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Grate-fired boiler is of considerable interest for burning biomass owing to its reduced sensitivity to variations in fuel composition and size. However, grate-fired technology exhibits unsatisfactory performance in terms of combustion efficiency, contaminant emissions, and flame stability. CFD modelling can provide reasonable optimizations to overcome these drawbacks and ultimately achieve clean and efficient energy production. Conventional approach simulates the fuel-bed and freeboard combustion separately using an in- and over-bed coupling procedure, where data of the gases leaving from the packed-bed top and the radiative heat flux emitted by the high-temperature flame onto the bed cannot be interacted in real-time. This may cause distinct deviations in the calculations. In this paper, a three-dimensional (3D) full-scale integrated model is developed for the simulation of grate-fired boiler, in which the intensive combustion of both the freeboard and fuel-bed is solved in one scheme using the Eulerian-Lagrangian method. The gas phase is considered as a continuous medium and calculated by the Eulerian model, while the solid particles are considered as a discrete phase and tracked via the Lagrangian method. The reliability of the model is well verified through various field measurements and observations. Results shows that the key parameters are non-uniformly distributed along the grate width, i.e., the aerodynamic and combustion environment is poor at the vicinity of water-cooled walls compared with that at the furnace center. This results in a significant lag in volatile gases release and char oxidation near the water-cooled wall on both sides, which finally causes obvious differences in the distribution of temperature and species. For instance, the peak of CO concentration at the center is 12.6 % at 3.3m from the feed entrance, while that near the water-cooled wall is 8.6 % around 3.5m. The char burnout ratio in the bottom ash can be accurately calculated by this model, with a negligible relative error between the simulation of 81.97 % and the measurement of 82.50 %. It also provides a novel method for the calculation of fly ash particles by using size-grouped and non-spherical particles. Small-size particles in the vicinity of the feed inlet, as well as a part of the particles burning at the end of the grate are entrained into the freeboard by the primary air supplied beneath the grate and the high-momentum secondary air on the bed top. This model can provide valuable theoretical guidance for optimizing the refined distribution of fuel and air in grate-fired power plants and mitigating irregular deposition (corrosion) on heat exchangers and water-cooled walls caused by fly ash. [Display omitted] • An integrated model is developed for accurate modeling of travelling grate boiler. • Real-time mass and heat transfer between the fuel bed and freeboard is achieved. • Key parameters are found to be non-uniformly distributed along the grate width. • Non-spherical and size-grouped particles are used to better represent agricultural straw. • A novel method for calculating fly ash in grate-fired boiler has been developed. [ABSTRACT FROM AUTHOR]

The interaction between volatile and char is widespread in combustion. The effect of this interaction on the conversion of fuel-N to NO x is significant, but the mechanism remains to be comprehensively unveiled. Thus, in this paper, the NO and N 2 O conversion of nitrogen-containing biomass models (glutamate, glycine, phenylalanine) during combustion at high temperatures (800–1500 °C) is investigated using two combustion modes, separated combustion (in which volatile and char are burned separately) and coupled combustion (in which volatile and char are burned simultaneously), in an O 2 /Ar atmosphere. A new pathway for N 2 O formation resulting from the interaction between volatile and char is identified. At low temperatures, this interaction facilitates the conversion of fuel-N to N 2 O. For instance, during the separated combustion of glutamate at 800 °C, the conversion rates of fuel-N to N 2 O and NO are 26.3 % and 20.4 %, respectively. However, in coupled combustion, these conversion rates shift to 48.1 % for N 2 O and 3.6 % for NO. At high temperatures, this interaction promotes the conversion of fuel-N to NO. For instance, during the separated combustion and coupled combustion of glutamate at 1500 °C, the conversion rates of fuel-N to NO are 6.2 % and 16.6 %, respectively. Similar patterns are observed for the other two amino acids. In both combustion modes, the co-firing of cellulose, lignin, and hemicellulose with glutamic acid significantly suppresses the production of N 2 O. The conversion rate of N 2 O decreases by about 7 %–10 %, while the impact on NO release shows either a suppressive or promotive effect in different temperature intervals. These results play a crucial role in the development of efficient and clean combustion technology for biomass. [Display omitted] • A novel N 2 O formation pathway from volatile-char interaction has been identified. • Volatile-char interaction enhances NO formation at 1300–1500 °C. • Accurate volatile-NO/N 2 O and char-NO/N 2 O contributions were determined. • Co-firing with cellulose, lignin, and hemicellulose inhibits the formation of N 2 O. [ABSTRACT FROM AUTHOR]

