Co-firing System Research Articles

Experimental Study on NOx Generation and Slip NH3 Treatment in a Small Scale Coal-ammonia Co-firing System

Experimental Study on NOx Generation and Slip NH3 Treatment in a Small Scale Coal-ammonia Co-firing System

Life cycle assessment of ammonia co-firing power plants: A comprehensive review and analysis from a whole industrial chain perspective

Ammonia, a reliable low-carbon alternative fuel with energy storage capabilities, has garnered increasing attention for its application of co-firing in coal-fired power plants as a strategy to mitigate direct carbon emissions. However, various types of ammonia production technologies result in diverse economic feasibility and emission intensities. Simultaneously, each stage, spanning from upstream processes such as raw material extraction to downstream applications, contributes to carbon emissions, which cannot be ignored. It is crucial to select the appropriate assessment method to determine the transformation pathways for co-firing systems. To this end, this review presents a comprehensive life cycle assessment of ammonia co-firing systems from a whole industrial chain perspective, encompassing the entire gamut of processes from fuel production and transportation to co-firing. Studies of the industrial chain perspective and of life cycle assessment methodology that are uniquely tailored for co-firing systems are presented. A nuanced exploration of distinct technologies across the spectrum of system processes ensues, including the advantages, limitations, and trends in advancement, based on carbon emissions and economic criteria. Considering the diverse fuel production, especially ammonia, typologies and intricate processes have undergone comprehensive review. The combustion characteristics, emissions, and economic factors associated with the co-firing process are systematically summarized, drawing upon aspects such as dynamics, experiments, simulations, and demonstration projects. This study illuminates the progression and technology selection of co-firing systems across multiple stages of the whole industry chain, thereby furnishing insights relevant to the low-carbon transformation of ammonia co-firing with coal in power plants.

Low-carbon fuel reburning for CO2 and NOx reduction in pulverized coal firing system

Using low- or zero-carbon fuels is necessary to reduce CO2 emissions. Gas reburning technology can be applied to existing coal boilers to reduce not only CO2 but also NOx emissions. In this study, we confirmed the gas reburning effect using lab-scale equipment based on the consumption coal used in real-scale boilers, with the aim of practical application. Bituminous coal was used as the reference fuel, and sub-bituminous coal was blended to determine whether coal blending has an effect on NOx emissions. This was conducted to optimize the coal blending ratio and gas reburning technology for NOx emission reduction and quantify the NOx reduction by the two methods. Blending sub-bituminous coal reduced the unburned carbon (UBC) content, because of its high volatile matter content. Moreover, NOx emissions decreased as the ratio of sub-bituminous coal increased. In terms of the reburning effect, although UBCs increased with the addition of methane, NOx emission decreased by up to 96.05 %. The conversion ratio, defined as the NOx formation ratio of the total fuel N injection, was used to separate the NOx reduction effects of the two methods. Thus, gas reburning in the ammonia co-firing system of coal-fired power plants can significantly reduce NOx emissions.

Optimizing biomass supply for cofiring at power plants to minimize environmental impact: A case of oil palm empty fruit bunches in West Java

This study addresses the supply flow optimization to reduce global warming in a cofiring system, using the example of oil palm empty fruit bunches converted into pellets for use in power plants in Indonesia. Four oil palm mills, seven pellet plants and five coal power plants in the West Java Region were considered in this study to select the optimal supply chain. The study was performed using a life cycle assessment (LCA) for evaluating impact of single firing of coal and linear programming (LP) for optimizing the impact reduction of cofiring of coal and pellets. Our study indicates that the optimal environmental reduction can be achieved by constructing six of the seven pellet plants, which can substitute up to 1 % of the coal supply in five power plants. Accordingly, the emissions could be decreased by an average of 0.018 kg CO2eq/kWh for the power plants, which is equal to 0.2 Mt CO2eq/y or a 1.57 % reduction per year. By varying the emission factor of the pellet plants, our analysis showed a tolerable range in which the supply would not be affected. The sensitivity analysis at a 1 % cofiring rate showed that the increase in biomass supply from the oil palm mills had the highest reduction, whereas the reduction in transportation emissions provided much less impact. By adjusting the cofiring rate, the impact would not change after the 3 % cofiring rate because of the limited availability of Empty Fruit Bunch (EFB) feedstock. However, if sufficient supply could be provided, the environmental impact would be further reduced significantly. Furthermore, the scenario expansion indicated that only three pellet plants would be required for the minimum economic scale of production, although the environmental impact increased by 0.47 % compared to using six pellet plants. Therefore, this study can be used to determine the optimal supply chain scenarios by constructing an appropriate number of economically feasible pellet plants according to the biomass demand and cofiring rate of the power plant.

