CHLORINE-ADVANCED COMMERCIAL CHLOR-ALKALI TECHNOLOGY (December 2012)

Abstract Process Economics Program Report 61E CHLORINE-ADVANCED COMMERCIAL CHLOR-ALKALI TECHNOLOGY (December 2012)

Chlorine and caustic soda represent one of the largest volume chemical segments. Worldwide chlorine demand was 61 million tons in 2011; caustic soda demand was 73 million tons. The chlor-alkali industry has undergone a major worldwide capacity expansion in recent years. Much of this capacity growth has been due to Chinese efforts to reach self-sufficiency. Chlorine is produced electrochemically from sodium chloride. In this report, we examine two technologies to produce chlorine. The diaphragm cell is the older technology and is no longer competitive on a new construction basis with the latest membrane cells. New construction has used the membrane cell process. This technology is more electrically efficient and has lower capital and operating costs.

A private report by the Process Economics Program Report No. 61E

CHLORINE-ADVANCED COMMERCIAL CHLOR-ALKALI TECHNOLOGY

by Ronald Smith

December 2012

Santa Clara, California 95054

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CONTENTS

1 INTRODUCTION ...... 1-1

2 SUMMARY ...... 2-1 OUR CONCLUSIONS ...... 2-1 Diaphragm Process ...... 2-2 Membrane Process ...... 2-2 Process Economics ...... 2-2

3 INDUSTRY STATUS ...... 3-1 END-USE APPLICATIONS ...... 3-1 PRODUCTION PROCESSES ...... 3-1 DEMAND ...... 3-1 Chlorine ...... 3-1 Caustic Soda ...... 3-3 CAPACITY ...... 3-5 By Region ...... 3-5 By Production Process ...... 3-6 Top 50 Producers ...... 3-7 TRADE ...... 3-8 PRICES ...... 3-9

4 TECHNICAL REVIEW ...... 4-1 SALT ...... 4-2 Sources ...... 4-2 Uses ...... 4-3 Worldwide Production ...... 4-4 Consumption ...... 4-4 Production Process ...... 4-4 Rock Salt ...... 4-4 Cut and Blast Mining of Rock Salt ...... 4-5 Continuous Mining of Rock Salt ...... 4-5 Solution Mining ...... 4-5 Brine Wells ...... 4-8

Brine Well Equipment ...... 4-9 Solar Salt ...... 4-9 Sodium Chloride Crystallization...... 4-9 Salt Field Production ...... 4-9 Solar Salt Harvesting ...... 4-10 Brine Composition and Impact on Processes ...... 4-10 Purity of Various Kinds of Salt ...... 4-10 Typical Specifications for Feed Brine to Electrolyzers ...... 4-11 Zero Liquid Discharge (ZLD) Cogeneration ...... 4-12 Desalination ...... 4-12 Primary Brine Purification for Membrane Cells ...... 4-14 Primary Brine Treatment ...... 4-15 Filtration of Brine ...... 4-15 Secondary Brine Purification for Membrane Cells ...... 4-15 GENERALIZED CHLORINE PLANT ...... 4-17 Main Characteristics of Diaphragm and Membrane Processes ...... 4-18 Monopolar/Bipolar Designs ...... 4-19 Electrolyzer Cell Room Architecture ...... 4-19 Basic Comparison of Various Cell Technologies ...... 4-20 Auxiliary Processes ...... 4-21 Diaphragm Cells ...... 4-21 Diaphragm Cell Process Block Flow Diagram...... 4-22 The Dow Diaphragm Cell ...... 4-24 Typical Diaphragm Cell (Monopolar) ...... 4-25 Diaphragm Cell Liquor Processing ...... 4-26 Caustic Soda from Diaphragm and Membrane Technologies ...... 4-26 Diaphragm Cell Caustic Recovery ...... 4-27 Comparison of Quadruple vs. Triple Effect Concentrators ...... 4-28 Quadruple vs. Triple Effect Energy Savings ...... 4-29 Advantages/Disadvantages ...... 4-29 Anodes for Diaphragm Cells...... 4-29 Advanced Diaphragm Cell Technology ...... 4-29 Structural Specifications of MDC-55 with Energy Saving Anodes ...... 4-30 Voltage Drop Savings of MDC-55 ESA over Standard Expandable Anodes ...... 4-31

