Composting kinetics for mixture of poultry manure and wheat straw based on volatile solids content

The aim of this study was to determine the composting kinetics for mixture of poultry manure and wheat straw based on the volatile solids content. Experimental data was fitted with the first-order and the nth-order kinetic model. The nth-order kinetic model showed better prediction performance than the firstorder kinetic model. For the first-order kinetic model, maximum and mean differences between experimental and simulation results for the content of volatile solids were 5.43% and 3.00%, for the first reactor, and 4.68% and 2.12% for the second reactor, respectively, for the nth-order kinetic model, maximum and mean differences were 4.92% and 1.68%, for the first reactor, and 4.09% and 1.42% for the second reactor, respectively. Keywords: Composting kinetics, poultry manure, wheat straw, volatile solids content. DOI: http://dx.doi.org/10.7251/JEPM1709036

Minimization of Utilities Consumption in a Distillation Column with and without Heat Integration for Separation of a Binary System of Acetone-Methanol

U ovom radu razvijeni su matematički modeli za destilacijsku kolonu s toplinskom integracijom i bez toplinske integracije. Simulacija matematičkih modela primijenjena je za određivanje potrošnje energije u destilacijskoj koloni za razdvajanje binarnog sustava acetona i metanola. Predloženi modeli određuju vrijednosti procesnih varijabli s ciljem utvrđivanja minimalne potrošnje pogonskih sredstava. Prikazana je usporedba rezultata toplinski integrirane destilacijske kolone s rezultatima neintegrirane destilacijske kolone. Rezultati su pokazali da se ušteda energije može postići primjenom toplinske integracije. Predloženi modeli mogu se primijeniti za projektiranje novih ili preuređenje postojećih destilacijskih kolona za razdvajanje binarnih smjesa. Ovo djelo je dano na korištenje pod licencom Creative Commons Imenovanje 4.0 međunarodna.In this work, mathematical models for a distillation column with and without heat integration have been developed. Simulation based on the developed mathematical models was used to determine the energy consumption in the distillation column for separation of a binary system of acetone and methanol. The proposed models determine the values of process variables in order to obtain the minimum utilities consumption. The comparison of results of the heat-integrated distillation column with those of the non-integrated distillation column are presented. The results show that energy savings could be achieved using heat integration. The proposed models may be applied to the design of new or redesign of existing distillation columns for separation of binary mixtures. This work is licensed under a Creative Commons Attribution 4.0 International License

Application of validated mathematical model of composting process for study the effect of air flow rate on process performance

The objectives of this study were to develop and validate the mathematical model (kinetic and reactor model) of composting process, as well to used validated model in order investigate the effects of the air flow rate on organic matter conversion, carbon dioxide concentration and mixture temperature. The mathematical model incorporated two microbial populations that metabolized composting material which was split into two different fractions according to its degradability (easily-degradable and hardly-degradable). Comparisons of simulation and experimental results for five dynamic state variables demonstrated that the model has very good predictions of the composting process. Simulations with validated model showed that among three dynamic state variables (organic matter conversion, carbon dioxide concentration, mixture temperature), carbon dioxide concentration is the most sensitive while organic matter conversion is the least sensitive to the change of air flow rate. Keywords: air flow rate, composting, kinetic model, reactor model, simulation. DOI: http://dx.doi.org/10.7251/JEPM1709062

Analysis, Synthesis and Optimization of Multiple-Effect Evaporation Systems using Mathematical Programming

Evaporation processes are used within the process industries in order to produce concentrated products by evaporating part of water from different feeds-diluted water solutions. Concentrated products can represent final products (fruit and vegetable juices) or intermediate products in cases that crystalized (salt, sugar) or dried (milk powder) final products should be produced. Large amounts of steam and cooling water are consumed in these processes. In order to reduce energy and water consumption within evaporation processes different systems can be applied, namely, multiple-effect evaporation, vapor recompression (thermal and mechanical) or their combinations. Additionally, these processes can be integrated with other process subsystems in order to achieve improved energy and water integration. To address these issues different computer-aided tools have been proposed. However, most studies have focused on analysis and simulation of evaporation processes. Some of the initial studies [1, 2] considered the synthesis of evaporation processes in order to develop tools for computing the minimum utility use for a multiple-effect evaporation system, which was heat-integrated with process hot and cold streams. These studies were based on a modified grand composite curve and heat-path diagram. Also, the focus of the recent works have been on multiple-effect evaporation systems [3] and their energy integration with the background processes in order to minimize the energy consumption within the overall system [4]. These studies have motivated us to further expand research in this direction, by applying mathematical programming approach for the analysis of existing and the design of new evaporation systems as well as their heat integration with other process subsystems or process streams. The main goal of this paper is to develop models based on mathematical programming that can be applied for the analysis, synthesis and optimization of multiple-effect evaporation systems. The proposed models will be developed in General Algebraic Modeling System (GAMS). The developed models will enable examination of different scenarios of multiple-effect evaporation in order to address the analysis of existing, retrofit and/or design new evaporation process. Within the proposed framework, a network consisting of a multiple-effect evaporation system and heat exchanger network will be investigated in order to achieve the improved heat integration within the overall system. Two strategies will be considered to achieve this task, namely, sequential and simultaneous. The developed models will be tested on several examples, and also applied to different feed streams. New results are expected to be obtained within this field. Keywords: multiple-effect evaporation, analysis, synthesis, optimization, mathematical programming. Acknowledgment The authors are grateful to the Swiss National Science Foundation (SNSF) and the Swiss Agency for Development and Cooperation (SDC) for providing financial support within the SCOPES 2013â??2016 (Scientific Co-operation between Eastern Europe and Switzerland) joint research project (CAPEâ??EWWR: IZ73Z0_152622/1). References: [1] Hillenbrand JJB, Westerberg AW. The synthesis of multiple-effect evaporator systems using minimum utility insightsâ??I. A cascaded heat representation. Computers & Chemical Engineering. 1988;12:611. [2] Westerberg AW, Hillenbrand JJB. The synthesis of multiple-effect evaporator systems using minimum utility insightsâ??II. liquid flowpattern selection. Computers & Chemical Engineering. 1988;12:625. [3] Khanam S, Mohanty B. Energy reduction schemes for multiple effect evaporator systems. Applied Energy. 2010;87:1102. [4] Sharan P, Bandyopadhyay S. Energy Integration of Multiple Effect Evaporators with Background Process and Appropriate Temperature Selection. Industrial & Engineering Chemistry Research. 2016;55:1630

Analiza isparavanja i kristalizacije kalijeva nitrata iz vodene otopine u dvostupnjevitom isparivačkom sustavu i vakuumskom kristalizatoru

U ovom radu prikazana je računalna analiza razdvajanja soli iz dvokomponentnog elektrolitskog sustava. Elektrolitski sustav KNO3-H2O primijenjen je kao “case study” za prikazivanje analize procesa isparavanja i kristalizacije. Sljedeći procesi uzeti su u obzir: dvostupnjeviti isparivački sustav i vakuumski kristalizator s adijabatskim hlađenjem. Razvijen je matematički model dvostupnjevitog isparivačkog sustava i vakuumskog kristalizatora. Matematički model sastoji se od algebarskih jednadžbi. Predloženi model razvijen je u programu Microsoft Excel s VBA (Visual Basic for Applications). Razvijeni model omogućava analizu postojećeg ili dizajniranje novog procesa isparavanja i kristalizacije. Razvijeni model može biti primijenjen na bilo koji dvokomponentni elektrolitski sustav, ali zahtijeva unošenje fizikalno-kemijskih svojstava odgovarajućeg elektrolitskog sustava