Impact of Biomass Fuel Feeding Ratio in Co-firing Circulating Fluidized Bed Boiler: A Computational Fluid Dynamics Study

Nowadays, our global population is on a notable rise, coupled with an annual surge in energy consumption. The prevailing reliance on fossil fuels, especially in electricity generation, has significantly contributed to environmental pollution and exacerbated global warming. The circulating fluidized bed, distinguished for its continuous operation and effective heat transfer in the combustion chamber, emerges as a prominent boiler type. Furthermore, the use of biomass fuel, recognized for its renewable and environmentally friendly characteristics, presents an attractive option. Hence, exploring a co-firing system incorporating both coal and biomass as fuel feeds for the boiler holds promise, necessitating optimization for efficient energy production and reduced gas emissions. This study employs computational fluid dynamics to simulate the intricate interactions of solid fuel and flue gas reactions within the boiler, utilizing the two-fluid method for multiphase flow simulation. The circulating fluidized bed boiler in focus employs subbituminous coal, woodchips as biomass sources, and sand as the bed material. Model validation against operational data, including bed temperature, flue gas velocity outlet, and carbon dioxide mass fraction, indicates minimal deviation. Examination of the biomass ratio's impact on fuel feed reveals a reduction in sulfur dioxide emissions with an increasing biomass ratio, attributed to the lower sulfur content in woodchips compared to coal. However, a heightened woodchip blending ratio results in diminished boiler efficiency due to the altered heating value of the mixed solid fuel. The optimized biomass-to-coal ratio in fuel feeding is determined as 59.15%, achieving a maximized boiler efficiency of 82.84% and minimized pollution gas emissions of sulfur oxide and nitrogen oxide in accordance with industrial standards.

Experimental study on the effects of ammonia cofiring ratio and injection mode on the NOx emission characteristics of ammonia-coal cofiring

Ammonia (NH3) cofiring is a promising approach to reduce the CO2 emissions from coal-fired power plants. However, the potential drastic increase of NOx emissions may inhibit the wide implementation of NH3 cofiring. To explore the potential NOx control strategies, the effects of NH3 cofiring ratio (RNH3), NH3 injection mode and overfire air (OFA) rates on the NOx emission characteristics of NH3/coal cofiring are studied in a test furnace that allow for flexible control of the injection positions and combustion environment of NH3. The results show that when NH3 is injected with coal stream (top mixing mode), the NOx emissions increase and then decrease with the increase of RNH3 under all OFA rates. However, when NH3 is fed through the side port of furnace separately (side mixing mode), the NOx emissions exhibit distinct trends under different OFA rates. Under lower OFA rates, the NOx emissions show monotonical decrease with the increase of RNH3, while under higher OFA rates the NOx emissions first decrease and then increase with the increase of RNH3. Consequently, higher OFA rates could produce higher NOx emissions than lower OFA rates. This indicates that air-staging is not always effective in the NOx reduction of NH3 cofiring. Thus, although the side mixing mode of NH3 cofiring exhibits overall better performance in NOx control, caution is needed to accommodate the OFA rate with NH3 cofiring ratio. Although a variety of trends of NOx emissions were observed in this study, the results demonstrate that all these trends are in fact governed by the same mechanism – the competition between the NO-formation and NO-reduction reactions of NH3 in the varying O2 environment in the furnace. By creating appropriate O2 environment in the furnace, the NOx emissions of NH3/coal cofiring could be substantially lower than that of pure coal combustion. The findings of these paper are instrumental in the design and operation of NH3 cofiring system in full scale coal-fired boilers to achieve effective NOx control.

