DOCSLIB.ORG

6. Energy Balance on Chemical Reactors

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
6. Energy Balance on Chemical Reactors 6. Energy balance on chemical reactors Most of reactions are not carried out isothermally BATCH or CSTR heated (cooled) reactors Inlet tubing Coolant outlet Reaction Mixer mixture Double shell Coolant Outlet Internal inlet tubing heat exchanger The balance of total energy involves: Internal energy mechanical energy (kinetic energy) potential energy R.B.Bird, W.E.Stewart, E.N.Lightfoot : .... Transport Phenomena, 2nd Edition, J.Wiley&Sons, N.Y. 2007 Transformation of various kinds of energy Balance of total energy Input x Output Input x Output of total energy of total energy by convective by molecular flux flux Rate of change of total energy EUEE Work done kin p Work done by molecular by external interactions forces Main reason to study energy balances : assesment of temperature of reacting system (reactor) Application of the 1st law of thermodynamics on the open homogeneous reacting system Rate of work done on surroundings [W] Heat flux [W] E e dV V VR Single phase reacting system eo,e1 – specific total energy of inlet (outlet) streams [J/mol] 3 VR – volume of reaction mixture [m ] dE F e Fe Q W dt oo 11 eeo ,1 molar energies of inlet and outlet streams [J/mol] Rate of work W done by the reacting system on the surroundings consists of: • Flow work of inlet stream(s) VPFVPo o o mo o • Flow work of outlet stream(s) V1 P 1 FV 1m 1 P 1 • Work provided by stirrer Ws dVR • Work done by volume change P dt • Work done by electric, magnetic fields Wf dE dV FeVP FeVPQP R WW dto o mo o1 1 m 1 1 dt s f Neglecting potential and kinetic energies (EU ), we have dU dV F h F h Q PR W W dto mo11 m dt s f hhmo, m1 molar enthalpies of inlet and outlet streams [J/mol] If WWsf0, 0 dU dV F h F h Q P R dto mo11 m dt From enthalpy definition dH dU dP dV dH dP VP R V F h F h Q dt dtR dt dt dtR dt o mo11 m Introducing partial molar enthalpies of species N oo Fo h mo F i H i i1 N F11 hm F i H i i1 We have finally NN dH dP oo VFHFHQR i i i i dt dt ii11 BATCH reactor dH dP VQ dtR dt Enthalpy is a function of temperature, pressure and composition Total heat capacity [J/K] Partial molar enthalpy [J/mol] HHH N dH dT dP dni T P,, n P T n i1 ni jjT,, P n ji HH NN CP dT dP H i dn i m V R c P dT dP H i dn i PP T,, njjii11 T n Molar density [mol/m3 ] Molar heat capacity [J/mol/K] We know that (from thermodynamics) H VR VTVTR R1 p PT Tn, j Pn, j where the coefficient of isobaric expansion is defined as 1 VR p VT R Pn, j and we obtain N dH dT dP dni mc P V R V R1 p T H i dt dt dti1 dt dn Finally by substitution of i in the energy balance of the batch reactor dt NR dT dP N dn dni i VrR ki V, k mc P V R p V R T H i Q dt k1 dt dti1 dt Using definition of the enthalpy of k-th reaction N rHH k ki i i1 we have dT dP NR mc P V R p V R T V R r H k r V, k Q dt dt k1 dP Isobaric reactor ( 0 ) dt dT NR mc P V R V R r H k r V, k Q dt k1 VR f() t we need state equation ! Homework 8: Energy balance of ideal gas isobaric batch reactor dV Isochoric reactor ( R 0 ) dt NR dT p mV R c V V R r H k T V kr V, k Q dt k1 T Pf ()t the coefficient of isobaric expansion the coefficient of isothermal compressibility 11VVRR pT VTVP RR P, nj T the volume variation due to k-th chemical reaction N V VVVk ki i, where i is the partial molar volume of species i i1 ni T,, p n ji the specific heat capacity at constant volume 2 PP VR p CVPPR C T C TV pC P TV R TTT Vn, j Pn, j Vn, j T Variation of the