Kraft black liquor concentration with graphene oxide membranes: Process simulations and technoeconomic analysis

Abstract

Black liquor (BL) dewatering by multi-effect evaporation in the kraft papermaking process is highly energy-intensive. It was previously shown that graphene oxide (GO) nanofiltration membranes can remove lignin, other organics, and inorganic salts from BL while exhibiting stability in caustic BL conditions. Here, we design and simulate several candidate dewatering processes and evaluate their technoeconomic characteristics. All processes concentrate BL from 15 to 30 wt% solutes while producing aqueous permeate.Two process options were analyzed-option A including "last-mile" permeate treatment to reduce solutes to 0.2 wt%, and option B excluding this treatment and producing a 3-4 wt% solutes stream. These processes were simulated in custom-built ASPEN Plus flowsheets interfaced with Microsoft Excel and MATLAB. All processes deliver large (>40%) energy savings. Detailed technoeconomic analysis showed that option A processes are profitable in mills equipped with condensing turbines, but unprofitable with only purchased fuel savings. Option B processes are profitable in both situations, but require the caustic permeate to be utilized in other kraft process units. They are also profitable with electricity generation when operated at smaller scales matching the requirements of other process units. Monte-Carlo sensitivity analysis shows that Option A can yield median 20-year NPVs up to ~$10MM and Option B up to ~$25MM. Overall, GO membrane-based BL dewatering is economically promising, assuming successful slipstream piloting and scale-up campaigns. It would have immediate sustainability benefits from large energy savings, and broader implications for biorefinery processes due to the ability to fractionate biomass feedstock components under harsh conditions.

Catalytic Upgrading of a Mixed Hydroxy Acid Feedstock Derived from Kraft Black Liquor

“…Black liquor (BL) is generated in large amounts (estimated >1 billion metric tons/year globally) in the pulp and paper industry utilizing the kraft process. , In addition to lignin, inorganic sulfur salts, alkali, and carbonates, BL contains a range of C 1 –C 6 acids . A typical kraft mill generating 4 MMT/yr of BL can produce about 0.1–0.2 MMT/yr of hydroxy acids (HAs).…”

Transport properties of graphene oxide nanofiltration membranes: Electrokinetic modeling and experimental validation

“…19 and enabling process simulations, 28,29 intensification/ optimization, 30,31 and technoeconomic analysis (TEA). 32,33 Graphene oxide (GO) membranes are rapidly emerging as a nextgeneration nanofiltration membrane separation platform 8,9,[34][35][36][37][38][39][40][41] with high water permeability, 8,39,42 selectivity, 8,37 and fouling resistance, 43 due to their unique physical and chemical properties. 44 Recent work has also pioneered the development of GO membranes for demanding applications such as processing of kraft black liquor, wherein GO membranes provide robust stability and NF characteristics for rejection of lignin, other organics, and inorganics.…”

“…44 Recent work has also pioneered the development of GO membranes for demanding applications such as processing of kraft black liquor, wherein GO membranes provide robust stability and NF characteristics for rejection of lignin, other organics, and inorganics. 32,40,45,46 Given the present stage of GO membrane science and technology, 47,48 there is a significant need to develop appropriate models for describing separation in GO membranes, which have distinctive transport mechanisms.…”

“…Parametrization and validation of these models with experimental data allows them to be used for predictive purposes, 21 thereby significantly reducing the need for experimentation 19 . and enabling process simulations, 28,29 intensification/optimization, 30,31 and technoeconomic analysis (TEA) 32,33 …”

“…Graphene oxide (GO) membranes are rapidly emerging as a next‐generation nanofiltration membrane separation platform 8,9,34–41 with high water permeability, 8,39,42 selectivity, 8,37 and fouling resistance, 43 due to their unique physical and chemical properties 44 . Recent work has also pioneered the development of GO membranes for demanding applications such as processing of kraft black liquor, wherein GO membranes provide robust stability and NF characteristics for rejection of lignin, other organics, and inorganics 32,40,45,46 . Given the present stage of GO membrane science and technology, 47,48 there is a significant need to develop appropriate models for describing separation in GO membranes, which have distinctive transport mechanisms.…”