Circulating Fluidized Bed Boiler Research Articles

Application of polymer concrete containing industrial bottom ashes in footing plates for energy poles

The paper presents a procedure of preparing, molding and testing polymer concrete containing 10 – 60% of bottom ash from power plant fluid circulating fluidized bed boiler (CFB)– the rest of the filler was a standard sand. The tests of static bending and mass changes after exposition to acid, base and salt were conducted. Also mass changes after freeze-thaw tests were registered. The tested polymer concretes showed no problems during manufacturing procedures. Compositions containing 10 - 20% by weight of the ash showed higher flexural strength than polymer concrete containing 100% sand and it was about 35 MPa. Relatively small changes in mass (less than 0.5% excluding base exposition for which it was less than 3%) caused by environmental factors, in general consistent with theoretical predictions, allow us to assume that the tested materials will meet the strength requirements for the footplates. It is studied in second part of the set. According to the environmental resistance and description of a whole designing and production process. It was found that the concrete containing 10%wt of the ash is optimal material for producing the plates. It has showed the best resistance to environmental aging from all tested concretes. The designed mold system is simple and reliable - it is applicable for serial production of the plates in industrial conditions. Visual quality of the produced plates was very good. In general, polymer concrete once again turned out to be very good material, applicable in various elements for construction industry.

Optimization of Injection Source Settings for SNCR Numerical Simulation of Low-Water Content Biomass Boilers with Blending.

In order to control NOx emissions and meet China's ultralow emission standards, a numerical simulation based on the computational fluid dynamics (CFD) approach is performed for the optimization of the reductant injection volume, number of injection sources, distribution, and injection direction for the flue gas denitrification process of a circulating fluidized bed boiler (CFB) blended with low-water content biomass in a 168 MW unit of a thermal power plant. Using the target power plant boiler entity as a template, a simplified geometric model is established, 1:1, and the mass fractions of each flue gas component set by the inlet boundary conditions are O22, H2O11.6, CO216.2%, and NO0.05%(about 134 ppm), and the reduction reactions under different optimized conditions are numerically simulated using the SNCR model in ANSYS Fluent 2021 R1. The simulation results under each condition were analyzed. The results show that the optimal ammonia-to-nitrogen ratio should be taken as NSR = 1.25, the denitrification efficiencies of 81.00, 81.63, and 82.74% at the three outlets are high, and the ammonia escapes of 1.76, 2.08, and 9.42 mg/s are within a reasonable range; increasing the number of injection sources can significantly reduce the disturbance of the flue gas flow field by reductant injection; the direction of injection is parallel to the direction of the flue gas flow, and the line of the injection source is orthogonal to the direction of the flue gas flow, which is conducive to the mixing of the reductant and flue gas; the optimized boiler denitrification efficiency reaches 74.2%, meeting the ultralow emission requirements of nitrogen oxides and ammonia escape.

A method for measuring the solid circulation rates of CFB boilers based on the particle flow-around principle

The solid circulation rate (Gs) is a key parameter for the design and operation of a circulating fluidized bed (CFB) industrial equipment, while the detection and measurement of the Gs value in an actual industrial CFB equipment remains difficult. To fill this gap, a method for the Gs measurement based on the flow-around principle was proposed in this study. The mathematical model for the signal transformation was established along the path “detected strain value – impact force – particle velocity – Gs value”, and the corresponding measurement device was also developed. The performance of the Gs measurement device was quantitatively validated in cold-state experiments and semi-quantitatively verified in an industrial trial in a CFB boiler. The results of a theoretical analysis indicate that the detected strain linearly increased with the impact force received by the intrusive spherical obstacle, and the slope coefficient was determined as per the experiment. The correlation of the impact force to the particle flow velocity was proposed and fitted using the experimental data. The computational particle fluid dynamics method was applied to simulate the particle flow field in the standpipe of the CFB boiler to determine the installation location of the Gs measurement device. The lab-scale cold-state experiments showed that the relative standard uncertainty of the Gs measurement using the device built in the present study was less than 2.0 %. This device was then applied in an industrial trial in a 116 MWth CFB boiler and the results proved the feasibility and applicability of the proposed Gs measurement method.