Advanced Technology Cathode (ATC) ...... 4-32 Structural Specifications of MDC-55 Using ATC vs. Standard Cathode ...... 4-32 Structural Voltage Drop Savings of ATC vs. Standard Cathodes ...... 4-33 Advanced Diaphragm Cell Technology Advantages ...... 4-33 MEMBRANE CELLS ...... 4-33 Materials of Construction ...... 4-33 Typical Membrane Cell Electrolyzer ...... 4-34 Membrane Cell Block Flow Diagram ...... 4-35 Monopolar Membrane Cell ...... 4-37 Bipolar Membrane Cell ...... 4-38 Bipolar Membrane Cell Process ...... 4-39 Membrane Cell Advantages/Disadvantages ...... 4-40 ADVANCED BIPOLAR MEMBRANE ELECTROLYZER DESIGNS ...... 4-40 Characteristic Features of Current Bipolar Membrane Technologies ...... 4-41 Oxygen Gas Diffusion Cathode ...... 4-41 Asahi Kasei Bipolar Electrolyzers ...... 4-42 Advanced Asahi Kasei Bipolar Electrolyzer ...... 4-43 CEC and Eltech Bipolar Electrolyzers ...... 4-44 Uhde Bipolar Electrolyzers ...... 4-44 Advanced Uhde Element Designs ...... 4-46 Los Alamos Flat Plate Membrane Electrode Assemblies ...... 4-47 Findings and Conclusions ...... 4-53 Differential Pressure Profile of Porous GDE Electrode ...... 4-54 Bayer Gas Pocket Type GDE ...... 4-55 Uhde Falling Film Type GDE Element ...... 4-56 Falling Film Type Air Depleted GDE ...... 4-58 Evolution of Uhde Membrane Electrolyzer Technology ...... 4-59 INEOS Cell Room Revamp Retrofits ...... 4-60 Membrane Cell Voltage Elements ...... 4-61 Total Plant Energy Use Comparison ...... 4-62 Membrane Cell Performance...... 4-63 CELL GAS PROCESSING ...... 4-63

Modern Concept of Wet Chlorine Cell Gas Cooling ...... 4-64 Chlorine Drying ...... 4-64 Conventional Chlorine Cell Gas Drying System ...... 4-65 Advanced Chlorine Cell Gas Drying System ...... 4-65 Improved Concept for Wet Chlorine Cell Gas Drying and Cooling ...... 4-66

Chlorine Cell Gas Drying and Cooling with NCl3 Decomposition ...... 4-67

Improved Concept of CCl4 Use for NCl3 Decomposition ...... 4-68 Typical Operating Ranges for Various Types of Chlorine Compressors ...... 4-69 Reciprocating Chlorine Compressors ...... 4-69 Centrifugal Chlorine Compressors ...... 4-70 Liquid Ring Chlorine Compression ...... 4-70 Use of Water of Brine for Chlorine Liquefaction ...... 4-70 Chlorine Liquefaction with Refrigerant ...... 4-71 Modern Concept of Chlorine Liquefaction without Refrigerant ...... 4-72 Chlorine Product Storage and Transfer (Liquid)...... 4-72 Liquid Chlorine Filling ...... 4-73 Chlorine Vaporization Basic Requirements ...... 4-73 Modern Vaporization Concepts ...... 4-73

5 CHLORINE BY DIAPHRAGM CELL PROCESS ...... 5-1 INTRODUCTION ...... 5-1 PROCESS CHEMISTRY ...... 5-2 PROCESS FEATURES ...... 5-2 Electrodes ...... 5-3 Anodes ...... 5-3 Cathodes ...... 5-3 Diaphragm ...... 5-4 Cell Operation ...... 5-7 Brine Feed ...... 5-7 Caustic Recovery ...... 5-7 Chlorine ...... 5-7 PROCESS DESCRIPTION ...... 5-8 PROCESS DISCUSSION ...... 5-9

MATERIAL BALANCE ...... 5-14 EQUIPMENT LIST ...... 5-20 UTILITY CONSUMPTION ...... 5-23 COST ESTIMATES ...... 5-23

6 CHLORINE BY MEMBRANE CELL PROCESS ...... 6-1 INTRODUCTION ...... 6-1 PROCESS CHEMISTRY ...... 6-9 PROCESS FEATURES ...... 6-9 Electrodes ...... 6-10 Anodes ...... 6-10 Cathodes ...... 6-11 Membranes ...... 6-13 Membrane Materials ...... 6-14 Brine Purity Specifications for Membrane Electrolyzers ...... 6-14 Ion-Exchange Membrane Properties ...... 6-16 Chemical Structure of Perfluorinated Membranes ...... 6-20 Ion-Exchange Capacity ...... 6-22 Selectivity ...... 6-22 Conductivity ...... 6-22 Diffusivity ...... 6-23 Sodium Ion Transport ...... 6-23 Maximum Current Density ...... 6-23 Anion Transport ...... 6-24 Cell Operation ...... 6-24 Effect of Current Density ...... 6-24 Effect of Anolyte Concentrations ...... 6-24 Effect of Operating Temperature ...... 6-24 Caustic Quality ...... 6-24 AC to DC Conversion ...... 6-25 Closed Loop Brine Processing ...... 6-25 Caustic Recovery ...... 6-27 Chlorine Recovery ...... 6-28 Electrolyzer Containment ...... 6-28 Electrolyzer Operation ...... 6-31

