegetable to get its nutritional and functional benefits. Osmotic dehydration was applied as pre-treatment to hot-air drying for increasing palatability, mass transfer improvement and minimizing nutritional losses. To see the effect of osmotic dehydration on various quality parameters, conditions of osmotic dehydration selected were osmotic solution concentrations (5, 10 and 15% w/w) and temperatures (40, 50 and 60°C) for constant process time (80min) on the basis of mass transfer analysis. The observed values of hardness, oxalate content and water activity of osmo-dried samples varied from 66.04±14.5 to 79.12±14.8N, 60.0±0.40 to 69.1±0.65mg/100g, 0.911±0.001 to 0.826±0.001, respectively, and found less as compared to fresh sample, i.e. 131.12±9.5N, 110.5±0.78mg/100g and 0.990±0.00 respectively. Rehydration ratio of fresh sample was 3.52±0.03 and varied from 2.82±0.06 to 3.57±0.10 for osmo-dried samples being higher at lower concentrations and temperatures. The best conditions of osmotic dehydration found were 10% NaCl, 50°C temperature and 80min duration on the basis of appreciable mass transfer, lowest oxalate content, water activity, better rehydration, textural and sensory quality. The selected osmo-dried sample was better due to low anti-nutritional content, less micro-structural damage and appreciably comparable to fresh hot-air dried in terms of total phenol, antioxidant activity, and other quality parameters.

Performance Analysis and Comparison of Different Tuning Strategies of PI Controller in Conical Tank

Background/Objectives: An adaptive Proportional Integral (PI) controller for a conical tank liquid level process is simulated in MATLAB platform. Method/Statistical Analysis: The Scheduled PI and Internal model control (IMC) based PI performance are compared in terms of settling time rise time, overshoot, Integral of Squared Error (ISE), Integral of Absolute Error (IAE), Integral Time Absolute Error (ITAE) and disturbance rejection. For IMC based PI tuning, the exact model of the process obtained by on line estimation of process gain and time constant. Findings: The IMC based tuning procedure ensures good performance by Proportional and Integral (PI) controller. The Ziegler Nichols (ZN) tuning rules and estimation based tuning are used for scheduled Proportional and Integral (PI) and internal model control based PI controller. Applications/Improvements: Derivative controller can be added to this PI controller for distillation process. Keywords: Disturbance Rejection, IMC based PI, Integral of Square Error, Scheduled PI

An investigation on pulsed DC plasma electrolytic oxidation of cp-Ti and its corrosion behaviour in simulated body fluid

Titania coating was produced on commercially pure titanium by a pulsed DC plasma electrolytic oxidation (PEO) process in an aqueous electrolyte containing 5 g/l trisodium orthophosphate and 2 g/l potassium hydroxide. Four different PEO coatings were fabricated with two different duty cycles (10% and 95%) and two different current frequencies (50 Hz and 1000 Hz) while maintaining a constant current density and process time of 150 mA/cm2 and 8 min, respectively. The phase composition, roughness, thickness, surface morphology and cross-sectional microstructure of the coating were assessed using X-ray diffraction (XRD), optical profilometer, eddy current thickness gauge and scanning electron microscope (SEM). The scratch resistance of the coating was assessed by a scratch test. The corrosion behaviour of the coating was studied in a Kokubo 7.4 pH simulated body fluid (SBF) solution by open circuit potential (OCP) measurement, potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) with equivalent circuit modelling and EIS curve fitting. Among the coatings, the coating produced at 10% duty–50 Hz frequency had a lower thickness, poor corrosion resistance (icorr, 1.9 × 10− 4 mA/cm2) and poor scratch resistance (Lc, 15 N) while the coating produced at 95% duty–1000 Hz frequency showed higher corrosion resistance (icorr, 3.3 × 10− 6 mA/cm2), higher scratch resistance (Lc, 26 N) and had a dense coating. The coating with highest corrosion resistance also showed good wettability (contact angle, 61 ± 3°) and apatite forming ability under bioactivity test.

Optimization of sulfur adsorption over Ag-zeolite nanoadsorbent by experimental design method

Environmental protection has mentioned the need to cut out all of fuels sulfur compounds. One of the most important processes that affect sulfur removal in atmospheric condition is the interaction of liquid fuels with solid sulfur removal adsorbents such as zeolites. To investigate the nano-AgX-zeolite efficiency for the sulfur adsorption process, a set of experimental tests was arranged and conducted by Box–Behnken design software, in an adsorption laboratory setup. The selected variables comprised metal percent, adsorption temperature and calcination temperature. The parameter levels were 0.5–10 %, 30–120 and 200–500 °C, respectively. The experiment results were used to find the statistical model. The results demonstrate that the sulfur concentration level is 48.36 ppm in the last product at 83 °C for adsorption temperature, 5.53 % for metal percent and 436 °C for calcination temperature in constant pH and constant process time.