pressure can be derived from total differential of volume N VR dT dni Vi N TPn, dti1 dt dPj p dT 1 dni Vi dtVR dt Vi1 dt TRT P Tn, j Homework 9: Energy balance of ideal gas isochoric batch reactor dV R 0 Summary of energydt balance of BATCH reactor NR dT p mV R c V V R r H k T V kr V, k Q dt k1 T Pf ()t dP 0 dt dT NR mc P V R V R r H k r V, k Q 0,cc dt NR If p p V dT k1 liquid (condensed) systems mc P V R V R r H k r V, k Q Rate of change Rate of heat generation Rate of heat of reactiondt mixture k 1by chemical reactions loss (input) enthalpy Heat fluxV : f() t RQSTT H ( e ) the overall (global) heat transfer coefficient [W.m21 .K ] 2 SH the heat exchange area [m ] Te temperature of external cooling (heating) fluid Limiting cases dT NR Isothermal mc P V R0 V R r H k r V, k Q dt reactor k1 Adiabatic dT NR Q0 c V V H r reactor m p R R r k V, k dt k1 Example Adiabatic reactor with 1 reaction, constant heat capacities Energy balance on adiabatic BATCH reactor dT c V V H r m p Rdt R r V Molar balance of key component dc dX jj cro dtj dt j V N mV R n, c p y i c pi i1 NNN Vcnyc nc noo i nXc m R p i pi i pi i j j pi i1 i 1 i 1 j NNNoo oonj X j n j X j ni c pi i c pi n i c pi c p i1 j i 1 i 1 j Assuming that cpi const c p const yo H() T X TT j r o j TX o N o j j oo vj y i c pi y j c p X j i1 yo H() T j r o the adiabatice rise of temperature j N oo vj y i c pi y j c p X j i1 Trajectories of T(t) and Xj(t) Xj = 1 Exothermal reaction T(t) Xj(t) r H 0 Xj(t) o yj r H() T o j N oo vj y i c pi y j c p X j T(t) i1 To t Homework 10 The reversible reaction A1 + A2 A3 is carried out adiabatically in a constant-volume BATCH reactor. The kinetic equation is r k c1/2 c 1/2 k c fb1 2 3 31 k f (373 K)=2x10 s E1 100 kJ/mol 51 kb (373 K)=3x10 s E2 150 kJ/mol Initial conditions and thermodynamic data cco 0.1 mol/dm3 25 J/mol/K 11p o 3 cc220.125 mol/dm p 25 J/mol/K oo rpH298 40 kJ/mol c 3 40 J/mol/K T = 373K Calculate X1(t),T(t). Example Acetic anhydride reacts with water (CH3CO)2O + H2O 2CH3COOH in a BATCH reactor of constant volume of 100 l. Kinetics of reaction is given by 46500 r2.14 107 eRT c mol.m 3 .min 1 V 1 Data o -1 -1 -1 1 3 c1 0.3 mol.l , cpM 3.8 kJ.kg .K , H r 209kJ.mol , =1070 kg.m 1 oocpi .SH =200W.K T e T 300 K, c p 0, c pM w i c pMi , c pMi i M i wco initial mass fractions, - mass heat capacities (kJ.kg-1 .K -1 ),M - molar weight (kg.mol 1 ) i pMi i RK 8.31446 J.mol11 . In neglecting variation of heat capacities with temperature, calculate T(t) and X1(t) for an non-adiabatic and adiabatic case. By numerical integration we get dT 1 46500 0.1 209E3 2.14E7xexp - 300 (1 X1 ) 200 (300-T) dt(1070 3.8E3 0.1) (8.31446 T ) dX1 46500 2.14E7 exp - (1 X1 ) dt(8.31446 T ) 316 1.20 T [K] 314 1.00 X1 312 0.80 310 0.60 308 0.40 306 0.20 304 0.00 0 10 20 30 40 50 60 t [min] Continuous (perfectly) stirred reactor (CSTR) Energy balance on CSTR NN dH dP oo VFHFHQR i i i i dt dt ii11 Total differential of enthalpy N dH dT dP dni mc P V R V R1 p T H i dt dt dti1 dt NN dP oo VFHFHQR i i i i dt ii11 Molar balance on CSTR NR dni o Fi F i V R ki r V, k , i 1, N dt k1 We get N dT dP N NR rHH kc V ki i TV H Fo F V r Enthalpy mPRdt pR dt ii iR kiVk, i1 ik11change for NN oo k-th reaction FHFHQi i i i ii11 dT dP NR mc P V R V R p T V R r H k r V, k dt dt k1 N oo FHHQi i i i1 dP 0 dt The CSTR usually works at constant pressure (no pressure drop) NR N dT oo QSTT Tm() mPRc V V R rkVk H r, + F ii H H i Q dt ki11 Steady state dT dn i 0 dt dt NR N oo VR r H k r V, k + F i H i H i Q 0 ki11 Assuming ideal mixture, i.e.