Grate boilers are widely applied in biomass combustion for heat and energy generation. However, grate-firing systems often suffer from low efficiency and high emission. Computational fluid dynamic (CFD) becomes increasingly popular as a flexible method to obtain the detailed combustion behaviors in the furnace, and to optimize the performance of existing grate boilers. This paper presents efforts toward a reliable baseline CFD model for an industrial biomass-fired grate boiler, where the structure of the fuel-bed was sufficiently considered. The combustion performances in the furnace were investigated experimentally and numerically by coupling the fuel bed and freeboard, to clarify the impact of bed structure on the simulation accuracy. Results show that when the bed structure has been taken into account, the predictions are in better agreement with the various measurements, as the deviations between them are all within 10 %. Moreover, the flame center drops, the total heat transferred to the water-cooled walls increases, and the residence time of flue gas is greatly prolonged from 2.76 s to 3.90 s, resulting in a distinct difference of the temperature and species patterns in the freeboard. The simulations will provide valuable theoretical guidance for the accurate modeling of grate-fired boiler. [Display omitted] • A baseline model is proposed for accurate modeling of biomass-fired grate boiler. • Effect of fuel-bed structure on the simulation of grate boiler is clarified in detail. • Bed structure greatly affects the predicted temperature and species patterns. • Flue gas residence time and heat transfer are also highly impacted by bed structure. [ABSTRACT FROM AUTHOR]

Biomass fuel is an environmentally friendly renewable energy source and carbon-neutral (non-fossil) fuel alternative. To facilitate its wider uptake, significant efforts are undertaken to model and experimentally study biomass combustion processes, in both industrial-scale (grate fired) and small-scale (lab-scale) combustors. In many studies, the core aim is to better understand the relationship between thermal conversion processes (drying, pyrolysis, char conversion) and their interrelationship to combustor performance (efficiency, emissions, process temperatures, scale formation, and instabilities). However, due to the complexity of solid fuel (particle) conversion and fuel bed behaviour, precise modelling of all aspects of biomass fixed-bed combustion is not readily achievable. Despite the existence of excellent experimental and modelling studies on numerous aspects related to the characteristics of forestry derived biomass fuels and their combustion, research in this field is challenging. Complications arise from the multitude of fuels used, the varying geometries and combustor configurations investigated and the different modelling methodologies adopted to resolve steady-state and transient operation. The literature includes works on various aspects of biomass combustion, including that undertaken in fixed-beds. However, whilst these works are valuable, they do not sufficiently cover the methods and fundamentals to model direct thermal conversion, at the bed and particle-level. The aims of the present study are to provide a fundamental overview of the methodologies employed in the modelling of laboratory-scale fixed-bed combustors. The paper also includes treatment of the fundamental thermo-physical fuel characteristics which need to be considered when undertaking macro-scale (bed-level) modelling. The paper concludes with summary observations in relation to the modelling of fixed-bed combustion as well as some opportunities which warrant further research and the challenges to be overcome. [ABSTRACT FROM AUTHOR]

The paper presents new approach in reducing of the CO emission in exhaust gases from small-scale wood pellet boilers. The results are obtained by control of the airflow to the boiler using a model-based nonlinear predictive controller. The complex-structure nonlinear model designed, and simplified to the nonlinear block-oriented Hammerstein system. Finally, the Hammerstein system is used to design the nonlinear predictive controller of the combustion process. The effectiveness analysis of the designed control algorithm under operating conditions at nominal heat power shows that 1) the airflow changes to the boiler is crucial for the CO concentration in the flue gasses and 2) accurate control of the airflow may lead to a significant reduction of the CO emission without any changes of the boiler design. The paper shows that reducing CO emissions from small-scale wood pellet boilers decreased by 35–50% of the original value with low implementation cost to fit industrial scale. • Complex-structure nonlinear model of small-scale boiler for biomass combustion. • Air flow nonlinear extended horizon predictive controller based on Hammerstein model. • CO emissions is decreased to 35–50% in actual operating conditions. • Low-cost modifications, easily implemented to commercially available boilers. [ABSTRACT FROM AUTHOR]