Modeling the co-combustion of bi-fuel blends in a drop tube furnace: A numerical approach

The present study focuses on the numerical modeling of the co-combustion of reject coal (RC) and sal leaves (SL) in a drop tube furnace (DTF) under different conditions, including air-fuel and oxy-fuel environments. The numerical results highlight the significant influence of replacing the N2 atmosphere with CO2 on the temperature profiles of individual fuels and their blends. For instance, when exposed to a 21%O2/79%CO2 atmosphere, Blend SL3 and Blend SL5 experience a decrease in temperature from 1372 K to 1559 K to 1327 K and 1395 K, respectively. Conversely, increasing the O2 concentration to 35% leads to a temperature rise. Furthermore, the combustion analysis reveals that the addition of 10% SL to RC in a 21%O2/79%N2 environment enhances the devolatilization rate from 1.41 × 10−12 kg/s to 1.77 × 10−12 kg/s. Additionally, the char combustion process for all blends is completed closer to the DTF inlet at 0.28 m, compared to 0.32 m for RC alone. These findings indicate that blending SL with RC promotes a favorable combustion process. Moreover, increasing the O2 concentration to 35% in oxy-fuel conditions enhances the temperature profiles. The numerical analysis demonstrates good agreement with experimental data within a range of ±5%–11%. This suggests that the developed model can be effectively utilized for optimizing and designing biomass co-firing systems in industrial applications, considering both air-fuel and oxy-fuel conditions.

Performance analysis of a novel biomass gasification system coupled to a coal-fired power plant based on heat and water recovery

Biomass gasification co-firing is a technology that can be implemented instantly in almost all coal-fired power plants in a relatively short period to reduce the consumption of fossil fuel. Most studies have focused on improving the system according to variations in the gasification conditions, biomass types, co-firing ratio, and boiler loads. However, the whole system process analysis and structural improvement based on the matter and energy of the co-firing system require further investigation. In this study, a novel biomass air–steam circulating fluidized bed gasification co-firing system based on waste heat and flue gas water recovery with different co-firing ratios (approximately 10 %–40 %) was simulated and compared with the original air gasification co-firing system using Aspen Plus software. The impacts of recovered water participate in gasification process and the optimal steam to biomass ratio (S/B) when it varied from 0.5 to 2, on the syngas quality, thermal characteristics of flue gas, recovered water, coal consumption, exergy loss, and efficiency of the system were analyzed. Compared with the air gasification co-firing system, the results showed that the N2 content in syngas reduced from 41.14 % to 28.92 %, and the heat yield of syngas increased by 7.73 %, along with a 110 t/h recovered water surplus at a 40 % co-firing ratio when steam to biomass ratio was equal to 1. The maximum coal saving amount was 2.26–9.11 t/h and the volume of atmospheric pollutants emissions, such as carbon dioxide (CO2), sulfur oxides (SOx) and nitrogen oxides (NOx), reduced by 0.95 %–6.02 %, 0.91 %–0.95 %, and 11.38 %–36.47 % at a co-firing ratio of approximately 10 %–40 %. Furthermore, the exergy loss can be reduced by 4.35 %–10 % with a 1.72 %–3.96 % increase in exergy efficiency, indicating that the new system mode improves the comprehensive performance of the co-firing system.