Load more

Recommended publications
  • Mixing Time—Experimental Determination and Applications to the Modelling of Crystallisation Phenomena
    Preprints (www.preprints.org) | NOT PEER-REVIEWED | Posted: 3 November 2016 doi:10.20944/preprints201611.0022.v1 Article Mixing Time—Experimental Determination and Applications to the Modelling of Crystallisation Phenomena Dragan D. Nikolić *, Giuseppe Cogoni and Patrick J. Frawley Synthesis and Solid State Pharmaceutical Centre, University of Limerick, Limerick, Ireland; [email protected] (G.C.); [email protected] (P.J.F.) * Correspondance: [email protected] Abstract: Performing optimisation and scale-up studies of crystallisation systems requires accurate and computationally efficient mathematical models. The assumption of the ideal mixing conditions in batch reactors typically produce inaccurate results while the computational expense of CFD models is still prohibitively high. Therefore, in this work, a new intermediary approach is proposed that takes into account the non-ideal mixing conditions in the reactor and requires less computational resources than full CFD simulations. Starting with the Danckwerts concept of the intensity of segregation, an analogy between its application to chemical reactions and the kinetics of the crystallisation phenomena (such as nucleation and growth) has been made. As a result, the modified kinetics expressions have been derived which incorporate the effect of non-idealities present in stirred reactors. This way, based on the experimental measurements of the mixing time using the Laser Induced Fluorescence (LIF) technique, computationally more efficient mathematical models can be developed in two ways: (1) the accurate semi-empirical correlations are available for standard mixing configurations with the most often used types of impellers, (2) CFD simulations can be utilised for estimation of the mixing time; in this case it is necessary to simulate only the mixing process.
    [Show full text]
  • Temperature Simulation and Heat Exchange in a Batch Reactor Using Ansys Fluent
    Graduate Theses, Dissertations, and Problem Reports 2018 Temperature Simulation and Heat Exchange in a Batch Reactor Using Ansys Fluent Rahul Kooragayala Follow this and additional works at: https://researchrepository.wvu.edu/etd Recommended Citation Kooragayala, Rahul, "Temperature Simulation and Heat Exchange in a Batch Reactor Using Ansys Fluent" (2018). Graduate Theses, Dissertations, and Problem Reports. 6006. https://researchrepository.wvu.edu/etd/6006 This Thesis is protected by copyright and/or related rights. It has been brought to you by the The Research Repository @ WVU with permission from the rights-holder(s). You are free to use this Thesis in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you must obtain permission from the rights-holder(s) directly, unless additional rights are indicated by a Creative Commons license in the record and/ or on the work itself. This Thesis has been accepted for inclusion in WVU Graduate Theses, Dissertations, and Problem Reports collection by an authorized administrator of The Research Repository @ WVU. For more information, please contact [email protected]. Temperature simulation and heat exchange in a batch reactor using Ansys Fluent Rahul Kooragayala Thesis submitted to the Benjamin M. Statler College of Engineering and Mineral Resources at West Virginia University in partial fulfillment of the requirements for the degree of Master of Science in Mechanical Engineering Cosmin Dumitrescu, Ph.D., Chair Hailin Li, Ph.D. Vyacheslav Akkerman, Ph.D. Department of Mechanical and Aerospace Engineering Morgantown, West Virginia 2018 Keywords: Ansys Fluent, batch reactor, heat transfer, simulation, water vaporization Copyright 2018 Rahul Kooragayala Abstract Temperature simulation and heat exchange in a batch reactor using Ansys Fluent Rahul Kooragayala Internal combustion (IC) engines are the main power source for on-road and off-road vehicles.
