Towards closed water loops in modern bioproduct mills: evaporation of organic-acid-rich D 0 filtrate from ECF bleaching
Source abstract
Abstract
Abstract In modern bioproduct mills, process improvements have reduced acidic bleaching filtrate volumes to 5 m 3 /ADt, making its treatment increasingly feasible. This study investigates closing the bleaching water loop by evaporating the D 0 filtrate from an ECF D 0 -E op -D 1 bleaching sequence operated without added acids for pH-control. Under these conditions, the D 0 filtrate contains enhanced levels of organic acids. Pretreatment by filtration removed fiber-derived solids and Ca/Si-rich non-process elements, while neutralization improved process safety and cleanliness, and condensate quality. Evaporation produced 4.8 m 3 /ADt of clear condensate suitable for internal reuse, with no detectable chloride, chlorate, or sulfate and methanol as the principal volatile; neutralization suppressed formic and acetic acids to non-volatile salts. The concentrate, after incineration, yielded ash dominated by 61–67 % NaCl, accompanied by carbonate-containing compounds reflecting the high organic-acid feed. Recovery of 13 kg/ADt NaCl for chlorate-plant feed is plausible but will require brine purification to meet vacuum-salt specifications. Overall, D 0 filtrate evaporation enables condensate reuse, recovery of ∼1.5 kg/ADt methanol, and concentrate valorization, advancing water-loop closure in modern bioproduct mills.
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Research context
OpenAlex topics: Coagulation and Flocculation Studies · Phosphorus and nutrient management · Anaerobic Digestion and Biogas Production
SciVX discovery tags are terminology-based. OpenAlex topics are source-provided classifications.
Affiliations
Department of Bioproducts and Biosystems , School of Chemical Engineering, Aalto University , Vuorimiehentie 1 , Espoo , 02150 , Finland
Metsäliitto Osuuskunta , Espoo , 02100 , Finland
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