Title
Disclaimer
Table of Contents
Abstract
List of Tables
List of Figures
Section 1 - Introduction 1 - 1
Section 2 - Design review, audit of energy and material balance 2 - 1
A. Review of plant design 2 - 1
B. Audit of actual plant operation 2 - 1
C. Data collection during plant operation 2 - 3
Section 3 - Energy saving improvements with minimal capital investements 3 - 1
A. Operating procedure revisions
(1) Reducing the reflux ratio of columns 3 - 1
(2) Lowering product specifications 3 - 3
(3) Lowering pumping costs 3 - 4
(4) Lowering steam usage 3 - 9
(5) Process heaters 3 -11
B. Scheduling shutdowns to maximize energy recovery and profits 3 -13
Section 4 - Energy savingins improvements with capital investements 4 - 1
A. Optimization of heat recovery - heat exchangers 4 - 1
B. Column revisions 4 - 5
(l) Additional or more Efficient trays 4 - 5
(2) Additional column draw 4 - 7
C. Optimization of recovery and use of energy 4 - 7
(1) Introduction 4 - 7
(2) Column Heat Utilization 4 - 9
2.1 Bottoms product 4 -10
2.2 Distillate product 4 -11
2.3 Condenser duty 4 -11
2.4 Reboiler duty 4 -11
2.5 Feed preheating 4 -12
(3) Changing the column's temperature 4 -12
(4) Two-stage condensation 4 -12
(5) Waste heat boilers 4 -13
(6) Multiple effect heat cascading for distillation columns 4 -13
(7) Split tower 4 -15
(8) Interreboilers, intercondensers, and feed preheating 4 -19
(9) Feed preheating 4 -21
(10) Interreboiler 4 -21
(11) Intercoolers and feed precoolers 4 -21
(12) Circulating refluxes 4 -22
D. Use of vapor recompression and heat pumps for distillation 4 -24
(1) Introduction 4 -24
(2) Distillation column's reflux and heat balance 4 -25
(3) Vapor recompression 4 -26
(4) Heat pump 4 -27
(5) Theory behind vapor-recompression and heat pumps 4 -28
5.1 The Carnot cycle 4 -28
5.2 The refrigeration cycle 4 -33
(6) Vapor recompression 4 -37
6.1 Situations 4 -37
6.2 Auxiliary heat transfer equipment 4 -38
6.3 Compressor drives and their energy costs 4 -40
6.4 Insulation of columns using vapor recompression or heat pumps 4 -41
6.5 Vapor recompression for interreboilers, other columns 4 -41
(7) Reasons for conversion of an existing column 4 -42
(8) Conversion of an existing column 4 -43
(9) Advantages of vapor recompression 4 -44
(10) Disadvantages of vapor recompression 4 -46
(11) Advantages and disadvantages of the heat pump 4 -49
(12) Guidelines for considering vapor recompression 4 -50
(13) Procedure for vapor recompression evaluation 4 -51
(14) Example, propane-propylene splitter 4 -54
14.1 Situation statement 4 -54
14.2 Solution 4 -55
(15) Work problem propane-propylene splitter with bottoms vapor recompression 4 -60
E. Improving control of distillation columns 4 -61
F. Reducing heat losses using insulation 4 -64
Section 5 - Economics 5 - 1
A. Definition of economic terms 5 - 2
(1) Profit 5 - 2
(2) Net back 5 - 2
(3) Depreciation 5 - 3
(4) Investment tax credit 5 - 5
(5) Fixed costs 5 - 5
(6) Variable costs 5 - 6
(7) Cash flow 5 - 6
(8) Discounted cash flow 5 - 6
(9) Return on investment (R.O.I.) 5 - 7
B. Concept of investment equivalence to save energy 5 - 8
C. Economic interpretations for energy savings 5 - 9
D. Steam economics 5 -11
E. Cooling water 5 -13
F. Compressed air 5 -14
G. Vacuum pumps and steam ejectors 5 -14
H. Exchangers used for heat recovery 5 -15
I. Conclusion 5 -15
Section 6 - Bibliography with abstracts 6 - 1
Section 7 - Appendices 7 - 1
A. Energy savings checklist - General 7 - 1
B. Process energy checklist 7 - 6
C. References - Technical articles 7 -10
D. Solution to work problem 4-F-15 7 -14