Combustion characteristics of low-quality lignite for different bed material sphericities in a circulating fluidized bed boiler: A numerical study

This study delves into the combustion behavior of various lignite types within a circulating fluidized bed boiler (CFBB), with a primary focus on the impact of different bed material sphericity ratios (0.5, 0.7, and 0.9). Utilizing bed material with a sphericity ratio of 0.9 sourced from the Çan power plant and verified through experimentation, the research reveals several key findings. Notably, furnace temperatures tended to rise with higher sphericity ratios, albeit with variations between lignite types, particularly highlighting the complexity of this relationship in the case of GLI-Tunçbilek lignite. Pressure levels in the combustion chamber remained consistent across different sphericity ratios, indicating minimal influence on pressure dynamics. Improved combustion efficiency, especially at the bottom of the boiler, was observed at lower sphericity levels (0.5 and 0.7) for Çan lignite, as reflected in CO2 mole fractions. While NOx emissions generally decreased with lower sphericity, the sensitivity to sphericity varied by lignite type, with Ilgın lignite showcasing low NOx but high SO2 emissions, underscoring the intricate interplay between lignite properties, sphericity, and emissions. Overall, this study advances our understanding of CFBB combustion dynamics, offering insights valuable for optimizing performance and emissions control, particularly in lignite-based power.

An Improved Data-Driven Integral Sliding-Mode Control and Its Automation Application

Circulating fluidized bed (CFB) boilers are widely used in industrial production due to their high combustion efficiency, low pollutant emissions and wide load-adjustment range. However, the water-level-control system of a CFB boiler exhibits time-varying behavior and nonlinearity, which affect the control performance of the industrial system. This paper proposes a novel data-driven adaptive integral sliding-mode control (ISMC) method for the CFB control system with external disturbances. Firstly, the scheme designs a discrete ISMC law based on the full-format dynamic linearization (FFDL) data model, which is equivalent to a nonlinear system. Furthermore, a new reaching law is proposed to quickly drive the system state onto the sliding-mode surface. The improved ISMC control scheme only utilizes the input–output data during the design process and does not require model information. After theoretically verifying the stability of the method proposed in this paper, it is further applied in MIMO systems. Finally, the control and practical effects of this method are evaluated by using the DHX25-1.25 CFB boiler installed in the special-equipment testing center. The experimental results show that, compared with the traditional sliding-mode control (SMC) and model-free adaptive-control (MFAC) methods, the improved control method can quickly track the given signal and exhibit resistance to noise interference. Furthermore, it can rapidly respond to changes in the working conditions of the CFB system.

Machine Learning Aided Numerical and Experimental Investigation of Hydrodynamic Performance in the Circulating Fluidized Bed Boiler

Abstract This study attempts to illustrate the benefits of integrating the concepts of machine learning algorithms with the field of thermo-fluidic applications. The current work is aimed at identifying effective or significant hydrodynamic input parameters, which are capable of deriving full benefit of fluidization that could yield a better circulating fluidized bed (CFB) furnace design using the Apriori algorithm. For this, historical datasets from the literature are collected and pretreated based on the design under observation. Association analysis performed by this Apriori algorithm measures the comparative strength of parameters under consideration. Also, this algorithm is capable of identifying the right combinations of parameters that can produce maximum fluidization performance. The end results suggested by this Apriori algorithm are validated using the computational fluid dynamics package. For this, the transient behavior of a scaled-down (1:20) reactor model of a real-time industrial CFB boiler is simulated using ansys fluent 18.0. In specific, the effects of fluidizing velocities, inventory heights of the bed, and particle sizes recommended by the Apriori algorithm are investigated. Here, the effects are assessed in terms of volume fraction distribution and axial velocity profile distribution profiles. From the results of simulations, it was clearly found that 2 m/s inlet velocity produced good circulating fluidized bed patterns on a bed inventory height of 0.5 m for a mean particle size of 200 µm. The results obtained from the simulations are once again validated visually against snapshots obtained during real-time laboratory fluidization experimental runs. Among all the cases of comparisons, the best agreement is demonstrated by Apriori algorithm compared to the numerical and the experimentally obtained results. Also, it is found that the manual time taken to identify the right combinations of parameters is drastically reduced by this method compared to conventional optimization algorithm and trial error methods.