Linear friction welding of dissimilar AA6082 and AA2011 aluminum alloys: microstructural characterization and design guidelines

This paper presents the results of an experimental and numerical campaign on Linear Friction Welding of dissimilar AA2011-T8 and AA6082-T6 aluminum alloys. Experimental tests were carried out with constant oscillation amplitude and process time. Varying oscillation frequency, interface pressure, specimen geometry and mutual position were used. Grain size measurements, HV tests and EDX analysis were considered to characterize the microstructure of the joints as a function of the input process parameters. A thermal numerical model was utilized to predict the temperature profiles in the joints during the process. The obtained results allowed the identification of four weld categories: sound joints, “bonding limit” condition and two different unwelded joints. The investigation of the causes of the different joint behavior permitted to obtain a few design guidelines on the LFW of dissimilar alloys with different geometry.

Dynamic modelling, identification and preliminary control analysis of an amine-based post-combustion CO2 capture pilot plant

Solvent-based post combustion CO2 capture (PCC) is considered as a mature technology for dealing with CO2 emissions from fossil-fired power plants. In this study, a mathematical black box model is developed to analyse the dynamic responses of a PCC pilot plant. The model identification reported the dynamics of variables of the key units in the plant, the absorber, rich/lean heat exchanger and desorber. Pilot plant dynamic data were used to develop a data-driven model for each unit operation. Individual models were integrated to produce a simplified 4 × 3 PCC process model of the PCC plant. The fastest dynamic with a time constant ranging from 2 to 3 min featured in the relationship between power plant flue gas flow rate and CO2 concentration in the absorber off gas. Whereas, the slowest response with a process time constant between 9 and 27 min occurred in CO2 concentration at the top of the stripper due to changes in reboiler heat duty. Preliminary control analysis using relative gain array (RGA) analysis suggested that carbon capture efficiency, CC (%), and energy performance, EP (MJ per kg of CO2 captured), can be controlled by manipulating the lean solvent flow rate and reboiler heat duty, respectively. The proposed control structure was tested and tracked CC and EP random set point step changes in the range between 7–25 h and 4–5 h respectively. This study contributes to understanding transient variable behaviours in PCC plants; concurrent with current industrial requirements for controllability and flexible operation of PCC plants, in response to the dynamics of power plant load, electricity and carbon prices.

ON-LINE CONTROLLER TUNING FOR CRITICALLY DAMPED SOPTD SYSTEMS

A method is proposed to identify the model parameters of a stable, critically damped second-order plus time delay system. The method uses a step response of the closed-loop system using a PID controller. The two dominant poles of the closed-loop model were obtained using the step response. The process gain was calculated using the steady-state deviation values of the output and the input variable of the process. Using the identified dominant poles in the derived closed-loop characteristic equations, the relevant two nonlinear algebraic equations were derived to calculate the process delay and time constant. Three simulation examples were considered to show the effectiveness of the proposed method. The open-loop and as well as the closed-loop responses of the process were compared with those of the identified model and of the controller design based on the models. A significant improvement was obtained in the performance of the critically damped SOPTD model over that of the FOPTD model. The identified model parameters by the present method were compared with those of the relay auto-tuning method. A simulation study on a nonlinear bio reactor is also reported.

Experimental Study of the Dynamic Behavior of the Stripping Column for Post-combustion CO2 Capture with Monoethanolamine

CO2 capture from coal-fired power plants using a monoethanolamine (MEA) solution is one of the most promising technologies for CO2 abatement. The MEA absorption process for CO2 capture from power plants is an inherently dynamic system that is affected by the load variations in the upstream power plant because of fluctuations in electricity demand. This paper presents an experimental study of the dynamic behavior of a stripping column after various disturbances. Tests of negative and positive steps of different magnitudes in the reboiler heat duty were conducted to determine the process gain and time constant. The dynamic behavior of the desorption process was also investigated using ramp tests of different magnitude in the reboiler heat duties and feed solvent temperatures. The results show that the desorption process response to the heat duty could be approximated as a first-order time delay model. The solvent holdup time in the reboiler was the dominant factor controlling the system response time. The results also show that the CO2 capture is a nonlinear process.