    [Show full text]
  • CHAPTER 9 Nonisotbermal Reactors 287
    ________---""C"'--H APT E RL-- 9""'---- Nonisothermal Reactors 9.1 I The Nature of the Problem In Chapter 3, the isothennal material balances for various ideal reactors were derived (see Table 3.5.1 for a summary). Although isothermal conditions are most useful for the measurement of kinetic data, real reactor operation is nonnally nonisothennal. Within the limits of heat exchange, the reactor can operate isothennally (maximum heat exchange) or adiabatically (no heat exchange); recall the limits of reactor be­ havior given in Table 3.1.1. Between these bounds of heat transfer lies the most com­ mon fonn of reactor operation-the nonisothermal regime (some extent of heat ex­ change). The three types of reactor operations yield different temperature profiles within the reactor and are illustrated in Figure 9.1.1 for an exothennic reaction. If a reactor is operated at nonisothennal or adiabatic conditions then the ma­ terial balance equation must be written with the temperature, T, as a variable. For example with the PFR, the material balance becomes: vir(Fi,T) (9.1.1) Since the reaction rate expression now contains the independent variable T, the material balance cannot be solved alone. The solution of the material balance equation is only possible by the simult<meous solution of the energy balance. Thus, for nonisothennal re~ actor descriptions, an energy balance must accompany the material balance. 9.2 I Energy Balances Consider a generalized tlow reactor as illustrated in Figure 9.2.1. Applying the first law of thennodynamics to the reactor shown in Figure 9.2.1, the following is obtained: (9.2.1) CHAPTER 9 Nonisotbermal Reactors 287 ~ ---·I PF_R ..
    [Show full text]
  • Reactor Design
    Reactor Design Andrew Rosen May 11, 2014 Contents 1 Mole Balances 3 1.1 The Mole Balance . 3 1.2 Batch Reactor . 3 1.3 Continuous-Flow Reactors . 4 1.3.1 Continuous-Stirred Tank Reactor (CSTR) . 4 1.3.2 Packed-Flow Reactor (Tubular) . 4 1.3.3 Packed-Bed Reactor (Tubular) . 4 2 Conversion and Reactor Sizing 5 2.1 Batch Reactor Design Equations . 5 2.2 Design Equations for Flow Reactors . 5 2.2.1 The Molar Flow Rate . 5 2.2.2 CSTR Design Equation . 5 2.2.3 PFR Design Equation . 6 2.3 Sizing CSTRs and PFRs . 6 2.4 Reactors in Series . 7 2.5 Space Time and Space Velocity . 7 3 Rate Laws and Stoichiometry 7 3.1 Rate Laws . 7 3.2 The Reaction Order and the Rate Law . 8 3.3 The Reaction Rate Constant . 8 3.4 Batch Systems . 9 3.5 Flow Systems . 9 4 Isothermal Reactor Design 12 4.1 Design Structure for Isothermal Reactors . 12 4.2 Scale-Up of Liquid-Phase Batch Reactor Data to the Design of a CSTR . 13 4.3 Design of Continuous Stirred Tank Reactors . 13 4.3.1 A Single, First-Order CSTR . 13 4.3.2 CSTRs in Series (First-Order) . 13 4.3.3 CSTRs in Parallel . 14 4.3.4 A Second-Order Reaction in a CSTR . 15 4.4 Tubular Reactors . 15 4.5 Pressure Drop in Reactors . 15 4.5.1 Ergun Equation . 15 4.5.2 PBR . 15 4.5.3 PFR . 16 4.6 Unsteady-State Operation of Stirred Reactors .
    [Show full text]
  • Heat Exchanger/Reactors (HEX Reactors): Concepts, Technologies: State-Of-The-Art
    Review Heat exchanger/reactors (HEX reactors): Concepts, technologies: State-of-the-art Z. Anxionnaz a,b, M. Cabassud a,∗, C. Gourdon a, P. Tochon b a Laboratoire de Génie Chimique, UMR 5503 CNRS/INPT/UPS, 5 rue P. Talabot, BP 1301, 31106 Toulouse Cedex 1, France b Atomic Energy Commission-GRETh, 17 avenue des Martyrs, F-38054 Grenoble Cedex 9, France abstract Process intensification is a chemical engineering field which has truly emerged in the past few years and is currently rapidly growing. It consists in looking for safer operating conditions, lower waste in terms of costs and energy and higher productivity; and a way to reach such objectives is to develop multifunctional devices such as heat exchanger/reactors for instance. This review is focused on the latter and makes a point on heat exchanger/reactors. After a brief presentation of requirements due to transposition from batch to continuous apparatuses, Keywords: heat exchangers/reactors at industrial or pilot scales and their applications are described. Process intensification Heat exchanger reactor State-of-the-art Technology Continuous reactor Contents 1. Introduction........................................................................................................................................ 2030 2. Transposition from batch to continuous heat-exchanger/reactor ................................................................................ 2030 2.1. Thermal intensification....................................................................................................................