Engineering efforts to handle contemporary energy supply challenges and mitigate pollutant emission lead towards more complicated systems. Power plants are supplementing with additional processing units, alternative production modes and higher level of automation. Wind and solar sources, biomass combustion, gasification, carbon capture and storage (CCS), and cogeneration have appeared as important players in the energy systems. The increasing complexity comprises a risk that the systems become less manageable and less stable than currently. Traditional steady-state engineering methods cannot fully address these challenges that are inherently dynamic in their nature. Dynamic process simulation appears as important tool to the systems design and optimisation tasks. A large variety of dynamic process modelling and simulation approaches has been presented recent years. This paper presents a brief review of methods and simulation packages that are generally applied for studying energy systems' transient behaviour. A CCS capable power plant is presented as an example of utilizing dynamic process simulation for virtual evaluation of a novel electricity production concept. The modelling was performed using two simulators Apros and Aspen Plus Dynamics, which were linked together for dynamic simulating the full chain of cryogenic oxygen distillation, oxy combustion, turbine islands and carbon dioxide purification and liquefaction operations. • Dynamic simulations for design and optimisation of contemporary energy systems have been reviewed. • A case study for evaluating oxy combustion CFB boiler cycle with carbon capturing is presented. • Co-simulation with two dynamic process simulation software: Apros and Aspen Plus Dynamics were shown. • Flexibility aspects of oxy combustion power plant are discussed. [ABSTRACT FROM AUTHOR]

In this paper, the effect of alkaline-earth metals (AEMs, Ca, Ba, and Sr) on the performance of CuO/ZrO 2 oxygen carriers (OCs) and the hemical looping with oxygen uncoupling (CLOU) process of wheat-derived hydrochars with these Cu-based OCs were investigated. The results showed that after multiple cycles, the crystal phases of modified Cu-based OCs were the same as that of pure CuO/ZrO 2 OC without any interaction between them. Due to the catalytic effects of AEMs, an increase in the decomposition of wheat and hydrochar-235 in modified Cu-based was observed at 500 °C. The combination of Ca and HTC promotes reoxidation, while Ba and Sr inhibit reoxidation. Notably, the Cu-based OCs exhibited moderate agglomeration after 20 redox cycles at 950 °C. The results of the kinetic analysis indicate that the chemical order models and diffusion models can suitably describe the first combustion stage for wheat and hydrochars with Cu-based OCs, respectively. The geometrical contraction model was also found to most suitably describe the second combustion stage of all samples. These results suggest that a combination of hydrothermal carbonization pretreatment with AEMs modification is an efficient approach for CLOU using CuO-based OCs. [Display omitted] • AEMs enhanced the decomposition under 500 °C without interactions with CuO OC. • Simultaneous combustion and reoxidation enhancement of hydrochar-235 was observed. • The reoxidation activity of CuO was improved by Ca but inhibited by Ba and Sr. • Moderate agglomeration of CuO was observed after 20 redox cycles at 950 °C. • The kinetics of biomass combustion was estimated using the Coats-Redfern method. [ABSTRACT FROM AUTHOR]

The co-combustion of raw and torrefied biomasses is recognised as environmental friendly energy conversion. Co-combustion of hard coal with raw biomass has been widely investigated in the literature. In contrast, co-combustion with torrefied biomass has been not particularly investigated. This paper shows the investigations of co-combustion of raw, torrefied biomass and biodegradable waste in bubbling fluidized bed combustor. Two kind of biomass sources (i.e. willow (Salix viminalis), olive oil residue) and waste wood from furniture manufacturing were analysed in terms of fuel feeding rate, CO, SO 2 and NO x emission and ash behavior. The part of a raw biomass was torrefied using a rotary kiln reactor. Hence, the combustion performance of raw and torrefied biomass was compared. The impact of torrefaction on the emission of CO, SO 2 and NO x depends on biomass type. In the case of willow the decrease of SO 2 emission was obtained when the raw biomass was substituted by the torrefied biomass. Additionally, ash fusibility from the raw and torrefied biomass was analysed. It was noticed that co-combustion of torrefied biomass caused increase of ash initial deformation temperature (IDT) comparing to co-combustion with a raw biomass. [ABSTRACT FROM AUTHOR]