Numerical and experimental investigation of co-combustion of chicken manure and lignite blends in a CFBB with novel compact combustion chamber

Increasing worldwide demand for chicken and chicken products has led to increased production of chicken manure. Therefore, chicken manure has an important application potential in the energy industry. This study aims to dispose of chicken manure, which is harmful to soil and groundwater, for thermal energy purposes and to reduce the emissions of lignite coal. For this purpose, it concerns the design and manufacture of a Circulating Fluidized Bed Boiler (CFBB) with a novel combustion chamber for burning chicken manure (CM) and lignite (L) fuels and their mixtures. The combustion behaviors and contaminating emissions of the mentioned fuels in such a CFBB are investigated experimentally and numerically. Emissions of major gaseous pollutants, including CO, SO2 and NO, and the temperature distribution throughout the combustion chamber are measured during the tests. Experimental results show that increasing the amount of CM in the mixture increases CO and reduces SO2. For this condition, NO emission either increases or decreases. According to the numerical results, the temperature of the combustion chamber decreases with the increase of the CM fraction. In the CFBB, the CO emission decreases in the CM fraction up to 25 %, while it increases in the CM fraction above 25 %. For increasing CM fraction, NO emission decreases in the cyclone while it increases in the evaporator. In the experimental and numerical results, the CO2 emission for the L, CM and CM fractions are observed to be equivalent to each other. In conclusion, this study clearly shows that in situ burning of chicken manure or lignite and chicken manure mixtures reduces lignite emissions and meets the heat requirement and disposal of waste in chicken processing plants.

Combustion of chicken manure and Turkish lignite mixtures in a circulating fluidized bed

Burning chicken manure (CM) with lignites may be a promising method to ensure waste management. In this study, a circulating fluidized bed boiler (CFBB) system was designed, manufactured, and tested for the disposal of CM in poultry farming. Combustion and co-combustion tests of CM and Kale Lignite (L) were carried out in the CFBB to determine the effect of excess air ratio and CM share in the fuel mixture on combustion efficiency and flue gas emissions. As the CM share in the mixture increased, the combustion efficiency increased from 86 % to 95 %. It was observed that while CO emissions increased, SO2 and NOx emissions decreased with respect to CM share. CO emissions ranged from 726 to 2241 mg/Nm3 for 100%L and between 838 and 2450 mg/Nm3 for 100%CM. The NOx emissions changed between 177.5 and 240 mg/Nm3 for 100%CM; however, it was 276.3 mg/Nm3 for 100%L. While SO2 emissions (average) for 100%L were around 5200 mg/Nm3, as the CM share in the fuel mixture increased, emissions decreased, and when they became zero for 100%CM. CO emissions decreased as the excess air ratio increased. SO2 and NOx emissions increased as the excess air ratio increased in almost all fuel mixtures. This combustion system was proposed for waste disposal, emission reduction, and usage of domestic sources. Photovoltaic panels can support this system and meet farms' operational energy requirements away from the grid. Combustion efficiency can be increased by operating the system at oxy-firing mode instead of air-firing.

