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  • Articles  (44,231)
  • Molecular Diversity Preservation International  (29,087)
  • American Chemical Society (ACS)  (15,078)
  • Berkeley Electronic Press (now: De Gruyter)  (66)
  • Process Engineering, Biotechnology, Nutrition Technology  (44,231)
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  • 1
    Electronic Resource
    Electronic Resource
    Robust Temperature Stabilization for Fluid Catalytic Cracking Units Using Extended Kalman-Type Estimators (2006)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 1 (2006), S. 3 
    Details
    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Fluidised-bed Catalytic Cracking (FCC) units, are one of the most complex and interactive processes in the refining industry, hence they are difficult to operate and to control; on the other hand they are one of the main producers of gasoline, which is an incentive to improve operation policies. This work deals with the design of regulative control law for stabilisation of reactor and regenerator temperatures considering that kinetics terms are poorly known, which is the industrial case. This control law uses on-line estimates of the heat of reaction, obtained from Kalman-like filtering of measured temperatures. The controllers designed are similar to standard input-output linearising controllers and can be tuned by standard techniques. Performance of the estimation technique under closed-loop operation is analysed by numerical simulations, considering noisy measurements and time delay in the regenerator control input.
    Type of Medium: Electronic Resource
    URL: http://www.bepress.com/cppm/vol1/iss1/3
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  • 2
    Electronic Resource
    Electronic Resource
    A Multi-Level Methodology for Conceptual Reaction-Separation Process Design (2007)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 2 (2007), S. 2 
    Details
    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Generic technology is presented for the optimal screening of reaction and separation process interactions. The proposed scheme enables the use of particularly rich superstructure formulations that are comprised of two types of generic synthesis units with flexible representation modes. A reaction unit enables a detailed representation of the reaction and a conceptual representation of separation systems is facilitated through separation task units. Possible process design interactions are embedded in the superstructure formulations as combinations of generic units. The design options are explored using stochastic optimisation techniques suitable for this class of problems. The synthesis scheme supports the decision making process in early process design stages and prepares problem definitions for later stages. Conceptual screening functionalities reveal design insights into the performance of complex reaction-separation systems based on the limited modelling information available early in design. This enables the identification and inclusion of the relevant design information into the superstructure formulations employed in the subsequent design stages.
    Type of Medium: Electronic Resource
    URL: http://www.bepress.com/cppm/vol2/iss3/2
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  • 3
    Electronic Resource
    Electronic Resource
    Learning to Control pH Processes at Multiple Time Scales: Performance Assessment in a Laboratory Plant (2007)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 2 (2007), S. 7 
    Details
    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This article presents a solution to pH control based on model-free learning control (MFLC). The MFLC technique is proposed because the algorithm gives a general solution for acid-base systems, yet is simple enough for implementation in existing control hardware. MFLC is based on reinforcement learning (RL), which is learning by direct interaction with the environment. The MFLC algorithm is model free and satisfying incremental control, input and output constraints. A novel solution of MFLC using multi-step actions (MSA) is presented: actions on multiple time scales consist of several identical primitive actions. This solves the problem of determining a suitable fixed time scale to select control actions so as to trade off accuracy in control against learning complexity. An application of MFLC to a pH process at laboratory scale is presented, showing that the proposed MFLC learns to control adequately the neutralization process, and maintain the process in the goal band. Also, the MFLC controller smoothly manipulates the control signal.