    [Show full text]
  • A Simulation Study of Heat Transfer in Polymerization Reactors
    A SIMULATION STUDY OF HEAT TRANSFER IN POLYMERIZATION REACTORS Mohamed El-Helw*, Mohamed El-Seuofy, Abd-El-Hamid Attia Mechanical Engineering Department, Faculty of Engineering, Alexandria University, Egypt Corresponding Author Email: [email protected], [email protected] Abstract In this paper, the heat transfer in polymer reactors has been investigated. The study of various methods of heat transfer in jacketed agitated vessels and the impact of altering different agitators on the heat transfer are indicated. A computer program is developed to calculate the heat transfer parameters and the heat duty required for each case. The PVC polymer reactor in the Egyptian Petrochemical Company is chosen as a case study. This reactor is modeled by Microsoft Excel and simulated by a VisiMix simulation program version turbulent SV. In addition, the chemical reaction is modeled by Aspen HYSYS V8, and eventually the modeling results are validated with the actual design data. Meanwhile, a comparison between various heat transfer methods is generated to set the preferable design and the topmost impeller for high heat transfer conditions. Furthermore, this preferable design is adopted to analyze the alteration on its performance. The result indicates that, the retreating turbine impeller is the best for a high inside heat transfer coefficient and the half coil jacket is the best for a maximum outside heat transfer coefficient. The performance investigation shows that this design is preferable for the optimum recommended flow velocity in the jacket of v=2.3m/s, as the outside heat transfer coefficient would increase by 31.47%. Finally, the new approach which is released by Vinnolit Uhde Company is applied and its result show that the heat duty would increase by 32% due to the installation of an inner cooler inside the reactor wall, which represents a significant stride for a high performance polymer reactor.
    [Show full text]
  • Chemical Reactor Design and Control
    CHEMICAL REACTOR DESIGN AND CONTROL CHEMICAL REACTOR DESIGN AND CONTROL WILLIAM L. LUYBEN Lehigh University AlChE R Copyright # 2007 by John Wiley & Sons, Inc. All rights reserved. Published by John Wiley & Sons, Inc., Hoboken, New Jersey Published simultaneously in Canada. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, scanning, or otherwise, except as permitted under Section 107 or 108 of the 1976 United States Copyright Act, without either the prior written permission of the Publisher, or authorization through payment of the appropriate per-copy fee to the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923, 978-750-8400, fax 978-750-4470, or on the web at www.copyright.com. Requests to the Publisher for permission should be addressed to the Permissions Department, John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, 201-748-6011, fax 201-748-6008, or online at http://www.wiley.com/go/permission. Limit of Liability/Disclaimer of Warranty: While the publisher and author have used their best efforts in preparing this book, they make no representations or warranties with respect to the accuracy or completeness of the contents of this book and specifically disclaim any implied warranties of merchantability or fitness for a particular purpose. No warranty may be created or extended by sales representatives or written sales materials. The advice and strategies contained herein may not be suitable for your situation. You should consult with a professional where appropriate. Neither the publisher nor author shall be liable for any loss of profit or any other commercial damages, including but not limited to special, incidental, consequential, or other damages.
