Intricacies of caustic production from industrial green liquor using bipolar membrane electrodialysis. Issue 3 (June 2022)

• Record Type: Journal Article
• Authors: Eswaraswamy, Bhuvanesh; Mandal, Priyabrata; Goel, Priya; Chandra, Anusha; Chattopadhyay, Sujay
• Is Part Of: Journal of environmental chemical engineering. Volume 10:Issue 3(2022)
• Publication Date: 2022-06
• Subjects: Caustic -- Pulp and paper -- Green liquor -- Bipolar membrane -- Electrodialysis -- Ion transport; Chemical engineering -- Environmental aspects -- Periodicals; Environmental engineering -- Periodicals; Chemical engineering -- Environmental aspects; Environmental engineering; Periodicals; 660.0286
• DOI: 10.1016/j.jece.2022.107628
• Languages: English
• ISSNs: 2213-2929

Abstract

Abstract: Lime based causticization of green liquor (GL, rich in Na2 CO3 ) to white liquor (rich in NaOH) followed by lime recycling in pulp and paper mills is an energy intensive and environmentally hazardous technique. Recently membrane electrolysis is proposed to be an alternative to this, where use of single cation exchange membrane (CEM) between two electrodes limits the processing volume of the feed stream. This can be overcome through BMED (bipolar membrane electrodialysis) technique, where multiple cell pairs can be applied to process larger feed volume. Current report investigates optimization of NaOH production from synthetic-GL using a BMED stack with variation of current density (25, 50, 75 and 100 mA·cm −2 ), GL concentration (100%, 75%, and 50% v/v), and feed temperature (27, 40 and 50 ℃) along with multiple cell pair arrangement (1, 2 and 3). With 50 mA·cm −2, ~1.6 mol·L −1 of NaOH could be produced from 500 mL of synthetic-GL in 5 h using a three-cell pair BMED setup (effective area of 32 cm 2 per cell pair), where current efficiency and energy consumption estimates were ~88.0% and ~4.7 kWh·kg −1, respectively. Under identical conditions, NaOH production performance from industrial-GL was quite comparable (deviation < 5%) to that of synthetic-GL. Graphical Abstract: ga1 Highlights: Bipolar membrane electrodialysis for caustic production from green liquor. Investigated the influence of number of cell pairs on NaOH production. Compared and validated performance with synthetic and industrial sample. 1.6 mol·L −1 caustic produced at 4.7 kWh·kg −1 with 88% current efficiency. Proposed as alternative technology for energy intensive conventional process.