    Type of Medium: Electronic Resource
    URL: http://www.bepress.com/cppm/vol2/iss1/7
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  • 4
    Electronic Resource
    Electronic Resource
    Inference of Chemical Reaction Networks Using Hybrid S-system Models (2007)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 2 (2007), S. 10 
    Details
    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This article demonstrates, using simulations, the potential of the S-system formalism for the inference of unknown chemical reaction networks from simple experimental data, such as that typically obtained from laboratory scale reaction vessels. Virtually no prior knowledge of the products and reactants is assumed. S-systems are a power law formalism for the canonical approximate representation of dynamic non-linear systems. This formalism has the useful property that the structure of a network is dictated only by the values of the power law parameters. This means that network inference problems (e.g. inference of the topology of a chemical reaction network) can be recast as parameter estimation problems. The use of S-systems for network inference from data has been reported in a number of biological fields, including metabolic pathway analysis and the inference of gene regulatory networks. Here, the methodology is adapted for use as a hybrid modelling tool to facilitate the reverse engineering of chemical reaction networks using time series concentration data from fed-batch reactor experiments. The principle of the approach is demonstrated with noisy simulated data from fed-batch reactor experiments using a hypothetical reaction network comprising 5 chemical species involved in 4 parallel reactions. A co-evolutionary algorithm is employed to evolve the structure and the parameter values of the S-system equations concurrently. The S-system equations are then interpreted in order to construct a network diagram that accurately reflects the underlying chemical reaction network.
    Type of Medium: Electronic Resource
    URL: http://www.bepress.com/cppm/vol2/iss1/10
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  • 5
    Electronic Resource
    Electronic Resource
    Spatial and Temporal Resolution in Data-Driven Process Modeling of an Integrated Newsprint Mill (2007)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 2 (2007), S. 13 
    Details
    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Like many globalized industries, the pulp and paper sector finds itself with an increasingly demanding clientele, who continually expect a better and cheaper product. An important design strategy being employed to address this objective is through an analysis of the vast quantity of process and product data accumulated in plant-wide data historians, in order to improve operations. Mill processes are multivariate, meaning that the interactions between the variables are as important as the variables themselves. Process relationships must therefore be modeled as a group, using an appropriate simulation technique like Multivariate Analysis (MVA), with suitable data pre-processing to account for process upsets and other disturbances. In a previous paper, using an Eastern Canadian newsprint mill as an industrial case study, we showed that it was possible to find statistically significant correlations between wood chip refiner operation, intermediate pulp quality, and final paper quality using data-driven models. This was true even though some important process parameters went unmeasured, process lags changed with time, and the operation of key equipment items changed gradually with use. The present study compares the use of different timescales and combinations of unit operations to determine which ones yield the best MVA simulations. Because plant operating data were used, and experimental design was not practical, it is possible that some of the correlations found could be attributable to coincidence. We therefore added and removed variables and time periods to explore the validity of the models. The best MVA models were obtained by using a shorter (1-hour) data timescale, although use of a weighted-average filter helped to bridge the gap between these faster readings and the slower paper quality trends.
    Type of Medium: Electronic Resource
    URL: http://www.bepress.com/cppm/vol2/iss1/13
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  • 6
    Electronic Resource
    Electronic Resource
    Optimization of the Variable Reflux Ratio in a Batch Distillation Column through a Heuristic Method (2007)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 2 (2007), S. 12 
    Details
    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The manuscript is focused on the optimization of a batch distillation column that is actually formulated in terms of control problem. The final objective is finding the optimal time-dependent reflux profile. In order to fulfill the call for simplicity and functionality from the industries, the reflux profile was approximated by means of a piece-wise function with three time intervals. A first-principles model, derived from the literature, proved to be a good trade-off between computational effort and accuracy. The capacity factor (CAP), defined as the on-specification products produced per time unit, is the performance index that must be maximized. The optimization problem was solved by a specifically modified Simplex method that demonstrated a good behavior in case of discontinuous objective function. Finally, a graphical analysis of the capacity factor was performed to show the irregularities of such a function.