TEs enrichment characteristic in different size particulate from coal-fired flue gas: Part 1. Enrichment and leachability

The trace elements (TEs) and particulate matter (PM) emissions from coal-fired power plants have received much concern in recent years due to their harm to human health and the environment, however, the TEs enrichment characteristic in PM and their migration and transformation mechanisms with PM are not clear yet, especially in fine particles. In this work, the enrichment contents of seven TEs Cd, Pb, Mo, As, Ni, Mn, Cr in coal combustion byproducts collected from circulating fluidized bed (CFB) and pulverized coal (PC) boiler were studied to investigate the influence of boiler type on TEs enrichment behavior. The aerodynamic cutting method was used to separate the fine particles PM10 and PM2.5 from bulk fly ash to study the impact of particle size on TEs enrichment behavior. In addition, the modified BCR sequent extraction method was applied to study TEs occurrence forms in different size particles to evaluate their environment contamination risk. The results show that except low volatility Mn, all the TEs are mainly enriched in fly ash rather than bottom slag and gypsum. The coal combustion in PC boiler is more complete so bottom slag in PC boiler commonly has less TEs enrichment content than that in CFB boiler. The volatile TEs including Cr, Ni, As, Cd, Pb are most enriched in PM2.5, while the enrichment contents based on fly ash volume fraction of seven TEs are most in PM50 (for CFB boiler) and PM10 (for PC boiler), since PC boiler has more PM10 volume fraction. Even though the TEs occurrence forms in different size particles are various due to the complexity of TEs combination mechanism with fly ash, the soluble F1 fraction overall exhibits size-dependence and is highest in PM2.5. RAC result indicates that As, Cd, Mn, Ni, Cr have medium environment risks, especially when they occur in PM2.5.

Comparative Analysis of Combustion Characteristics of a CFB Boiler during the Changes Process between High-Rated Loads and Low-Rated Loads

In order to alleviate problems such as large fluctuations in grid load caused by the high proportion of renewable energy, circulating fluidized bed (CFB) power plants undertake the task of rated load regulation. This study discussed the combustion characteristics of a 100 KW CFB boiler during the operation process of varying loads and analyzes the combustion characteristics, load regulation rate and emissions variation law during the operation process of high- and low-rated load intervals. The experimental results showed that under the condition of a high-rated load, the average temperature of each area in the furnace was proportional to the size of the load. Under low-rated load conditions, the temperature change increased first and then decreased with the reduction in load. In the 30% load stage, the lowest temperature in the riser was 740 °C, while the temperature in the loop seal was even as low as 650 °C. The concentrations of O2, CO and unburned carbon mainly depended on the combustion reaction intensity under each load condition, which showed a higher trend at low load (30%). In terms of NOx emission, it was proportional to the load in the high-rated load range. However, the NOx generation at the 30% load was about 30 mg/Nm3(@6%O2) higher than the 50% load. In addition, the regulation load rate (2.5%/min) between high-load conditions exhibited significantly greater than that between low-load conditions (0.78%/min). Therefore, the low-load operation will face problems such as low furnace temperature, uneven gas–solid fluidization, and difficult control of pollutant generation, which need to be paid attention to during operation.

PCDD/Fs, PAHs and HCl emissions from co-combustion of lignite and chicken manure in a circulating fluidized bed boiler with compact refractory casting

Chicken manure (CM) should be used in energy production due to its high production potential for the waste-to-energy approach. Co-combustion of CM with lignites may be a good practice in terms of reducing its environmental impact and the need for fossil fuels. However, the level of organic pollutants originated from CM combustion is not clear. This study investigated the potential of CM to be combusted in a circulating fluidized bed boiler (CFBB) with a local lignite. Combustion and co-combustion tests of CM and Kale Lignite (L) were performed in the CFBB to measure PCDD/Fs, PAHs and HCl emissions. CM burned in the upper parts of the boiler due to its high volatile matter content and low density compared to coal. This caused the bed temperature to decrease with the increase in the amount of CM in the fuel mixture. It was also observed that the combustion efficiency increased as the share of CM in the fuel mixture increased. Total PCDD/F emissions increased with CM share in the fuel mixture. However, all are less than emission limit value (100 pg I-TEQ/m3). Co-combustion of CM with lignite at different ratios did not have a significant effect on HCl emissions. PAH emissions were found to increase with the increase of the CM share when the CM share was more than 50% by weight.

