Impact of different kinds of biomass mixtures on combustion performance, interaction and synergistic effects in cofiring of coal and biomass in steam power plants

The cofiring of biomass and coal may be one of the most effective methods to improve energy utilization efficiency and reduce greenhouse gas emissions.This study aims to investigate combustion performance,interaction and synergistic effects in the cofiring of coal and three types of biomass.Blended fuel consisting of coal and three types of biomass such as sawdust,rice husk and solid recovery fuel was selected as the research object.Ultimate and proximate analysis and differential thermogravimetric analysis with heating rates of between 10°C and 40°C/minute are used to analyse combustion characteristics.Simulation of combustion in a 600-MWe steam power plant with a Carolina-type boiler is also carried out with the help of computational fluid dynamic(CFD)analysis to see the effect of the interaction and synergy of the mixed fuel on the performance of the steam generator.The effect on the com-bustion process in the combustion chamber of a steam power plant is also simulated.Based on the analysis of several test results of parameters such as ignition temperature,burnout temperature,calorific value of the fuel mixtures as well as CFD simulation,the results of the study show a strong indication of a positive synergy in mixing some of these biomasses as compared with a fuel mix-ture consisting only of coal and one type of biomass.Practically no power derating of the boiler occurs until the biomass content in the fuel mixture is~30%on a mass basis.The reduction in greenhouse gas emissions also appears significant from the results of the CFD simulation of this study,which is characterized by a decrease in the fraction of CO_(2) in flue gas from 21.5%for coal alone as fuel to 15.9%in the case of cofiring excluding the CO_(2) attributed to the biomass.

Experimental analysis on calcination and carbonation process in calcium looping for CO_(2) capture: study case of cement plants in Indonesia

Carbon dioxide(CO_(2))is the main contributor to greenhouse gases that affect global warming.The industrial sector is the third largest producer of CO_(2) and the cement industry is one of the industries that consistently produces the most significant CO_(2) emissions.The cement industry produces 5-8% of global CO_(2) emissions.Several methods for reducing specific CO_(2) emissions have been reported in the cement industry,including calcium looping,which uses the reversible reaction between calcination[calcium carbonate(CaCO_(3))decomposition]and carbonation[CO_(2) capture by calcium oxide(CaO)].This work investigates calcium looping employing limestone obtained directly from several cement factories in Indonesia to observe the carbon-absorption characteristics of limestone from different mining locations.The experiment was carried out using a tube furnace equipped with a controlled atmospheric condition that functions as a calciner and a carbonator.X-ray diffraction and scanning electron microscopy with energy-dispersive x-ray spec-troscopy characterization were conducted to analyse the changes in the experimental samples.The results demonstrated that the reactor configuration was capable of performing the calcination process,which converted CaCO_(3) to calcium hydroxide[Ca(OH)_(2)],as well as the carbonation process,which captured carbon and converted it back to CaCO_(3).Parametric analysis was performed on both reactions,including pressure,temperature,duration,particle size and reaction atmosphere.The results show that the limestone obtained from all sites can be used as the sorbents for the calcium-looping process with an average reactivity of 59.01%.Limestone from cement plants in various parts of Indonesia has the potential to be used as carbon sorbents in calcium-looping technology.With a similar CO_(2) concentration as the flue gas of 16.67%,the experimental results show that Bayah limestone has the maximum reactivity,as shown by the highest carbon-content addition of 12.15 wt% and has the highest CO_(2)-capture capability up to>75% per mole of Ca(OH)_(2) as a sorbent.Similar levels of the ability to capture CO_(2) per mole of Ca(OH)_(2) can be found in other limestones,ranging from 14.85% to 34.07%.The results show a promising performance of raw limestones from different mining sites,allowing further study and observation of the possibility of CO_(2) emission reduction in the sustainable cement-production process.