Computer-aided chemical engineering 

About: Computer-aided chemical engineering is an academic journal. The journal publishes majorly in the area(s): Process (engineering) & Process design. It has an ISSN identifier of 1570-7946. Over the lifetime, 5779 publications have been published receiving 25657 citations.

EMSO: A new environment for modelling, simulation and optimisation

Abstract: A new tool, named EMSO (Environment for modelling, Simulation and Optimisation), for modelling, simulation and optimisation of general process dynamic systems is presented. In this tool the consistency of measurement units, system solvability and initial conditions consistency are automatically checked. The solvability test is carried out by an index reduction method which reduces the index of the resulting system of differential-algebraic equations (DAE) to zero by adding new variables and equations when necessary. The index reduction requires time derivatives of the original equations that are provided by a built-in symbolic differentiation system. The partial derivatives required during the initialisation and integration are generated by a built-in automatic differentiation system. For the description of processes a new object-oriented modelling language was developed. The extensive usage of the object-oriented paradigm in the proposed tool leads to a system naturally CAPE-OPEN which combined with the automatic and symbolic differentiation and index reduction forms a software with several enhancements, when compared with the popular ones.

Nonlinear Dynamic Process Monitoring Using Canonical Variate Analysis and Kernel Density Estimations

Abstract: Amongst process monitoring techniques the Principal Component Analysis (PCA) and the Partial Least Squares Regression Analysis (PLS) assume that the observations at different times are independent. However, for most industrial processes, these assumptions are invalid because of their dynamic features. For dynamic processes, the Canonical Variate Analysis (CVA) based approach is more appropriate than the PCA and the PLS based approaches. The CVA model is linear and control limits associated with the CVA are traditionally derived based on the Gaussian assumption. However, most industrial processes are non-linear and the Gaussian assumption is invalid for such processes so that techniques based on this assumption may not be able to correctly identify underline faults. In this work, a new monitoring technique using the CVA with control limits derived from the estimated probability density function through kernel density estimation (KDE) is proposed and applied to the Tennessee Eastman Process Plant. The proposed CVA with KDE approach is able to significantly improve the monitoring performance compared to other methods mentioned above.

New General Continuous-Time State−Task Network Formulation for Short-Term Scheduling of Multipurpose Batch Plants

Abstract: A new continuous-time MILP model for the short-term scheduling of multipurpose batch plants is presented. The proposed model relies on the state−task network (STN) approach and addresses the general problem of batch scheduling, accounting for resource (utility) constraints, variable batch sizes and processing times, various storage policies (UIS, FIS, NIS, ZW), batch mixing/splitting, and sequence-dependent changeover times. The key features of the proposed model are the following: (a) a continuous-time representation is used, common for all units; (b) assignment constraints are expressed using binary variables that are defined only for tasks, not for units; (c) start times of tasks are eliminated, so that time-matching constraints are used only for the finish times of tasks; and (d) a new class of valid inequalities that improves the LP relaxation is added to the MILP formulation. Compared to other general continuous time STN formulations, the proposed model is faster. Compared to event-driven formulati...

BzzMath: Library Overview and Recent Advances in Numerical Methods

Abstract: This paper gives an overview of the numerical methods included in BzzMath library. The library is written in C++, exploits the features of object-oriented programming, and is free for non-commercial applications at www.chem.polimi.it/homes/gbuzzi .

Simple Equation for Suitability of Heat Pump Use in Distillation

Abstract: A distillation column can be considered as a heat engine that produces separation instead of work. The heat is provided in the reboiler and collected degraded at a lower temperature at the condenser. The energy collected at low temperature at the top of the column can be upgraded back to higher temperatures by means of a heat pump and reused to heat a lower column stage.This can bring saving in terms of the overall amount of energy required. However, the energy required to increase the pressure is of higher quality and price than hot services. The aim of the present paper is to provide an easy way to check, in the early stages of design, when the use of a heat pump can provide a more sustainable distillation process decreasing its energy requirements. After several simplifications, it can be stated that it depends mainly on the efficiency of Carnot. When the efficiency of Carnot is evaluated for the industrial systems where the heat pumps are used, it is concluded that all have Carnot efficiency around 0.1 or lower. Therefore, in the early design of a new distillation column, this criterion is useful to decide when a heat pump is worth to be included in the more rigorous simulations.