Solids separation efficiency at the outlet of a circulating fluidized bed riser

In a circulating fluidized bed (CFB) fuel converter the outlet geometry plays a decisive role for the solids flow in the circulating loop, thus affecting the mass and heat balances and the conversion process. A Dense Discrete Particle Model (DDPM) framework is used to investigate the solids flow, with model validation against experimental data from a cold model, scaled to represent the fluid dynamics of a commercial CFB boiler operated under hot conditions. Riser outlets with different configurations (L-shape and T-shape) are studied. The results show that the solids separation efficiency of the outlet (and, hence, of the riser) can be related to the Stokes number (Stk, which varied within 0.034–1.24). Decreased outlet area at a given riser cross-section and/or increased distance of the exit window from the top of the riser yield a higher solids separation efficiency. The smaller the Stk, the lower the solids separation in general, and the less it will be affected by the geometrical configuration. The solids flux value did not show any major impact on the solids separation efficiency attained. Finally, an expression for the solids separation efficiency of the riser outlet is derived, covering a range of efficiencies within 0.3–0.9 and yielding an average error of <20% compared to experimental data from literature.

Simulation of gas-solid combustion characteristics in a 1000 MW CFB boiler for supercritical CO2 cycle

Supercritical CO2 (S-CO2) power cycle has become one of the most efficient and low-pollution cycle schemes to improve thermal power generation efficiency and reduce energy consumption around the world. In this study, the 3D physical model of a 1000 MW S-CO2 circulating fluidized bed (CFB) boiler with annular furnace is established to simulate the gas-solid combustion process based on the MP-PIC method under the Eulerian-Lagrangian framework. By comparing with the conventional water steam CFB boiler, the S-CO2 CFB boiler has a smooth and stable gas-solid flow pattern with good uniformity of the particle concentration and velocity distribution, indicating that the annular structure and the layout of the heating surfaces is conducive to the gas-solid flow uniformity. The gas-solid phase temperature distributes uniformly basically without sudden rise or sudden drop, and the temperature difference between the solid phase and the gas phase is not large, which reflects the good combustion uniformity of the S-CO2 CFB boiler. Compared with 300 MW and 600 MW S-CO2 CFB boilers, the 1000 MW one shows a higher carbon conversion rate, lower desulphurization effect, and lower nitrogen removal performance with the CO, NO, and SO2 outlet concentration of 0.002%, 5.8 mg/m3, and 125 mg/m3, respectively.

Thermal–Hydraulic Calculation and Analysis on Water Wall System of a 700 MWe Ultra-Supercritical CFB Boiler

Ultra-supercritical circulating fluidized bed (CFB) boiler combustion technology has the advantages of environmental protection and good commercialization. As one of the key aspects in ultra-supercritical CFB combustion technology, the water wall system directly determines whether the CFB boiler can safely and effectively transform heat energy. This paper studies the thermal–hydraulic characteristics of the designed water wall system of a 700 MWe ultra-supercritical CFB boiler, the largest one that will be built next year. At four loads of the water wall system, hydrodynamic parameters are calculated based on the successfully verified mathematical models. The results show that the hydrodynamic characteristics of the system are good. The temperature distribution of the working fluid and metal of the water wall system is acceptable and safe at each load, which can support the technical development and improvement of the 700 MWe ultra-supercritical CFB boiler.

