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This work is focused on the possibilities of utilization of ashes from fluidized bed combustion, i.e. FBC ashes, for the manufacturing of hydraulic lime. Alternative hydraulic binders are becoming very popular in the present due to requirements on reducing CO2 emissions. FBC ash is an easily available, though not easily usable raw material. Because...
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... In the present day, the need to obtain alternative binding materials is caused by solution of the following problem: reduction of СО 2 emissions, production of binding materials for restoration and production of hydraulic binding agent, which is not worse than Portland cement. СО 2 emissions, as a rule, can be reduced by dilution of the main binding material, for example, lime, natural products or by-products of different production industries [2]. Various puzzolanes (primarily ashes) are used as the additives depending on what problem of СО 2 emissions and waste disposal is resolved. ...
The purpose of this research is to equip the roman cement with properties exceeding the properties of the known analogies.
Roman cement’s compositions modified by chemical and mineral additives have been developed and proposed. The mode of calcinations of carbonate and clay raw material with high MgO has been optimized. As a result, the durability of roman cement from 15 to 22 MPa has been received. Mineral additives like slag, zeolite breed and clay dust were chosen and used that rose the durability from 22 to 28 MPa. Plasticizers and hardening accelerators were chosen and used that allowed rising the durability up to 35 MPa relatively. A combination of complex additives have been proposed.
To optimize the mode of calcinations and to define a combination of complex additives the method of mathematical planning was used. The dependence of binder’s strength from the temperature, durability of calcinations, saturation rate, type and consistence of modified additives has been acquired.
Modified roman cement has the advantages if compared with known analogies and has the following features: strength 35MPa, normal consistency 30%, setting time is not earlier than 35 minutes, the end is not late than 420 minutes, softening rate is 0.98.
Modified roman cement can be successfully used to produce dry building mixtures (mortar’s strength 5,10, 15 MPA), low strength mortars (strength 5,7.5 MPa) and concret (strength 10, 15, 20, 25 MPa) and other building materials.
Structure of carbonate raw material and clay for the production of roman cement is recommended.
... Extensive research has been conducted for woody biomass ash valorisation by application in acid soils substituting liming products (Arshad et al., 2012;Cruz et al., 2017;Dvořák et al., 2017;Park et al., 2012), demonstrating that this practice is a good opportunity to valorise this residue, since woody biomass ash brings a more rapid soil pH change than using traditional liming products (Pitman, 2006). This effect can be attributed to its fine structure and chemical composition (Arshad et al., 2012;Lickacz, 2002). ...
... The recirculation of woody biomass ash in forest soils reduces the need for landfills, leads to the return of valuable nutrients to forest ecosystems and counteracts soil acidification, making energy production from forest biomass combustion more sustainable (Bang-Andreasen et al., 2017;Brännvall et al., 2014;Freire et al., 2015). Extensive research has been conducted regarding the application of woody biomass ash in acid soils substituting liming products (Arshad et al., 2012;Cruz et al., 2017;Dvořák et al., 2017;Park et al., 2012). ...
The production of bioenergy from forest biomass residues has been increasing in the last years in Portugal, mainly as a consequence of concerns related to climate change and forest fires. However, the potential environmental impacts associated with its production should be quantified to support decision-making. This quantification can be performed by using life cycle assessment (LCA), a methodology that evaluates the entire life cycle of a product or process (from the extraction of the raw materials until its end-of-life), allowing to identify the most significant stages and processes along the life cycle. Currently, there is a limited number of LCA studies concerning the production of bioenergy from forest biomass residues. In addition, those studies usually exclude the end-of-life stage (ash management) or only consider ash disposal in landfill, disregarding the valorisation alternatives. Furthermore, given the constraints on forest residues availability, it is important to assess the best use for these residues from an environmental perspective. Therefore, this thesis aims to contribute to increase the knowledge of the environmental performance of the bioenergy sector in Portugal. The two most representative combustion technologies for electricity production from forest biomass residues (grate
furnace and fluidised bed) are assessed and compared using LCA throughout all stages of the value chain, namely, forest management, collection, processing, transportation, energy conversion and end-of-life. Moreover, LCA is applied to the end-of-life stage of the ash generated during the combustion of forest biomass residues to evaluate two
valorisation alternatives (construction materials and soil amelioration) and compare with ash landfilling. Various scenarios are included in order to identify the most efficient option from an environmental point of view. Additionally, a consequential LCA is used to evaluate the best valorisation option for the forest biomass residues, namely, electricity, heat or
bioethanol, in comparison with a baseline that entails leaving the residues in the forest soil and energy is produced from fossil fuels. The results show that fluidised bed presents smaller environmental impacts than grate furnace for all impact categories analysed. Regarding ash valorisation in construction materials, all scenarios assessed had a lower environmental impact than landfilling in all the impact categories. However, the valorisation of ash for soil amelioration presents higher environmental impacts than landfilling for some impact categories, indicating that it can potentially increase the amount of pollutants in the soil. Finally, the results of the consequential LCA indicate that the best use of the forest biomass residues is cogeneration of electricity and heat, but for some impact categories it would only perform environmentally better than the baseline
under particular conditions.