    Type of Medium: Electronic Resource
    URL: http://www.bepress.com/cppm/vol2/iss1/12
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  • 7
    Electronic Resource
    Electronic Resource
    Sliding-mode Observer for Uncertainty Estimation in a Class of Chemical Reactor: A Differential-Algebraic Approach (2007)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 2 (2007), S. 10 
    Details
    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The problem of the on-line estimation of the reaction heat in a continuous stirred tank reactor from temperature measurements is addressed in this paper. The proposed uncertainty observer is based on differential algebraic techniques, such that the algebraic observability condition of the uncertainty from noisy temperature measurements is easily verified and the observer structure is very simple, which lead to feasible implementation. The observer proposed is robust against noisy measurements and sustained disturbances. The good performance of the observer is shown by means of numerical simulations and is compared with a nonlinear Luenberger-type observer.
    Type of Medium: Electronic Resource
    URL: http://www.bepress.com/cppm/vol2/iss3/10
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  • 8
    Electronic Resource
    Electronic Resource
    Passivity Based Dynamic Controllability Analysis for Multi-Unit Processes (2007)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 2 (2007), S. 7 
    Details
    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In this paper, a simple dynamic controllability analysis is developed to analyze the achievable control performance of different control structures for multi-unit processes. Based on the concept of passive systems, this approach extends the concepts of Decentralized Integral Controllability (DIC) and Block-Decentralized Integral Controllability (BDIC) so that process dynamics are considered. By using particular multipliers that represent different control structures, the frequency ranges in which perfect control may be achieved by multi-loop, multi-unit (block diagonal) and multivariable controllers are estimated. This bandwidth indicates the swiftness of the feedback control systems (e.g., the time the control systems take to reject a disturbance).
    Type of Medium: Electronic Resource
    URL: http://www.bepress.com/cppm/vol2/iss2/7
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  • 9
    Electronic Resource
    Electronic Resource
    Mathematical Modelling of the Self-Heating Process in Compost Piles (2007)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 2 (2007), S. 8 
    Details
    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: We model the increase in temperature in compost piles or landfill sites due to micro-organisms undergoing exothermic reactions. The model incorporates the heat release due to biological activity within the pile and the heat release due to the oxidation of cellulosic materials. The heat release rate due to biological activity is modelled by a function which is a monotonic increasing function of temperature over a particular range and followed by a monotone decreasing function of temperature. This functionality represents the fact that micro-organisms die or become dormant at high temperatures. The heat release due to the oxidation reaction is modelled by the usual manner using Arrhenius kinetics. The bifurcation behaviour is investigated for two-dimensional slab geometries to determine the critical sizes of the compost piles.
    Type of Medium: Electronic Resource
    URL: http://www.bepress.com/cppm/vol2/iss2/8
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  • 10
    Electronic Resource
    Electronic Resource
    A MINLP Solution for Pellet Reactor Modeling (2007)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 2 (2007), S. 7 
    Details
    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A fluidized bed reactor for phosphate precipitation and removal from wastewater is modeled according to a two-step procedure. The first modeling phase, based on the development of a thermodynamic model for the computation of phosphate conversion, previously presented elsewhere is not reported here. The second step is related to the reactor modeling in the core of this paper. The pellet reactor is modeled as a reactor network involving a set of elementary cells representing ideal flow patterns. All the potential solutions are imbedded into a superstructure and the modeling problem is expressed as a MINLP problem. The MINLP problem is solved by means of the GAMS package, first for two flow rate values corresponding to two experimental fluidized bed behaviours, and then for the two flow rates considered simultaneously. In each case, the problem consists in finding an output concentration as close as possible to the experimental output concentration. Three objective functions are studied. The results are compared with those of Montastruc et al. (2004) who used a different numerical procedure. Whatever the considered case, the solutions found are structurally simpler than the ones of Montastruc et al. (2004). A major assessment of this study is that the reactor efficiency can easily be deduced, without any precise knowledge of some key parameters such as the density and thickness of the calcium phosphate layer. Finally a last numerical study concerning the superstructure definition shows that too complex a superstructure does not provide significant refinements on the solution.
    Type of Medium: Electronic Resource
    URL: http://www.bepress.com/cppm/vol2/iss3/7
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