Technical-economic-environmental analysis of biomass direct and indirect co-firing in pulverized coal boiler in China

An analysis was conducted on two integrated models involving direct co-firing and pyrolysis co-firing systems within a typical 600 MW coal-fired power generation plant. The study assessed the performance of various biomass sources (sawdust, corn straw, and rice husk) using distinct co-firing ratios (5%, 10%, 15%, 20%) across technological, environmental, and economic dimensions. The findings revealed that in terms of thermal and exergy efficiency, the pyrolysis co-firing approach exhibited lower results compared to direct co-firing. Notably, among the biomasses tested, sawdust demonstrated the least impact on boiler efficiency. The CO2 emission was estimated by the Life Cycle Assessment method. The emission of the conventional boiler, along with direct and pyrolysis co-firing of corn straw at a 20% ratio, resulted in CO2 emissions of 1.075 kg, 0.954 kg, and 0.942 kg per 1kWh of electricity, respectively. The different feeding methods were also discussed, providing technically and economically rational options for coal-fired power plants. The economic feasibility of both co-firing systems was also proposed. At carbon tax rates of 410 CNY/t and 464 CNY/t for the direct co-firing and pyrolysis co-firing models respectively, the operational cost of the co-firing systems becomes comparable to that of a coal-fired boiler. However, when the by-product price exceeds 3700 CNY/t, the pyrolysis co-firing model becomes the more economically favorable option. This study primarily concentrates on investigating the real-world application and effective utilization of biomass co-firing systems within the specific framework of China's energy scenario.

Low carbon pathway and life cycle assessment of ammonia co-firing in coal power plants under the context of carbon neutrality

The utilization of ammonia as a partial substitute for coal has garnered considerable attention as a technology for direct reduction of CO2 emissions in power plants. This study has established the model of ammonia co-firing in coal-fired power plants (CFPP), encompassing the whole industrial chain from production to transportation and power generation. The assessment focuses on the economic aspects of ammonia co-firing, with a specific emphasis on the opportunities for harnessing abandoned wind and solar resources, and further considers the life cycle assessment (LCA) of environmental impacts. The results show that in the case of the CFPP, gray ammonia and green ammonia co-firing systems at 30% proportion yield the levelized cost of electricity (LCOE) of 0.042, 0.074, and 0.110 USD/kWh under low carbon emissions, while 0.086, 0.122, and 0.142 USD/kWh under zero carbon emissions, respectively. Notably, when low-cost green electricity derived from abandoned wind and solar resources is utilized for green ammonia co-firing systems, the feasibility of the approach significantly improves. In regions with high carbon taxes or low cost renewable power, the LCOE of low-cost green ammonia co-firing systems will be lower than that of CFPP equipped with carbon capture and storage (CCS) unit, which may be realized in developed countries in the future. By 2030, in areas with the carbon tax price above 83.76 USD/tCO2 under low carbon emissions or the coal price above 165.25 USD/t under zero carbon emissions, the LCOE for the low-cost green ammonia co-firing system (30%) will be lower than that of CFPP and CCS-equipped CFPP. Green ammonia co-firing significantly reduces CFPP carbon emissions compared to gray ammonia co-firing, highlighting its substantial potential. At 30% proportion, the whole industrial chain carbon emissions for the system of CFPP co-firing with gray ammonia (GA) increase by 0.302 kg CO2/kWh (40.38%) and the life cycle GWP value increases by 0.380 kg CO2-eq/kWh (46.15%). In contrast, the system of CFPP co-firing with green ammonia (GE) decreases by 0.203 kg CO2/kWh (-27.09%) and 0.173 kg CO2-eq/kWh (-20.98%). These findings provide quantitative information on the economic and environmental benefits of ammonia co-firing to reduce CO2 emissions in CFPP, informing the low-carbon transition of CFPP with ammonia co-firing technology.

Thermodynamic analysis of ammonia co-firing for low-rank coal-fired power plant

ABSTRACT As one of the largest sources of CO2 emissions, the integration of non-carbon fuels in coal-fired power plants will significantly impact the global decarbonisation strategy. Hydrogen is a potential non-carbon fuel, and ammonia is a promising hydrogen carrier fuel. In this study, the effect of ammonia co-firing in a low-rank coal-fired power plant is thermodynamically modelled and evaluated in Aspen Plus V12.1. The integrated co-firing system is modelled in two different cases. The first case is made to maintain the combustion process, resulting in constant excess oxygen content in the flue gas. The second case is to minimise the fan modification in the power plant by maintaining the maximum air flow rate. The results show that increasing fraction of ammonia reduced CO2 and SOx emissions due to the decreasing coal fraction. NOx emission proportionally changes with the furnace temperature, which increases at constant excess oxygen case and decreases at constant airflow case. It was also shown that both cases’ boiler efficiency is relatively similar on the same ammonia fraction. The thermodynamic analysis provides an initial assessment of the implementation of ammonia co-firing in coal-fired power plants as an effort of decarbonisation in the energy sector.