Chlorine Cooling ...... 6-31 Chlorine Drying ...... 6-32 Chlorine Compression and Liquefaction ...... 6-32 PROCESS DESCRIPTION ...... 6-33 Brine Purification ...... 6-33 Electrolysis ...... 6-33 Caustic Soda Concentration ...... 6-34 Chlorine Recovery ...... 6-34 Hydrogen Chloride Formation ...... 6-35 Hydrogen Recovery ...... 6-35 PROCESS DISCUSSION ...... 6-35 MATERIAL BALANCE ...... 6-40 EQUIPMENT LIST ...... 6-46 UTILITY CONSUMPTION ...... 6-49 COST ESTIMATES ...... 6-49

APPENDIX A PATENT SUMMARY TABLES ...... A-1

APPENDIX B DESIGN AND COST BASES...... B-1

APPENDIX C CITED REFERENCES ...... C-1

APPENDIX D PATENT REFERENCES BY COMPANY ...... D-1

APPENDIX E PROCESS FLOW DIAGRAMS ...... E-1

3.1 2011 Global Chlorine Demand by End-Use Applications ...... 3-2 3.2 2011 Global Chlorine Demand by Region ...... 3-3 3.3 2011 Global Caustic Soda Demand by End-Use Applications ...... 3-4 3.4 2011 Global Caustic Soda Demand by Region ...... 3-5 3.5 2011 Global Chlorine Capacity Distribution by Region ...... 3-6 3.6 2011 Global Chlorine Capacity Distribution by Technology ...... 3-7 3.7 Historical US Gulf Coast Chlorine, Caustic Soda, Salt, and Electricity Prices ...... 3-9 4.1 Solution Mining ...... 4-6 4.2 Vacuum Pan Salt Plant ...... 4-7 4.3 Single Brine Well Schematic ...... 4-8 4.4 ZLD Cogeneration Plant for Salt Production ...... 4-12 4.5 Competing SWRO Technologies for Production of Pure Water ...... 4-13 4.6 Process Flow Schematic for Primary Brine Purification ...... 4-14 4.7 Secondary Brine Purification Process for Membrane Cells ...... 4-15 4.8 Process Flow Schematic of a RNDS Chelate Plant ...... 4-16 4.9 Generalized Block Flow Diagram of a Chlor-Alkali Plant ...... 4-17 4.10 Monopolar and Bipolar Electolyzer Designs ...... 4-19 4.11 Electrolyzer Cell Room Architechtures ...... 4-20 4.12 Diaphragm Cell Process Block Flow Diagram ...... 4-23 4.13 Dow Diaphragm Cell ...... 4-24 4.14 Conventional Generic Diaphragm Cell ...... 4-25 4.15 Caustic Soda Production from Different Electrolyzer Technologies ...... 4-27 4.16 Diaphragm Cell Caustic Recovery ...... 4-28 4.17 Advanced Diaphragm Cell Technology (Eltech Systems) ...... 4-30 4.18 Advanced Technology Cathode ...... 4-32 4.19 Typical Membrane Cell Electrolyzer (Monopolar) ...... 4-35 4.20 Membrane Cell Process Block Flow Diagram ...... 4-36 4.21 Monopolar Membrane Cell ...... 4-38 4.22 Bipolar Membrane Cell ...... 4-39 4.23 Bipolar Membrane Cell Process ...... 4-40 4.24 Asahi Kasei Bipolar Electrolyzer...... 4-43 4.25 Uhde Electrolyzer Cell Rack ...... 4-45

4.26 Third-Generation Uhde Design...... 4-46 4.27 Conventional Chlor-Alkali Cell vs. Chlor-Alkali Cell with Oxygen Depolarized Cathode ...... 4-48 4.28 Oxygen Depolarized Cathode-Based Flat Plate Design ...... 4-50 4.29 Oxygen Depolarized Cathode Cell Flat Plate Design with Graphite Cathode Hardware ...... 4-51 4.30 Oxygen Depolarized Cathode-Based Flat Plate Design with MEA Type Gas Diffusion Cathode ...... 4-52 4.31 Differential Pressure Profile of a Porous GDE Electrolyzer ...... 4-55 4.32 Bayer Gas Pocket Type GDE ...... 4-56 4.33 Uhde Falling Film Type GDE Element ...... 4-57 4.34 Falling Film Type Air Depolarized GDE ...... 4-58 4.35 Evolution of Uhde Membrane Electrolyzer Technology ...... 4-59 4.36 Uhde Zero-Gap Modular Cell Room Design Concept for Large Scale Plants ...... 4-60 4.37 INEOS Cell Room Revamp/Retrofits (1996–2000) ...... 4-61 4.38 Advanced Concept for Wet Chlorine Cell Gas Cooling ...... 4-64 4.39 Advanced Chlorine Cell Gas Drying System ...... 4-66 4.40 Improved Concept of Wet Chlorine Cell Gas Drying and Cooling ...... 4-67