Optimal design and thermodynamic evaluation of supercritical CO2 oxy-coal circulating fluidized bed power generation systems

Replacing the steam Rankine cycle with the supercritical CO2 Brayton cycle (sCO2 cycle) has been demonstrated to be an effective way to improve the efficiency of oxy-coal power plants. The present work focuses on the optimal design of the sCO2 oxy-coal circulating fluidized bed (CFB) power generation systems which so far has not received much attention in the research field. A novel triple recompression sCO2 cycle and a new sCO2 oxy-coal CFB boiler configuration with medium-temperature and high-temperature flue gas recirculation have been proposed and evaluated. With the novel boiler configuration and triple recompression cycle, the system efficiency can be increased by about 1.4% points in comparison to the basic system using the basic recompression cycle and the basic boiler configuration. The influences of the cycle minimum temperature, recuperator pinch temperature difference, furnace inlet oxygen concentration, flue gas recirculation flow distribution and coal itself on the sCO2 oxy-coal CFB power generation system performances were thoroughly investigated. The results show that increasing the minimum cycle temperature and the recuperator pinch temperature difference reduces the system efficiency while increasing the oxygen concentration at the furnace inlet and reducing the proportion of the recirculating flue gas as the primary oxidizing gas can boost the system efficiency. Coal itself also has an impact on the system efficiency due to its properties affecting the cycle efficiency, boiler efficiency and auxiliary equipment power consumptions.

Variations in the physicochemical properties of spent honeycomb V2O5-WO3/TiO2 catalysts from PC and CFB boilers SCR denitration systems

The massive production of spent honeycomb V2O5-WO3/TiO2 catalysts has caused serious environmental hazards. Revealing the physicochemical property variations of the spent catalysts is of great significance to clarify the deactivation mechanism of catalysts and the recovery of the spent catalysts. This study focused on the changes of typically spent catalysts, selected from pulverized coal (PC) and circulating fluidized bed (CFB) boiler deNOx systems, morphologies, pore structure, chemical composition, carrier, and active components properties, etc. The activities of most spent catalysts could be to more than 95% at 300–400 °C after vibration cleaning. The pore blockage caused by fly ash and sulfur deposition is the major deactivation factor of the catalysts from the two furnace systems. The catalysts from CFB furnaces are more easily deactivated, which is owing to they are more prone to occur severe pore structure loss. The transformation of anatase to rutile TiO2 as one of the major factors causing the pore structure loss would form the irreversible deactivation of the catalysts. The valence state of the active component V has shifted. The spent catalysts from PC systems typically exhibit higher V4+/Vn+ ratios. However, those from CFB systems display a noticeable decrease, which may be attributed to the formation of CaWO4, resulting in the destruction of dispersed active sites on the surface. Finally, the deactivation mechanism of the spent catalysts from different furnaces of coal-fired power plants was summarized. This research is beneficial for further modification of SCR catalysts under different application conditions and provides valuable insights into the classification and recycling of the spent catalysts.

One-dimensional numerical simulation of CFB combustion: Improvement of hydrodynamic models for accurate prediction of pressure and particle size distributions

This study aims to improve the accuracy of one-dimensional numerical simulations of circulating fluidized bed (CFB) boilers by evaluating models related to solid properties, such as attrition, fragmentation, cyclone efficiency, and bed material discharge. The study validates models for estimating solids holdup and particle size distribution (PSD) using experimental results from a 12 MWth CFB boiler. The study found that accurate prediction of solid axial holdup and local PSD requires proper consideration of attrition and fragmentation, and the simulation results show that attrition has a more significant effect on numerical analysis performance than fragmentation. By using appropriate values for sand attrition constant (5E-7), char attrition constant (6E-6), and coal:1.5, sand:1.2, and char(ash):1.2 fragmentation constants, the pressure distribution measured from experiments was best predicted. The simulation successfully predicted the particle PSD distribution at a specific location in the CFB boiler and pressure change by height, similar to the experimental results In addition, this study investigated the accuracy of 3D computational fluid dynamics (CFD) simulations using solid properties obtained through 1D simulation as initial conditions compared to those based on experimental conditions. The results revealed that 3D CFD simulations using the solid properties from 1D numerical analysis are more accurate, implying that 1D-3D co-simulation approach is a good strategy to increase the simulation performance.

