983695 - Energy Revaluation of Solid Waste from Cellulose Industry, Finding of Optimal Mixture of Bark, Sawdust, Sludge and Unclassified Pulp to Be Used as Fuel

Cellulose industry in Chile annually produces millions of tons of secondary raw materials (SRM) like sawdust, bark, sludge, and residues ® like unclassified pulp. In an effort to promote circular economy, some SRM are used today in the same Cellulose industrial plant for co-generation of energy and/or steam being combusted on industrial boilers. Nevertheless, this process produces serious problems of emissions of various atmospheric pollutants (gases and particles), mainly due to SRM´s material variability like quantity of water, granulometry, dependence on the season of the year, etc. On the other hand, another part of SRM and residues (SRM+R) generates both environmental and productive problems because they are currently destined and managed in special storage sites, requiring a large area of usable industrial space or even having to be safely disposed of in sanitary authorized landfills. For the given before reasons, the main objective of this research is the energy revaluation of the Cellulose Industry SRM+R in the form of solid fuel, like pellets for use in industrial boilers, transforming into a product attractive for internal or external use in pursuit of the Circular Economy of Cellulose industrial plants. In order to fulfill this goal, the specific objective of this work is to find the optimum mixture of SRM+R (bark, sawdust, sludge, and unclassified pulp) for being used as pellet fuel that produces maximum energy and minimum pollutant emissions. Raw materials and optimized mixture (OM) were submitted to elemental analysis for characterization and combustion tests in order to evaluate pollutant emissions like Black Carbon, Particulate Matter (concentration of PM10, PM2.5 and PM1, and particulate size distribution between 0.27 and 34 µm), and combustion gases (CO, CO2, O2, SO2, HC and NOx). All combustion tests were performed using the controlled combustion chamber 3CE (National patent granted N° 843-2008, 2011 and patent pending CL00058, 2018. International patent granted USA N° US009791151B2, 2017 and PCT granted N°10861353.0-1008-2660587, 2019), an instrument that enables the control of all combustion parameters in order to compare results under reproducible and repetitive combustion operating conditions. Also, raw materials and mixtures were submitted to pelletization tests to obtain an easily manageable fuel that complies with current regulations (ISO 17255-2; type I3).
Preliminary results indicate that mean Emission Factor (EF) for individual raw materials (sawdust, bark, sludge and unclassified pulp) for CO2 is 63% lower than EF CO2 of OM (meaning better combustion), also, mean flame temperature obtained for raw materials is 14% lower than flame temperature obtained in OM combustion tests. Finally mean combustion efficiency calculated for raw materials is 8% lower than OM.
Results obtained are indicative that, from the point of view of combustion efficiency and pollutants emissions, the use as solid fuel of an optimized mixture of SRM+R is better the use of individual raw materials.
Acknowledgments: ANID FONDEF: ID18I10152 and ID18I10182 project from Ministerio de Ciencia, Tecnología, Conocimiento e Innovación of Chile for financial assistance. Support from the CELCO-ARAUCO company is also acknowledged.