4.41 Modern Concept of Chlorine Cell Gas Drying and Cooling with NCl3 Decomposition ...... 4-68

4.42 Improved Concept without the Use of Carbon Tetrachloride for NCl3 Decomposition ...... 4-68 4.43 Typical Operating Ranges for Various Types of Chlorine Compressors ...... 4-69 4.44 Liquid Ring Chlorine Compression ...... 4-70 4.45 Use of Chilled Water or Brine for Chlorine Liquefaction ...... 4-71 4.46 Chlorine Liquefaction with Refrigerant ...... 4-71 4.47 Modern Concept for Chlorine Liquefaction without Refrigerant ...... 4-72 5.1 Chlorine by Diaphragm Cell Process Process Flow Diagram ...... E-3 6.1 Brine Treatment Process for Membrane Cells ...... 6-26 6.2 Closed Loop Brine Saturation Process ...... 6-27 6.3 Chlorine by Membrane Cell Process Process Flow Diagram ...... E-9

2.1 Summary of Chlorine Economics ...... 2-3 3.1 Global Top 50 Chlor-Alkali Producers—2011 Average Annual Capacities ...... 3-8 4.1 Purity of Various Kinds of Salt ...... 4-11 4.2 Typical Feed Brine Composition Specifications for Membrane and Diaphragm Electrolyzers ...... 4-11 4.3 Characteristics of Monopolar and Bipolar Electrolyzers ...... 4-18 4.4 Basic Comparison of Conventional Alternative Commercial Cell Technologies ... 4-21 4.5 Main Characteristics of Diaphragm and Membrane Cells ...... 4-22 4.6 Quadruple vs. Triple Effect Separation—Energy Savings Profile ...... 4-28 4.7 Quadruple vs. Triple Effect Separation—Energy Savings ...... 4-29 4.8 Structural Specification Differences of MDC vs. Standard Expandable Anodes .. 4-31 4.9 Voltage Drop Savings of MDC-55 over Standard Expandable Anodes ...... 4-31 4.10 Structural Specifications of MDC-55 Using ATC vs. Standard Cathode ...... 4-32 4.11 Structural Voltage Drop Savings of ATC vs. Standard Cathodes ...... 4-33 4.12 Diaphragm and Membrane Materials of Construction ...... 4-34 4.13 Features Profiles of Current Bipolar Membrane Technologies ...... 4-41 4.14 Total Energy Use Comparison: Conventional Diaphragm vs. Membrane Technology ...... 4-63 5.1 Some Constituents of Seawater and Their Concentrations ...... 5-1 5.2 Chlorine Production by Diaphragm Cell Process Design Basis and Assumptions ...... 5-13 5.3 Diaphragm Plant Stream by Stream Material Balance ...... 5-15 5.4 Diaphragm Plant Tagged Process Equipment List...... 5-20 5.5 Diaphragm Plant Utility Consumption ...... 5-23 5.6 Diaphragm Plant Total Fixed Capital Cost Estimate ...... 5-24 5.7 Diaphragm Plant Total Production Cost ...... 5-26 5.8 Chlor-Alkali Diaphragm Technology Patent Summary ...... A-3 5.9 Caustic Concentration Technology Patent Summary ...... A-25 6.1 Brine Impurities—Sources, Effects, and Mitigation ...... 6-3 6.2 Brine Specifications for Membrane Electrolyzers ...... 6-15 6.3 Structurally Classified Membrane Properties ...... 6-16 6.4 Description of DuPont Membranes ...... 6-17

6.5 Performance Data for Nafion Membranes by Type ...... 6-18 6.6 Description of Asahi Kasei Membranes ...... 6-19 6.7 Performance Data for Asahi Kasei Membranes Infinite Gap Cells ...... 6-20 6.8 Chlorine by Membrane Cell Process Design Bases and Assumptions ...... 6-39 6.9 Membrane Plant Stream-by-Stream Material Balance ...... 6-40 6.10 Membrane Plant Tagged Process Equipment List ...... 6-46 6.11 Membrane Plant Utility Consumption ...... 6-49 6.12 Membrane Plant Total Fixed Capital Cost Estimate...... 6-50 6.13 Membrane Plant Total Production Cost ...... 6-52 6.14 Chlor-Alkali Membrane Electrolytic Technology Patent Summary ...... A-26 6.15 Brine Treatment Technology Patent Summary ...... A-60 6.16 Cell Gas Treatment Technology Patent Summary ...... A-66