Emission and Energy Characteristics of the Combination Use of Coal and Biomass in Circulating Fluidized Bed Boilers (CFBB) in Steam Power Plant

Currently there are still many power plants using fossil fuels, including oil, gas and coal to produce electricity. The problem recently received by many developing countries, including Indonesia, is environmental degradation due to CO, SO2 and NOx emissions. Co-burning of biomass with coal is in most countries one of the most economical technologies available today for significant pollutant reduction. This study tested the combined combustion of coal and biomass in a direct co-firing Circulating Fluidized Bed Boiler (CFBB) with two treatments, namely   5 wt% sawdust biomass and 95 wt% coal, 5 wt% woodchip biomass and 95 wt% coal. The results of the two tests were compared with the parameters when using 100 wt% coal. This study aims to (1) analyze the energy produced from burning a combination of coal and biomass, and (2) analyze the emission content, including SO2, CO, NOx. The mixture of coal and sawdust produces 82 MWh of gross electricity, higher than coal and woodchips and requires the smallest amount of fuel, namely 18.7 tons per hour. The 5 wt% woodchip emitted the lowest emissions compared to the other 2 cases, namely 71.5 mg/Nm3 SO2 and 222.4 mg/Nm3 for NOx. The lowest CO emission was issued by a 5 wt% woodchip mixture, namely 4.0 ppm.

Combustion of scrap waste tires of a cogeneration plant

Various fuels can be used in circulating fluidized bed (CFB) boilers. In this study, the thermal and economic performance was investigated for three CFB fuels—heavy fuel oil, coal, and waste tire scraps—used in a cogeneration plant. The plant comprised a CFB boiler, a single-cylinder steam-extraction turbine, and a generator. Tire scrap combustion generated the most power per ton during peak hours: approximately 27.5% more than that generated using heavy oil and 42.3% more than when coal was employed; it also resulted in higher boiler efficiency during peak operation than coal (1.2% higher) or heavy oil (12.6% higher). The net plant efficiency during peak hours was highest for coal (25.09%), followed by tire scraps (23.82%) and heavy oil (18.11%). On the basis of international spot fuel prices, tire scraps were determined to have the lowest cost per kilowatt-hour generated, followed by coal and heavy oil. Using waste tire scraps as fuel can not only reduce pollution but also help hedge against international crises, which can affect energy imports.

An inexact multiple-recourse hybrid-fuel management model with considering carbon reduction requirement for a biofuel-penetrated heating system

In China’s goal of reaching carbon neutrality by 2060, the blending-biofuel-based heating technique is being used to reduce CO2 and air-pollutant emissions in existing district heating systems in northern China. This brings a series of new system components, complex interactions, and multiple-polymorphic uncertainties to the heating systems, making it difficult for the heating-system manager to improve the traditional fuel management mode while considering the demands of society, economy, policy, environment, and system operation. To address this issue, this study proposes an inexact multi-recourse hybrid-fuel management model for a biofuel-penetrated district heating system (BDHS). The model minimizes the total heating cost by optimizing the biofuel blending ratio, coal and biofuel deficit-recourse pattern among different heating sources, and selecting the optimal CO2 reduction mode under uncertainties. An application of the model to a BDHS case in Dalian City shows that the 5% biofuel blending ratio is suitable for both main heating sources and that the 0 deficit of high-quality coal can be up to [2.48, 2.69] × 103 tonne with the “cold-degree” changing from “mild” to “cold”. The results also indicate that the proposed model can ensure biofuels and high-quality coal are not overused or misused, but instead consumed responsibly. Additionally, most of the CO2 produced in the pulverized coal boiler is traded, while most of the CO2 sourced from the circulating fluid bed boiler is treated by the chemical absorption equipment. Finally, the model reveals that a high system cost (up to [84.73, 96.83] × 106 CNY) and low CO2 emission (down to [66.13, 78.07] × 103 tonne) can be obtained at a high thermalization coefficient through the tradeoff analysis.