Behavior of nitrogen oxides in a lab-scale coal ammonia co-firing system

The objective of this study was to determine the ideal coal–ammonia (NH3) co-firing conditions to achieve carbon neutrality and suppress NOx formation. This paper describes the characteristics of NOx formation in NH3–coal co-firing experiments. NH3 co-firing experiments were performed under intensive and air-staged combustion conditions using a 5 kW fluidized bed reactor. Air-staged combustion and divided fuel-injection were effective in suppressing NOx formation during NH3 co-firing combustion. The minimum and maximum NO concentration observed during intensive and air-staged combustion was 70 ppm and 700 ppm, respectively. In addition, some NH3 slips were observed under an NH3 co-firing ratio of 20% or more; however, the reduction effect of NO was observed. The NO concentration increased to approximately 500 ppm under pure NH3 combustion. The simultaneous injection of fuel and oxygen under fuel-rich conditions generated NO and N2O. It increased rapidly under incomplete combustion conditions and increased in proportion to the concentrations of HCN and CO. NH3 co-firing was accompanied by the suppression of NO formation and reduction of N2O and CO2 if injected in consideration of the temperature and oxygen concentration.

Development of a Coal Combustion Model Compliant with the CHEMKIN Format for Use in Co-Firing Analysis with Hydrogen and Low-Carbon Fuels

We developed a simplified coal combustion model that is used in combination with detailed gas reaction models. This model aimed to develop co-firing systems for decarbonized fuels such as coal and hydrogen. The reaction mechanism was described in the CHEMKIN format. We aimed to develop a coal combustion model that is easy to handle even for experts in gas combustion. Based on the experimental results, we modified the following reaction models. (1) Determining the rate constant of NOx reduction by char in the presence of oxygen. (2) Determining the gasification reaction rate constants, especially the rate constant of the steam gasification reaction, from staged combustion experiments. (3) Adoption of a chemical structural model of char based on elemental analysis results. Char was composed of carbon; C, nitrogen; N, and hydrocarbons; CnHm. As a result of the improvement, we achieved the NOx prediction error halved. Improving the calculation accuracy of the coal burnout was most important for improving the accuracy of the gas reactions. If there was an error in the calculated coal burnout due to an error in the gasification reaction, and so forth, the amount of C, H, O, and N species in the coal released into the gas phase would change. These changed the burning conditions, for example, stoichiometric ratio, in the gas phase. As a result, the concentration of radicals such as H, O, and OH changed, causing a decrease in NOx prediction accuracy. We obtained outline of the combustion performances when decarbonized fuel such as hydrogen and coal were co-combusted.

Evaluation of Biomass Development Policies and Strategies for Sustainable Energy

Fossil energy is a threat to Indonesia. The national primary energy mix is dominated by coal, while many foreign investors are aiming for Indonesia's biomass to be used as a power plant. It would be ironic if foreigners controlled it. Policies and regulations in the energy sector are needed for managing and utilizing existing resources. Using descriptive qualitative research methods aims to understand the phenomena experienced by the research subjects. Implementing policies and strategies for developing biomass for sustainable energy is also related to purchasing renewable energy, developing small-scale Biomass Powerplant management in the frontier, outermost and underdeveloped areas, utilization of wastes, municipal waste, and Co-firing systems in existing Coal Powerplant. Policy adjustments are urgently needed regarding using biomass to accelerate the renewable energy mix along the issues to maintain sustainability.