    [Show full text]
  • Turbulent Mixing and Chemical Reaction in Baffled Stirred Tank Reactors
    Copyright Warning & Restrictions The copyright law of the United States (Title 17, United States Code) governs the making of photocopies or other reproductions of copyrighted material. Under certain conditions specified in the law, libraries and archives are authorized to furnish a photocopy or other reproduction. One of these specified conditions is that the photocopy or reproduction is not to be “used for any purpose other than private study, scholarship, or research.” If a, user makes a request for, or later uses, a photocopy or reproduction for purposes in excess of “fair use” that user may be liable for copyright infringement, This institution reserves the right to refuse to accept a copying order if, in its judgment, fulfillment of the order would involve violation of copyright law. Please Note: The author retains the copyright while the New Jersey Institute of Technology reserves the right to distribute this thesis or dissertation Printing note: If you do not wish to print this page, then select “Pages from: first page # to: last page #” on the print dialog screen The Van Houten library has removed some of the personal information and all signatures from the approval page and biographical sketches of theses and dissertations in order to protect the identity of NJIT graduates and faculty. ABSTRACT TURBULENT MIXING AND CHEMICAL REACTION IN BAFFLED STIRRED TANK REACTORS: A COMPARISON BETWEEN EXPERIMENTS AND A NOVEL MICROMIXING-BASED COMPUTATIONAL FLUID DYNAMICS MODEL by Otute Akiti The optimization of reaction processes to maximize the yield of a desired product while minimizing the formation of undesired by-products is one of the most important steps in process development for drug manufacturing or fine chemical production.
    [Show full text]
  • UK Chemcad Seminar - November 2000
    UK ChemCAD Seminar - November 2000 PROCESS MODELLING AND CONTROL OF BATCH REACTORS IN THE FINE CHEMICALS INDUSTRY by John E. Edwards [email protected] Download available from www.pidesign.co.uk P & I Design Ltd MNL029 05/01 2 Reed Street, Thornaby, UK, TS17 7AF Page 1 of 23 Tel: 00 44 (1642) 617444 Fax: 00 44 (1642) 616447 www.pidesign.co.uk Process Modelling and Control of Batch Reactors in the Fine Chemicals Industry Contents 1.0 Introduction 2.0 Process Characteristics 2.1 Reaction Chemistry 2.2 Process Engineering Constraints 3.0 Control Configurations 3.1 Direct Jacket Heat/Cool 3.2 Direct Jacket Cool/Indirect Heat 3.3 Indirect Jacket Heat/Cool 3.4 Instrumentation and Control 4.0 Performance Predictions Appendices I Summary of Heat Transfer in Glass Lined Reactors (Acknowledgements to Pfaudler Reactor Systems) II Control Valve Characteristic Selection III Control Loop Tuning IV ChemCAD User Guidance Notes Figures 1. Reactor Control Systems 2. Indirect Jacket Heating Model 3. Indirect Jacket Cooling Model 4. Condenser Control System 5. Condenser Control System Model 6. Control Valve Characteristics 7. Controller & Control Valve Action (ChemCAD) 8. Reactor Thermal Rating Spreadsheet 9. Batch Reactor Plot Options Graphs 1. 1600L Hastelloy Reactor Heat Up 2. 1600L Reactor Boil Up/Emissions 3. 1600L Hastelloy Reactor Cool Down 4. Condenser Model Controller Tuning Tu 5. Condenser Model Controller Tuning MNL029 05/01 Page 2 of 23 Process Modelling and Control of Batch Reactors in the Fine Chemicals Industry References 1. F.G. Shinskey, “Process Control Systems”, McGraw-Hill, 1967. 2. J.
    [Show full text]
  • Control Valve Sourcebook — Chemical Process Overview Reactor
    Control Valve Sourcebook — Chemical Process Overview Reactor Topic Page I How it Operates 2 II Where Reactors Are Used 3 III Reactor Application Review 4 Reactor Plug Flow Reactor (PFR) Reactor This reactor is primarily used for gas-phase reactions. It is modeled and designed after a “plug flow profile.” The I. How It Operates conversion of chemicals is also reliant of the reactor volume. This reactor has tubes that the feed (gases and/or liquids) A chemical reactor is a vessel designed to contain reactions travel through at high velocity. This helps with mixing and in order to produce a desired product. Listed below are the causing the feed to take a long path through the reactor. most common types of reactors and methods of operation. Hence, more time for the feed to be converted into desired Types of reactors: products. Refer to Figure 2 for a representation of PFR. Continuous stirred tank Plug flow reactor Packaged bed reactor (fixed or fluidized) Methods of operations: Batch Continuous Semi-continuous Types of Reactors Continuous Stirred Tank (CSTR) The CSTR reactor is primarily used for liquid-phase reactions. As the name suggests, it is stirring to attempt perfect mixing. The conversion of the chemical is dependent on the E1706 volume of the reactor. Figure 1 shows a representation of a CSTR. Figure 2. Representation of a PFR Each reactor will have a fixed volume which also means it will have a fixed residence time. Knowing these two values feed rate can be controlled accurately. Packed Bed Reactor (PBR) REACTANT 1 A PBR can be either fluidized or fixed bed and is primarily REACTANT 2 used for gas-phase reactions.