Biomass is a carbon neutral fuel and can effectively replace fossil fuels. However, its large scale application is limited by disadvantages such as low calorific value, low energy density and high alkali content. Densification, pyrolysis and adding additives are available methods to upgrade biomass fuels. Nevertheless, emission rules of nitrogen and sulfur oxides in combustion of densified biochar need to be clarified. This paper focuses on the emission and transformation mechanisms of nitrogen and sulfur pollutants during pyrolysis and combustion of biomass with phosphorus based additives by means of thermodynamic calculation and experimental research. The addition of additives promoted the emissions of H 2 S, COS and NH 3 during pyrolysis, so the treatment of H 2 S and COS needs to be considered particularly. During combustion of densified biochar at 1000 °C, increased pyrolysis temperature accelerated SO 2 emissions, while it had no obvious influence on NO emissions. NH 4 H 2 PO 4 accelerated organic sulfur release, NH 4 H 2 PO 4 and Ca(H 2 PO 4) 2 slightly reduced the emission of NO. The maximum values of NO and SO 2 release rates were about 2.81 and 1.55 g/kg, respectively, which were lower than those of most typical fuels. The upgraded densified biochars have benefits such as high calorific value, low melting point and low pollutant emission. • Emission rules of nitrogen and sulfur oxides of densified biochar were studied. • Influences of phosphorus additives on transformation of N and S were studied. • Additives promoted H 2 S and NH 3 release during pyrolysis. • SO 2 and NO emissions of densified biochar during combustion were lower than most fossil fuels. [ABSTRACT FROM AUTHOR]

Interest in circulating fluidized bed (CFB) boilers as a power generation technology has sky-rocketed in recent years because of several advantages this technology offers over conventional boilers, such as increased gas-solid mixing, which results in higher combustion efficiency and the ability to use lower rank fuels. CFB combustors are operated at lower temperatures than conventional thermal power generation combustors, thus reducing NO x emissions, while SO 2 emissions can be conveniently controlled through the addition of Ca-based sulfur sorbents within the combustor. This paper summarizes the modeling effort on a 50 kW th CFB combustor designed, built, and operated at CanmetENERGY in Ottawa, Canada. The numerical model employs the multiphase particle-in-cell (PIC) approach in the open-source Multiphase Flow with Interphase eXchanges (MFiX) Software Suite. The MFiX-PIC model parameters for the simulation are tuned against cold-flow experiments from CanmetENERGY using olivine sand as the inert bed material. It is shown that for the relatively coarse fluid meshes and large parcel sizes necessitated by the scale of the simulation, filter size dependent corrections to the drag law must be incorporated to ensure accuracy of the simulation results. The validated cold flow model is extended to simulate reacting flow with torrefied hardwood as the feedstock and to validate the combustion reaction scheme. The species concentrations at the riser outlet are compared against CanmetENERGY's experiments and show satisfactory agreement. The simulations demonstrate the ability of MFiX-PIC to accurately capture both the physics and chemistry of a CFB combustor at bench scales, which can be further extended to pilot- and industrial-scale systems. • MFiX-PIC is employed to model the 50 kW th circulating fluidized bed at CanmetENERGY. • Calibration of PIC for a large-scale application is discussed in detail. • Filter size dependent corrections are incorporated to the drag law for accuracy. • Combustion reaction scheme is developed and validated against experiment. • MFiX-PIC model accurately captures both physics and chemistry of the CFB combustor. [ABSTRACT FROM AUTHOR]