Influence mechanism of ammonia mixing on NO formation characteristics of pulverized coal combustion and N oxidation in ammonia-N/coal-N

Through ammonia-coal co-firing, ammonia as a carbon-free fuel can be used to effectively reduce CO2 emissions in coal-fired power generation. However, ammonia can also act as an N source that allows NOx to be generated through more reaction paths. Therefore, it is highly necessary to explore the N oxidation mechanism in the ammonia-coal co-firing process to achieve low nitrogen combustion. In this study, the N oxidation mechanism in the ammonia-coal co-firing process was explored through an experiment with a high-temperature furnace, XPS testing, and calculations based on quantum chemical theory. The experimental results show that both temperature and ammonia mixing ratios have a significant impact on NO formation. When the combustion temperature is 1200℃, the NO yield increases gradually as the ammonia mixing ratio increases from 20% to 40% and then to 60%; when the combustion temperature is higher than 1300℃, the NO yield increases first and then decreases as the ammonia mixing ratio increases. In addition, the XPS testing demonstrates that the content of char-N resulting from ammonia-coal co-firing at 1200℃ is higher than that resulting from pure coal combustion at 1200℃. This indicates that the N atoms in ammonia can be adsorbed or embedded in char. The theoretical calculations at the molecular level further reveal that the amino groups in the ammonia-coal co-firing system can be oxidized to produce NO, NO2, and HNO via different paths. Both the experimental data and the theoretical calculations confirmed that NO is the main oxidation product. Moreover, the amino groups can stably exist on the char surface under the effects of different adsorption mechanisms, which is consistent with the characterization test. This work lays a foundation for deepening the understanding of the N migration and transformation mechanism in ammonia-coal co-firing. It provides theoretical support for developing methods to ensure low nitrogen combustion in ammonia-coal co-firing.

Engineering And Economic Analysis of Sawdust Biomass Processing As A Co-Firing Fuel In Coal-Fired Power Plant Boiler Pulverized Coal Type

One type of alternative fuel that has the potential to be developed and can contribute significantly to the NRE mix is biomass. The significance of the energy mix is obtained from the use of the co-firing system at the Coal-Fired Power Plant (CFPP) by mixing coal fuel with biomass such as sawdust. Sawdust biomass as cofiring material for CFPP is very efficient because it has energy content and availability that is easy to manage. The aim of this research is to make technical and economic analysis of sawdust biomass as solid fuel for pulverized coal CFPP Co-firing type boiler. The research stages are mapping the potential of sawdust biomass to determine the availability of potential biomass around the location of the co-firing, analyze the technical side and specifications contained in sawdust biomass raw materials to determine the suitability or feasibility of pulverized coal type CFPP specifications, and analyze the economic feasibility of developing sawdust biomass processing technology to determine the cost of production of sawdust biomass so that later it will not have a technical and financial impact. The results of the economic analysis show that the sawdust biomass production business is feasible with NPV parameters > IDR 5,252,097,371, IRR=11.1% and payback period=7.7 years. Provided that if the PLTU Rembang buys biomass at a price of Rp. 862,730/Ton. Sensitivity analysis is used to determine the steps to optimize the adjustment of the ability to purchase biomass from CFPP Rembang where the reference limit for the highest reference price for biomass is IDR 782,006. Efforts that can be made to adjust the ability to purchase biomass from the CFPP Rembang include increasing the yield by 20% or reducing the price of wood by 20%.

China’s coal power decarbonization via [formula omitted] capture and storage and biomass co-firing: A LCA case study in Inner Mongolia

