Page 7 - Chemical engineering design

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2.6
Choice of basis for calculations
2.7 Choice of system boundary CONTENTS 37
40
2.8 Number of independent components 40
2.9 Constraints on flows and compositions 41
2.10 General algebraic method 42
2.11 Tie components 44
2.12 Excess reagent 46
2.13 Conversion and yield 47
2.14 Recycle processes 50
2.15 Purge 52
2.16 By-pass 53
2.17 Unsteady-state calculations 54
2.18 General procedure for material-balance problems 56
2.19 References (Further Reading) 57
2.20 Nomenclature 57
2.21 Problems 57
3 Fundamentals of Energy Balances (and Energy Utilisation) 60
3.1 Introduction 60
3.2 Conservation of energy 60
3.3 Forms of energy (per unit mass of material) 61
3.3.1 Potential energy 61
3.3.2 Kinetic energy 61
3.3.3 Internal energy 61
3.3.4 Work 61
3.3.5 Heat 62
3.3.6 Electrical energy 62
3.4 The energy balance 62
3.5 Calculation of specific enthalpy 67
3.6 Mean heat capacities 68
3.7 The effect of pressure on heat capacity 70
3.8 Enthalpy of mixtures 71
3.8.1 Integral heats of solution 72
3.9 Enthalpy-concentration diagrams 73
3.10 Heats of reaction 75
3.10.1 Effect of pressure on heats of reaction 77
3.11 Standard heats of formation 79
3.12 Heats of combustion 80
3.13 Compression and expansion of gases 81
3.13.1 Mollier diagrams 82
3.13.2 Polytropic compression and expansion 84
3.13.3 Multistage compressors 90
3.13.4 Electrical drives 93
3.14 Energy balance calculations 93
3.15 Unsteady state energy balances 99
3.16 Energy recovery 101
3.16.1 Heat exchange 101
3.16.2 Heat-exchanger networks 101
3.16.3 Waste-heat boilers 102
3.16.4 High-temperature reactors 103
3.16.5 Low-grade fuels 105
3.16.6 High-pressure process streams 107
3.16.7 Heat pumps 110
3.17 Process integration and pinch technology 111
3.17.1 Pinch technology 111
3.17.2 The problem table method 115
3.17.3 The heat exchanger network 117
3.17.4 Minimum number of exchangers 121
3.17.5 Threshold problems 123