This paper is focused on aerosol fine particle release during the thermal decomposition of beech wood samples with identical mass under an oxidizing and inert atmosphere. This thermal degradation of wood is a significant part of the biomass combustion and pyrolytic process. This contribution focuses on nanoparticles emission with specifying sizes and concentrations in the range of 18–545 nm during thermal degradation processes and determining correlations between individual thermal degradation processes of a wood sample with the same weights but with different heating rates. The flue gases' chemical composition was simultaneously analyzed using a quadrupole mass spectrometer during the thermal degradation process. The weight loss of the sample and its derivation were monitored using a thermogravimeter. This combination made it possible to identify the ranges with the highest particle emission concerning the wood sample and the sample's heating rate. The fine particle identification apparatus uses a Scanning Mobility Particle Sizer and a condensation particle counter. This experimentally obtained data were then compared with the numerical model CPD-Bio. In this case, the comparison was focused on the prediction of the temperatures of the individual pyrolysis stages, at which gaseous products and especially tars are formed. • Thermal degradation of beech induces dominantly particles in size 130 to 230 nm. • CPD-Bio calculation model is suitable for particulate mass identification of biomass. • Mass yields of tars serve as precursors for aerosol particles. • Particle number concentration increases with increase of heating rates. [ABSTRACT FROM AUTHOR]

In this paper, we developed a detailed process model to evaluate the potential of heat generation from biomass combustion in a CFB (circulating fluidized bed) combustor by coupling Aspen Plus simulator and dedicated FORTRAN subroutines. Mass yields of permanent syngas and solid char are simulated with respect to the pyrolysis temperature by a series of experimental correlations. Particular emphasis was placed on the influence of EOR (excess oxygen ration) upon released emissions and temperature. The parameter of biomass particle size was taken into account to evaluate its impact on combustion parameters and pollutants. To better understand the oxy-fuel combustion, the combustion efficiency (η c ) evaluated as a function of the equivalence ratio and EOR. In order to evaluate the influence of the metal catalysts on the reaction temperature and the concentration of air pollutants, an experimental study of catalytic combustion was also carried out. Model predictions were compared with available data from the literature, which showed fully good agreement. [ABSTRACT FROM AUTHOR]

The benefits of oxygen enrichment have been demonstrated in a variety of industrial combustion applications, but to date no implementation of oxygen enrichment in boilers has been reported, primarily due to their already high thermal efficiencies and a very large scale of such systems, which require significant amounts of oxygen. But recently, oxygen combustion in boilers has become one of the CCS technologies which can be an effective tool for reducing greenhouse gases emissions, and oxygen enriched combustion is suitable for low-calorific fuels, including biomass. This paper analyses the use of oxygen enrichment in a furnace for co-firing of different kinds of biomass with hard coal in terms of emission and burnout impact (LOI). As a part of this research, the effect of injection oxygen mode and total oxygen concentration on the flue gas emission (SO 2 , NO x ) and burnout from co-firing of straw and wooden biomass in different proportions (20% and 40%) with hard coal were studied. The co-firing tests were carried out in an isothermal flow reactor. One of the benefits from the OEA (oxygen enriched atmosphere) technology is more effective separation of CO 2 owing to the higher CO 2 concentration in the flue gas. The additional advantage of the OEA combustion technology in comparison with oxy-fuel combustion is that the OEA process needs lower O 2 purities and therefore it is cost-effective. Experimental tests on co-firing of 20% straw-hard coal blend were conducted in oxygen enriched (up to 25 and 30%) atmospheres with three variants of O 2 injection modes. NO x , SO 2 emissions and burnout for the various atmospheres in the combustion chamber were studied. Moreover, co-firing tests were performed with 40% share of wooden biomass to examine the effect of the biomass share and a type on emission of NO x and SO 2 in OEA. The two O 2 injection modes were investigated. In each case, the emission of SO 2 increases alongside an increase of oxygen concentration in atmosphere. However, the experimental results show that stable and relatively low SO 2 emission and low NO x emission can be achieved for OEA when oxygen is supplied to the primary stream of air. Also, minimal LOI (loss on ignition) is obtained for OEA I+. The supply of oxygen to the secondary oxidizer stream into the burner results in highest NO x emission only in the case of OEA30. It can be therefore concluded that both the oxygen enriched atmosphere and the O 2 injection mode affects NO x emission. [ABSTRACT FROM AUTHOR]

