Abstract
Purpose: This study evaluates the potential of biomass ash as raw clinker material and the influence of biomass feedstock and thermal conversion technology on biomass ash properties. Methods: A set of criteria for biomass feedstock and ash properties (i.e. CaO/SiO2 ratio and burnability) are established. A large dataset was collected and the best combination of biomass feedstock and conversion technology regarding the desired ash quality was identified. Results: Wood biomass has the highest potential to provide the right CaO/SiO2 ratio which is needed to form clinker minerals. Bark content and exogenous Si inclusion in wood biomass have a large influence on the CaO/SiO2 ratio. Paper sludge is composed of Ca, Si and Al and can potentially serve as a source of cement elements. Wood fly ash from pulverized fuel combustion can substitute a considerable amount of raw clinker materials due to its similar burnability. The replacement ratio is determined by the content of adverse elements in the ash (i.e. MgO2 and P2O5). Conclusion: Using biomass ash to lower the CO2 emission from clinker production depends on the joint effort of bioenergy producers, by providing higher quality biomass ash, and cement makers, by adapting the kiln operation to enable a high level of raw material replacement by biomass ash.The presented evaluation of the ash production chain, from biomass selection through combustion technology and ash management, provides new insights and recommendations for both stakeholders to facilitate this sustainable development.Graphic
Highlights
Saving energy and conserving natural resources, as well as reducing CO2 emissions and managing wastes are becoming more and more important measures to enable a transition towards a circular economy
Due to the development of new concepts such as the circular economy and the environmental and economic benefits that may be obtained from its beneficial reuse, biomass ash is starting to be seen as an integrated part of the biomass energy production chain and some studies have explored opportunities to replace a portion of cement raw materials with waste and by-products from other processes
Samples belonging to the wood and woody biomass (WWB) group generally are located in the bottomleft area of the triangular diagram meaning that the concentration of clinker forming elements is higher than the adverse ones
Summary
Saving energy and conserving natural resources, as well as reducing CO2 emissions and managing wastes are becoming more and more important measures to enable a transition towards a circular economy. The cement industry has increased its efforts to lower C O2 emissions, including: (i) improving the energy efficiency of the kilns; (ii) replacing fossil based fuels with alternative energy sources (such as animal residues, sewage sludge and waste oil); (iii) substituting the traditional Portland cement with secondary cementitious materials, such as blast furnace slags and coal combustion fly ash [3]. Several researchers have investigated the use of agricultural waste ashes as constituents in concrete, including rice ash [23, 24], bagasse ash [4] and palm oil ash [25, 26] Those agro-waste ashes, containing a large amount of silica in amorphous form, have been shown to hold potential for use as pozzolanic material replacing cement. The existing literature generally addresses site specific case studies, often dealing with a single ash stream from a specific power plant and geographical region [27, 29], rather than general application principles
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