In this study, a membrane-based CO2 capture and storage (CCS) chain and a co-firing system of coal and biomass were virtually implemented in an existing coal power plant in Inner Mongolia. Three life cycle assessment (LCA) models were developed to evaluate the environmental performance of the power generation system under business-as-usual (BAU) conditions and with the implementation of the selected technologies. The CCS system reduced CO2 emissions from the power plant by about 90%, but significantly increased upstream emissions, limiting the LCA mitigation potential to 37%–48% of the 1.14 kg CO2/kWh estimated for the BAU scenario. Combining biomass co-firing with CCS achieved negative emissions from the power generation stage and reduced the total CO2 emitted under the LCA scope by 57%–67%. However, both technologies had negative impacts on the local environment, which were quantified by a range of indicators such as eutrophication potential (+13%–37%), toxicity for both aquatic (+12%–33%) and terrestrial (+35%–68%) ecosystems, and consumption of freshwater (+46%–61%). The major factors preventing a more significant mitigation of CO2 emissions and shifting the environmental burden to local ecosystems were the increased electricity and coal consumption for implementing CCS and the reliance on diesel and artificial fertilizers in the biomass supply chain.

Evaluation of cofiring application in power plant’s coal combustion

Steam Power Plant (PLTU) is a power plant that uses coal as an energy source to generate electricity. Burning coal to produce energy will produce residues in the form of carbon dioxide (CO2), carbon monoxide (CO), nitrogen oxides (NOx), sulfur oxides (SOx), as well as bottom ash and fly ash which is harmful to health and the environment. To reduce pollutant emissions, RS-PLTU has implemented a co-firing system using sawdust. After 8 months of testing, it was seen that there was a decrease in exhaust emissions which could be monitored from CEMS. The total use of sawdust was 10,313.9 tons, which was only 0.54% of the initial consumption target. While the total KWh green produced is 11,108 MWh. The sawdust used comes from the waste from the local wood industry to build the local people’s economy.

Study of distillation waste by clove for alternative fuel power plant: A review

Today, fuel source energy is increasing demand in Indonesia, such as petroleum and coal. Fuel source energy is exhausted and cannot be renewed, therefore renewable energy is one solution for highly energy demand. Innovations of renewable energy like as biopellet from clove leaf refining waste is important for fuel power plant in Indonesia. This research is discuss about characteristics and quality of biopellet from clove leaf refining waste for alternative fuel in electricity generation. The clove leaf is dried up to moisture content from 15% to 30% then made of mesh size 20 and 40 with a milli hummer. then the clove leaf powder was mixed with glue or molasses with a ratio of 80% powder and 20% molasses then printed. Heated of temperature is 90°C, the second specimen is 110°C and the third specimen is 130°C, after it has reached the specified temperature the powder in the mold on the press or pressed with a pressure of 93 kg / cm2. The specimen have been printed and pressed for about 20 minutes. Biopellet can be an alternative fuel solution in Co-firing systems with coal that has been this is the main fuel for steam power generation.

The potential oxidation characteristics of CaCr2O4 during coal combustion with solid waste in a fluidized bed boiler: A thermogravimetric analysis

CaCr2O4 (Cr (III)), mainly generated through the decomposition of CaCrO4 (Cr (VI)), is a significant intermediate for toxic Cr (VI) formation during solid fuel combustion. In this study, the formation, oxidation and sulfation kinetics of CaCr2O4 were analyzed to forecast the potential of CaCr2O4 oxidation during co-firing of coal and solid waste in a circulating fluidized bed boiler. The results indicated that the formation and oxidation of CaCr2O4 were fitted to a single step nucleation and growth model while CaCr2O4 sulfation was fitted to a shrinking core model. CaCr2O4 formation through CaCrO4 decomposition was favored in oxygen-lean atmosphere and considerably suppressed in the presence of oxygen. In contrast, CaCr2O4 oxidation was mainly determined by the contacts between CaCr2O4 and CaSO4/CaO, which influenced not only oxidation rates but also the product species. Moreover, the oxidation reactivity of CaCr2O4 was higher in the presence of CaO than that of CaSO4. On the other hand, CaCr2O4 sulfation can occur more easily than CaCr2O4 oxidation, the reaction rate of which was deeply affected by sulfate product layer. Findings in this study suggested that spraying calcium in furnace for desulphurization may increase the risk of CaCr2O4 oxidation. Measures including the adjustment of Ca/S ratio in blended fuel (with added limestone) and operating conditions (such as temperature and local atmosphere) in co-firing system could be taken to control CaCr2O4 formation and oxidation.