This paper studies the technical, economic, and environmental feasibility of a standalone adsorption cooling system thermally driven by biomass combustion and solar thermal energy. The developed cooling package was benchmarked against a baseline vapour compression refrigeration system, driven by grid electricity and the widely investigated adsorption cooling system driven by solar heat. TRNSYS was utilised to imitate the integrated systems, investigate their year-round performance, and optimise their designs by employing the meteorological data for Rwanda and an existing cold room (13 m2 floor area × 2.9 m height) as a case study. The optimisation study for the system revealed that maximum chiller performance (COP = 0.62), minimum biomass daily consumption (36 kg), and desired cold room setting temperature (10 °C) throughout the year can be achieved if the boiler setting temperature, heat storage size, and heating water flow rate are 95.13 °C, 0.01 m3 and 601.25 kg/h. An optimal PV area/battery size combination of 12 modules/16 kWh was obtained from the economic, environmental, and technical viewpoints. [Display omitted] • A standalone bio-driven adsorption cooling system was developed. • A PV solar system was integrated to drive the system's auxiliaries. • The system's variables were optimised to minimise the cost and environmental impact. • The system's technical, economic, and environmental feasibility were analysed. [ABSTRACT FROM AUTHOR]

The indoor air quality in schools is very important for health and learning abilities of children. The primary indoor CO 2 source in classrooms is the respiration of school building occupants. Also, CO 2 comes from outside as a result of fossil fuels combustion. CO 2 concentration depends on a ventilation rate, size of the classroom, number of occupants and their activity and time they spend in school building. Unfortunately, ventilation rates in schools were not often measured, even in cases when inadequate ventilation caused pupils’ health problems and their absence from school. The increase in indoor CO 2 concentration above the outdoor concentration is considered as a good surrogate for the indoor concentrations of bio effluents. This paper presents the research of ventilation rates in five naturally ventilated schools in urban and rural areas in Serbia during the heating season. CO 2 concentrations were measured outdoor and in three classrooms for five working days, continually. Ventilation rates are calculated based on measured concentrations of CO 2 . The results have shown that classrooms in Serbian schools have inadequate ventilation during the heating period. Mean value of carbon dioxide concentration has often been exceeding 1000 ppm. [ABSTRACT FROM AUTHOR]

Since the formation of gaseous pollutants during solid fuel combustion in circulating fluidized bed (CFB) units, especially under oxyfuel combustion and chemical looping combustion conditions, is an extremely complex process, the development of a simple predictive model of gas emissions is of practical significance. This paper introduces a novel approach based on fuzzy logic (FL), one of the main artificial intelligence (AI) methods, for the prediction of CO 2 , CO, NO x (i.e., NO + NO 2), N 2 O, and SO x (i.e., SO 2 + SO 3) concentrations in flue gases from coal and biomass combustion in various operational sceneries. The simulations are carried out for different combustion environments, i.e., air-firing, oxyfuel, iG-CLC (in-situ gasification chemical looping combustion), and CLOU (chemical looping with oxygen uncoupling), under a wide range of operating parameters. A mixture of oxygen with CO 2 was used for oxyfuel combustion. Three different oxygen carriers (OC) were examined in the study for iG-CLC and CLOU, i.e., ilmenite, copper oxide (60% wt.) with the support of carbonate waste from ore flotation, and copper oxide (60% wt.) with the support of ilmenite (20% wt.) and fly ash. The validation of the model was successfully performed on a complex geometry laboratory–scale 5 kW th Dual-Fluidized-Bed Chemical-Looping-Combustion of Solid-Fuels (DFB-CLC-SF) facility. The gaseous pollutant emissions predicted using the developed model were in good agreement with experimental results. The maximum relative error between measured and predicted by the model emissions was lower than 8%. The proposed method constitutes a quick and easy-to-run technique and a complementary tool compared to the experimental procedures and the programmed computing approach. The developed fuzzy logic-based model of gaseous emissions from advanced combustion (GasAdComb) of solid fuels can be easily applied by scientists and engineers to simulate and optimize coal and biomass combustion processes. • A comprehensive model of 5 kW th Dual-Fluidized-Bed CLC facility was developed. • Fuzzy logic approach was applied in the study. • Air-firing, oxyfuel, iG-CLC and CLOU under a wide range of operating parameters are considered. • The model was successfully validated against experimental data of gaseous pollutants emissions. • The model constitutes an easy-to-use optimization tool. [ABSTRACT FROM AUTHOR]

