R Buitrago-Tello et al.
Original Article: Linerboard production and decarbonization
Graphene oxide nanofiltration membranes The GO nanofiltration membrane system concentrated weak black liquor from 15% to 30% dissolved solids, significantly reducing the energy load on the evaporators and producing process-quality water that could be reused for pulp washing. 21 However, this system operated at high pressure (60 MPa), 21 which increased electricity demand. The reduction in steam flow to the turbines decreased on-site electricity generation, leading to higher Scope 2 emissions. The membranes also partially rejected dissolved inorganics, impacting chemical requirements. A mass and energy balance simulation was conducted to address these combined effects on electricity and chemical use. Two scenarios were considered: a system with four membranes (membrane case 1) and a system with five membranes (membrane case 2). Detailed information is The mechanical vapor recompression system (MVR) reduced the steam demand by using the recompressed water vapor from the black liquor evaporation as a heat source. In this scenario, an additional external evaporation body was installed; the steam from this body was recompressed in a low-speed centrifugal fan and the mechanically heated vapor was used as a heating medium in the same evaporator body. 7 The system used electricity rather than thermal energy (steam) to preconcentrate the weak black liquor from 15% to 25%. 7 Like the membrane system, for the MVR the on-site electricity capacity dropped by the reduction in the turbine’s steam flow, affecting the emissions from Scope 2. The supporting information section describes the assumptions for this scenario. included in the supporting information section. Mechanical vapor recompression
this reduced the water to be evaporated in the drying section but with a 3% to 5% increase in the electricity demand in comparison with a conventional press. On the other hand, incorporating a nylon mesh into the felt reduced rewet significantly by rupturing the liquid channels between felt and web. The nylon mesh was embedded into the surface of the continuous press felt and travelled as an integral part of the moving press felt. This technique has been shown on a laboratory scale to increase the press solids from 48% to 61% on 120 g/m 2 southern bleached softwood kraft pulp handsheets. 24 Drying section The drying section was one of the most energy-demanding areas; 50% to 60% of the heat energy was consumed in the dryers. 31 Condebelt drying is a technology that saves an estimated 1.6 GJ/t paper in steam (around 15% of the steam demand) and 20 kWh/t paper in electricity, 25 and it is suitable for the production of linerboard. 31 In a condebelt dryer, the paper web is passed between a pair of flexible steel belts. The system is heated from one side using steam and cooled on the other with water. The condensate is collected in the bottom-cooled side by a pair of fabrics. Besides the energy savings, some properties are improved, such as strength (by 20% to 60%), surface smoothness, dimensional stability, and resistance against humidity. 25 Marginal abatement cost curves The alternatives were analyzed by developing a marginal abatement cost curve (MACC). This curve was built based on the cost of avoided carbon (CAC) in US $/ton of CO 2 -eq. avoided, and the CO 2 -eq. reduction achieved by implementing each technology for 10 years. The MACC was built considering Scope 1 and 2 emissions, and the total emissions associated with the entire system (Scope 1, 2, and 3 emissions). Scope 3 emissions included all of the upstream emissions associated with inputs to the process. The cost of each technology was determined as the net present value (NPV) in an 11-year lifetime, of which the first year was for construction, with a 15% rate of return. The capital expenditure (CAPEX) and changes in the operating cost are detailed in the supporting information section. The NPV and the CAC of each alternative were also estimated considering two carbon-offset prices, $11/metric ton avoided by 2030 and $47/metric ton avoided by 2050. These values are prices projected for technologies that avoid carbon emissions: 32
Paper machine technologies Press section
The wet-press section played a critical role because an essential fraction of the steam demand came from the evaporation of water from the paper. The wet-press section was, therefore, the last chance to remove the water before evaporative drying. 22 It is estimated that 3% to 8% of dryer steam consumption can be saved by improving the solids content of the web formed after the press section. 23 Two alternatives were included for this section: the adaptation of a shoe press, and the introduction of a nylon mesh into the press felt. A shoe press pressed the paper web between a pair of rollers, with one roller coated in a flexible ‘shoe’. The shoe press improved mechanical dewatering by extending the dwell time in the nip, increasing 4% to 7% points of dryness; 22
NPV ( $ ) Total carbon avoided ( tons ofCO 2 )
CAC =
(1)
6
© 2025 The Author(s). Biofuels, Bioproducts and Biorefining published by Society of Industrial Chemistry and John Wiley & Sons Ltd. | Biofuels, Bioprod. Bioref . (2025); DOI: 10.1002/bbb.2790
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