... The recirculation of woody biomass ash in forest soils reduces the need for landfills, leads to the return of valuable nutrients to forest ecosystems and counteracts soil acidification, making energy production from wood combustion more sustainable (Bang-Andreasen et al., 2017;Brännvall et al., 2014;Freire et al., 2015). Extensive research has been conducted regarding the application of woody biomass ash in acid soils substituting liming products (Arshad et al., 2012;Cruz et al., 2017;Dvořák et al., 2017;Park et al., 2012). In general, crops respond better to neutral soils than to acid soils and, therefore, the addition of woody biomass ash is a good option for liming, since woody biomass ash is alkaline, contains high values of oxides and hydroxides of calcium and readily reacts with acidic components in the soil (Demeyer et al., 2001;James et al., 2012;Lin et al., 2007). ...
The increasing use of forest biomass as a fuel for power plants due to environmental concerns will certainly increase the amount of woody biomass ash produced. Because of the environmental problems derived from woody biomass ash disposal, an important aspect for the sustainable development of the energy sector is the implementation of effective ash management strategies. The purpose of this study is to assess the environmental impacts of woody biomass ash landfarming for soil amelioration through a Life Cycle Assessment. The baseline scenario corresponds to the current most common practice of woody biomass ash management (landfilling), and two different landfarming alternatives were assessed: liming and fertilisation. Credits were given to the system due to the substitution of three traditional lim-ing products and five traditional fertilisers. Woody biomass ash landfarming presented satisfactory performance in five impact categories under study in comparison to landfilling. When woody biomass ash was used for liming, the environmental savings were more pronounced when substituting hydrated lime. For potassium supply, the substitution of potassium nitrate by woody biomass ash presented the best environmental performance, while for phosphorus supply, the environmental savings were more pronounced substituting single superphosphate. However, in four impact categories, the environmental impacts of ash landfarming exceeded the impacts of ash landfilling, due to the emission to soil of nutrients and trace elements to soil. But this does not necessarily imply increased risks for the environment, as the potential pollutants leaching depends on their bioavailability in the soil.
... The LSF "Lime Saturation Factor" represents the ratio of the CaO present in Clinker to its ability to bind with the most basic compounds [6,7]. When the saturation factor in lime is greater than 100 %, there is imbalance between the constituents. ...
... Considering ideal conditions, ie no overdosage of the raw, good fineness of grinding, good homogenization of the flour, good combustion (complete) and proper coating of the kiln (good insulation). If the above conditions are verified, we could be concluded that the presence of free lime in the clinker is due solely to the retrogradation of C3S, according to the chemical reaction (7). We can be understood that the weight of the liter of clinker is due essentially to the weight of the C3S. ...
The cement industry is one of the most standardized industries from the raw materials preparation to the cement manufacture, through the raw materials grinding and the crude flour firing. The raw materials used are mainly limestone (if Dolomite CaCO3.MgCO3) and Clay (If Kaolinite: Al2O3.2SiO2.(OH)4 ; if Montmorillonite : (Na,Ca)0,3 (Al,Mg)2Si4O10(OH)2.nH2O). At each stage or level of the process, there are existing standards and principles to be respected. These Cement standards require especially that the free lime active (CaOfree) value be significantly less than 2 % by weight. The CaO free causes damage to the mortar, combining with water (H2O) to produce slaked lime (Ca(OH)2), when it is in high content in clinker. Thus, the present article is concerned with the study of specific parameters which help to judge the quality of the clinker produced; those are clinker liter weight and free lime content (CaOfree) in the clinker which are strongly linked to the dosing and grinding of raw materials. It present also in a precise way the various aspects related to the raw materials preparation, the various causes leading to the presence of CaOfree in the clinker, and finally establish a correlation between the density of the clinker (weight of the liter) and free lime, which is important for the adjustment of raw materials (upstream) and cement produced (downstream). The results show that clinker density decreases exponentially with the increasing of free lime content. The weight of the liter for an economic step of the furnace is thus between 1100 and 1250 g/l, where the content of free lime is clearly less than 2 % of the weight.
... El valor obtenido del módulo hidráulico se encuentra dentro de los límites recomendados debido a que para valores superiores a este intervalo el aglomerante no presentara estabilidad con relación a su volumen, disminuye la resistencia química y aumenta el calor de hidratación; para valores inferiores al intervalo señalado, el aglomerante presentaría resistencia muy baja, razones por la que se presentaría agrietamiento por expansión [19,20]. ...