This paper presents the research on improving combustion of wood and agro pellets in domestic hot water boilers. The novel biomass combustion system concept consisting of rotary burner and two types of combustion intensifiers is proposed, with the aim to allow simple application in the most of existing boilers, as well as to improve the efficiency and emissions to extent the related requirements of the relevant EU standards are met. In this regard, inclusion of the combustion intensifier based on honeycomb structure into conventional combustion system is numerically and experimentally investigated and the most appropriate placement in a furnace found. The results show that, with such implementation of the combustion intensifier, significant reductions in unburned pollutant emissions (CO >40% in case of wood pellets and >30% in case of agro pellets), particulate matter emissions (28–56 mg/m n 3 at 10% of O 2 in dry flue gases) and improvements in combustion efficiency (>2.6–3.7%) can be obtained. A detailed numerical analysis of the subsequent combustion process within the combustion intensifier lead to the novel combustion intensifier design, aimed at lowering manufacturing cost. Preliminary numerical and experimental results indicate similar or slightly less reduction in unburned pollutants of novel design. • Novel combustion system concept for burning wood and agro pellets is presented. • Reductions in CO emissions above 30–40% are obtained. • Reductions in PM emissions for 28–56 mg/m n 3 are obtained. • Increase in combustion efficiency above 2.6–3.7% in case of agro pellets is achieved. • New design of combustion intensifier is proposed. [ABSTRACT FROM AUTHOR]

Currently, 57.4% of the European Union (EU-28) population live in houses which usually need separate boilers to generate thermal energy. The research presented in this paper pertained to a detached house in the north-east of Poland, in which thermal energy was generated over 12 consecutive years by burning wood briquettes. This study analysed the quality and quantity of wood briquettes, energy consumption and cost of thermal energy generation for the house with the use of an automatic biomass burning unit, compared with other types of fuels. The annual consumption of briquette energy was 124.5 GJ year−1. The average annual cost of thermal energy generation for a house was 739 € year−1. When the cost of the boiler purchase and its service and fuel purchase costs were taken into account, the 12-year operating cost for a briquette-fired boiler was found to be similar to the operation cost for a coal-fired boiler and higher by 21% compared to willow chips-fired boiler. The operation of a boiler fired with other fuels, like pellets, natural gas or heating oil during the same period was more expensive by 39%, 46% and 157%, respectively. • Wood briquette can be successfully used in automatic boilers for as long as 12 years. • The average consumption of briquettes for thermal energy generation was 7 Mg year−1. • Average heat energy consumption per 1 m2 of the house area was 0.45 GJ. • 12 year operating cost for a briquette boiler was similar to the cost for a coal. • The operation cost for a pellets, gas and oil boiler was expensive by 39, 46, 157%. [ABSTRACT FROM AUTHOR]

This paper aims at exploring a cleaner way of waste wood biomass grate-firing with a focus on NO X emission. The objective is to evaluate the potential of biomass co-combustion with methane for NO X abatement. NO X model involving three major gaseous N-species: NO, NH 3 and HCN is incorporated into the dynamic fuel bed model, in which the dependency of species release on the local oxygen is accounted for. Coupling with freeboard simulation, the NO X emission from a real scale grate boiler is predicted with good accuracy and details. Waste wood and methane co-combustion with fuel-staging is investigated. The methane co-combustion ratio is on an energy basis, and three values are chosen, 10%, 20%, and 30%. In the fuel-staging setup, it is found that a higher co-combustion fraction produces a better NO X reduction effect. This reduction is a result of less nitrogen input and NO reburning from hydrocarbon and other N-species. Moreover, while cutting down the total excess air, the reduction effect is enhanced from lower stoichiometry but accompanied by a diminished dilution for the NO X emission at stack. The results show that the reduction efficiency can achieve up to 45.3%. • Biomass co-combustion with methane effectively reduce NO X emission. • Co-combustion with cleaner fuel reduce toxic gas emission from input. • Both CH 4 –NO and HCN–NO reburning take effect during staged combustion. • Higher CH 4 injection has higher reduction efficiency with fuel staging. • The CH 4 co-combustion also generate efficiency benefit during co-combustion. [ABSTRACT FROM AUTHOR]