    [Show full text]
  • Reactor Design-General Principles
    CHAPTER 1 Reactor Design-General Principles 1.1. BASIC OBJECTIVES IN DESIGN OF A REACTOR In chemical engineering physical operations such as fluid flow, heat transfer, mass transfer and separation processes play a very large part; these have been discussed in Volumes 1 and 2. In any manufacturing process where there is a chemical change taking place, however, the chemical reactor is at the heart of the plant. In size and appearance it may often seem to be one of the least impressive items of equipment, but its demands and performance are usually the most important factors in the design of the whole plant. When a new chemical process is being developed, at least some indication of the performance of the reactor is needed before any economic assessment of the project as a whole can be made. As the project develops and its economic viability becomes established, so further work is carried out on the various chemical engineering operations involved. Thus, when the stage of actually designing the reactor in detail has been reached, the project as a whole will already have acquired a fairly definite form. Among the major decisions which will have been taken is the rate of production of the desired product. This will have been determined from a market forecast of the demand for the product in relation to its estimated selling price. The reactants to be used to make the product and their chemical purity will have been established. The basic chemistry of the process will almost certainly have been in- vestigated, and information about the composition of the products from the reaction, including any byproducts, should be available.
    [Show full text]
  • CHEE 321: Chemical Reaction Engineering
    CHEE 321: Chemical Reaction Engineering Module 5: Multiple Reactions (Chapter 6, Fogler) Course (Content) Organization Isothermal, Ideal Reactor (Single Reaction) Design Output Mole Balance Rate Law Design Algorithm (Module-1) (Module-2) (Module-3) • Reactor Volume In – Out + Con = Acc n 1. GMBE, 2. Rate Law • Reaction Time (rA) = kCA FA,in-FA,out+(rA)V = dCA/dt 3. Stoich 4.Combine • Rate Constant Analysis of Rate law (Module-4) Kinetics: How to obtain k and rxn order • Conversion Multiple Reactions • Product Composition (Module-5) Selectivity, Yield Non-Isothermal Reactor Design Output (Module-6) • Energy Balance • Temperature Profile dT/dz = ? • Heat Transfer Rate • Heat Removal • Equilibrium Reactions • Heating Requirement T -T =? • Multiple Steady State in out Topics to be covered in this Module • Types of multiple reactions • Introduction to selectivity and yield • Qualitative Analyses (Parallel and Series Reactions) – Maximizing the reactor operation for single reactant systems – Maximizing the reactor operation for two reactant systems • Algorithm for Reactor Design of Multiple Reactions – Mole Balance – Net Rates of Reactions – Stoichiometry Multiple Reactions Types of Multiple Reactions 1. Series Reactions ⎯ABC → ⎯k1 2 k⎯ → ⎯ Use molar flow rates and concentrations; 2. Parallel Reactions DO NOTuse conversion! ⎯ABk1 → ⎯ ⎯ACk2 → ⎯ 3. ParallelComplex Reactions: Series and ⎯ABC →k1 ⎯ + +ACD ⎯k2 → ⎯ Cannot use stoichiometric tables to relate 4. Independent change in CB to change in CA ⎯ACk1 → ⎯ ⎯B k2 →D ⎯ Selectivity and Yield Desired Reaction: Instantaneous Global kD A ⎯→⎯ D rD ~ FD Selectivity SDU = SDU = r F Undesired Reaction: U U k U rD A⎯⎯→U FNDD Yield YD = YD == kU2 −rA DU⎯⎯→ FFNNA00−−AAA • What should be the criterion for designing the reactor ? • Is it necessary that reactor operates such that minimum amount of undesired products are formed ? D S Total Cost E P Reactor D A A R Cost System U A T O R U Reactant Conversion Instantaneous vs.
    [Show full text]