Connecting wastes to resources for clean technologies in the chlor-alkali industry: a life cycle approach

Our current economic model is experiencing increasing demand and increasing pressure on resource utilisation, as valuable materials are lost as waste. Moving towards a circular economy and supporting efficient resource utilisation is essential for protecting the environment. The chlor-alkali industry is one of the largest consumers of salt, and efforts have been made to reduce its electricity use. Furthermore, KCl mining wastes have received increasing attention because they can be transformed into value-added resources. This work studies the influence of using different salt sources on the environmental sustainability of the chlor-alkali industry to identify further improvement opportunities. Rock salt, solar salt, KCl waste salt, vacuum salt and solution-mined salt were studied. Membrane cells in both bipolar and monopolar configurations were studied and compared to the emergent oxygen-depolarised cathode (ODC) technology. Life cycle assessment was applied to estimate the cradle-to-gate environmental impacts. The natural resource (NR) requirements and the environmental burdens (EBs) to the air and water environments were assessed. The total NR and EB requirements were reduced by 20% when vacuum salt was replaced with KCl. Moreover, the environmental impacts estimated for the monopolar membrane using KCl were comparable to those generated for the bipolar membrane using VS. The difference between the monopolar and bipolar scenarios (17%) was slightly higher than that between the bipolar and ODC technologies (12%). This work demonstrates the importance of studying every life cycle stage in a chemical process and the environmental benefit of applying a circular economy, even in energy intensive industries such as the chlor-alkali industry.

[1]  Brinkmann Thomas,et al.  Best Available Techniques (BAT) Reference Document for the Production of Chlor-alkali. Industrial Emissions Directive 2010/75/EU (Integrated Pollution Prevention and Control) , 2014 .

[2]  Rubén Aldaco,et al.  Environmental Sustainability Normalization of Industrial Processes , 2009 .

[3]  R. Venterea.  Climate Change 2007: Mitigation of Climate Change , 2009 .

[4]  André Bardow,et al.  Comparative LCA of multi-product processes with non-common products: a systematic approach applied to chlorine electrolysis technologies , 2013, The International Journal of Life Cycle Assessment.

[5]  Niklas von der Assen,et al.  Industry-Cost-Curve Approach for Modeling the Environmental Impact of Introducing New Technologies in Life Cycle Assessment. , 2015, Environmental science & technology.

[6]  Yohannes Kiros,et al.  Low Energy Consumption in Chlor-alkali Cells Using Oxygen Reduction Electrodes , 2008 .

[7]  Adisa Azapagic,et al.  Assessing Management Options for Wastewater Treatment Works in the Context of Life Cycle Assessment. , 1998 .

[8]  Steven De Meester,et al.  The recyclability benefit rate of closed-loop and open-loop systems: a case study on plastic recycling in Flanders , 2015 .

[9]  H. Hiller.  In: Ullmann''''s Encyclopedia of Industrial Chemistry , 1989 .

[10]  Robert Ayers,et al.  The Life‐Cycle of Chlorine, Part I: Chlorine Production and the Chlorine‐Mercury Connection , 1997 .

[11]  Daniel Weisser,et al.  A guide to life-cycle greenhouse gas (GHG) emissions from electric supply technologies , 2007 .

[12]  Zachary A. Coventry,et al.  Comparative life cycle assessment of solid waste management strategies , 2016, Clean Technologies and Environmental Policy.

[13]  Hans-Jürgen Dr. Klüppel,et al.  The Revision of ISO Standards 14040-3 - ISO 14040: Environmental management – Life cycle assessment – Principles and framework - ISO 14044: Environmental management – Life cycle assessment – Requirements and guidelines , 2005 .

[14]  Mahmoud Bady,et al.  Environmental impact assessment of the Egyptian cement industry based on a life-cycle assessment approach: a comparative study between Egyptian and Swiss plants , 2016, Clean Technologies and Environmental Policy.

[15]  Pere Fullana,et al.  Environmental sustainability assessment in the process industry: A case study of waste-to-energy plants in Spain , 2014 .

[16]  Xu Xu,et al.  Life cycle assessment of caustic soda production: a case study in China , 2014 .

[17]  Pedro M. Castro,et al.  Life cycle assessment and optimization of an iron making system with a combined cycle power plant: a case study from China , 2016, Clean Technologies and Environmental Policy.

[18]  Tieyong Zuo,et al.  Life cycle inventory for electricity generation in China , 2007 .

[19]  Norbert Wagner,et al.  Development of high-performance silver-based gas-diffusion electrodes for chlor-alkali electrolysis with oxygen depolarized cathodes , 2012 .

[20]  Adisa Azapagic,et al.  Environmental Assessment of Dimethyl Carbonate Production: Comparison of a Novel Electrosynthesis Route Utilizing CO2 with a Commercial Oxidative Carbonylation Process , 2016 .

[21]  André Bardow,et al.  Cleaner chlorine production using oxygen depolarized cathodes? A life cycle assessment , 2014 .

[22]  Waleed R. Abdullah,et al.  PREPARATION OF HIGH PURITY MAGNESIUM OXIDE FROM SEA BITTERN RESIDUAL FROM NaCl PRODUCTION IN Al-BASRAH SALTERN, SOUTH IRAQ , 2013 .

[23]  T. Murugesan,et al.  The chlor-alkali process: Work in Progress , 2014, Clean Technologies and Environmental Policy.

[24]  María Margallo,et al.  Environmental challenges of the chlor-alkali production: Seeking answers from a life cycle approach. , 2017, The Science of the total environment.

[25]  Jane C. Bare,et al.  Life cycle impact assessment research developments and needs , 2010 .

[26]  María Margallo,et al.  Environmental Sustainability Assessment of an Innovative Cr (III) Passivation Process , 2013 .

[27]  Adisa Azapagic,et al.  Life cycle assessment as a tool for improving process performance: A case study on boron products , 1999 .