Conventional Combustion Systems Research Articles

Adaptive PMSM Control of Ship Electric Propulsion with Energy-Saving Features

Electric ship propulsion is considered one of the most promising alternatives to conventional combustion systems. Its goal is to reduce the carbon footprint and increase a ship’s maneuverability, operational safety, and reliability. The high requirements for ship propulsion make permanent magnet synchronous motors (PMSMs) an attractive solution due to their characteristics. This paper discusses the control problem of a PMSM based on the input–output feedback linearization method combined with the optimal and adaptive control techniques. The method presented here integrates the parameter tuning process with the optimal design of the baseline controller. Since the load disturbances are treated as an additional unknown parameter, there is no need to introduce an integral action to deal with the resulting steady-state error. An important feature of the designed controller is the so-called energetic optimization of the system; i.e., in addition to the aforementioned adaptive and optimal controller, it has a feature of ensuring zero reactive power consumed by the system. The performed simulations of the machine speed stabilization process confirmed the high efficiency of the proposed controller despite the assumed uncertainty of the system parameters and environmental (load) disturbances. Besides achieving high-quality control, an essential feature of this approach is the elimination of the tuning problem.

Research on low‐carbon system of biomass combustion and solar‐energy power generation based on MP‐PIC simulation

AbstractTo vigorously reduce CO2 emission in the energy sector is an inevitable choice to achieve world's carbon emission reduction and to accelerate the construction of a modern energy system. The development of CO2 capture, utilization, and storage technology (CCUS) is of great significance for promoting low carbon utilization of traditional energy and realizing the low carbon transformation of coal power industry. The joint development of biomass combustion integrated with new energy technology and consideration of fuel conversion CO2 capture from the source is a technical solution with high efficiency and low energy consumption in coordination, which will bring new development opportunities for conventional thermal power industry. In this study, a low carbon system of collaborative renewable energy CO2 source capture is constructed. Numerical simulation method of multiphase flow coupled with thermal mass transfer and chemical reaction of the combustion mathematical model is employed to study the combustion characteristics in the biomass combustion system. The combustion efficiency, carbon conversion, and pollutant emissions are calculated compared with the conventional coal combustion system. Hydrogen production and CO2 emissions are analyzed based on life cycle assessment method. The energy integration full‐chain system of geological storage and CCUS is optimized, which is committed to achieving nearly zero carbon emission in the thermal power industry, contributing to the global low CO2 emission work.

Toward Zero Carbon Emissions: Investigating the Combustion Performance of Shaped Microcombustors Using H2/Air and NH3/Air Mixtures

The research effort in the microcombustor field has recently increased due to the demand for high-performance systems in microelectromechanical and micro power generation devices. To address rising concerns about pollutants from fossil sources, zero-carbon fuels such as hydrogen (H2) and ammonia (NH3) have been considered as an alternative in microcombustion processes. In a microcombustor, the surface area-to-volume ratio is much higher compared to conventional combustion systems, resulting in faster heat transfer rates and more intense combustion reactions. However, achieving efficient mixing of fuel and an oxidizer in a microcombustor can be challenging due to its small size, particularly for highly reactive fuels like H2. For NH3, challenges in microcombustion involve a low reactive, high ignition temperature (923 K vs. 793 K of H2) and high concentration of NOx combustion products. Therefore, studying the performance of these fuels in microcombustors is important for developing clean energy technologies. In this paper, to explore features of non-premixed NH3/air and H2/air combustion in micro-scale combustors, an Ansys Fluent numerical investigation was conducted on a Y-shaped microcombustor. Results show that for combustion with H2, stationary flames can be achieved even at lower equivalence ratios. Additionally, the pollutants generated from H2 in the flame are generally twice those of NH3. The overall efficiency of the microcombustor is two times greater for NH3 conditions than for H2 conditions.

Experimental investigation of the co-combustion of LPG-hydrogen blends on LPG-fueled systems

The need for sustainable and less pollutant heating solutions has started an energy transition process. Some of the short-term alternatives proposed are based on the use of hydrocarbon-hydrogen blends in conventional combustion systems. In this work, LPG-H2 blends are studied in (a) a gas heater, (b) a water heater and (c) a porous media burner. Thermal and emission behavior, as well as thermal efficiency, are studied for different fractions of H2 in the fuel blend. Stable combustion was sustained for H2 volume fractions up to (a) 44%, (b) 68% and (c) 58%, for the above-mentioned appliances, respectively. Both gas and water heaters showed an overall reduction in thermal efficiency and temperatures as H2 presence was increased. On the other hand, higher temperatures, and thermal efficiencies, along with a 30% reduction in CO emissions were registered for the porous media burner for large H2 fractions in the fuel blend. In conclusion, the technical feasibility of adding H2 to the LPG feed lines of conventional combustion systems was demonstrated, through the stable operation of the 3 appliances studied.

CLIMATE AND ENVIRONMENTAL BACKGROUNDS OF FUEL UTILIZATION, INFLUENCING UPON ALTERATION THE EUROPEAN AND UKRAINIAN TRENDS OF GAS SUPPLY P.1 PRESENT REQUIREMENTS TO SELECTION THE GAS FUELS. THERMODYNAMIC EVALUATION THE PRINCIPAL CHARACTERISTICS OF GAS FUEL

The work examines the starting points on the formation of fuel markets in Europe within the framework of the concept of sustainable development of the countries’ economics, taking into account the main limitations, primarily the climatic and environmental consequences of fuels combustion. This approach has led in the past years to simultaneous increase in absolute volumes’ consumption of mineral (organic, carbon-rich) fuel’s flow rate and to reduction of their shares in the overall fuel balance. The relevant changes had occurred because of simultaneous production and consumption the alternative fuels, including renewable gas and energy sources. New schemes, methods and ways of fuel supply have been analyzed, including maritime transportation of liquefied fuels (liquefied natural gas LNG, liquid hydrocarbons LPG, ammonia NH3) along with creation of a modern tanker fleet with floating and land-based regasification and gas storage (FSRU) systems; systems of interconnecting the pipelines for fuel supply, including hydrogen-enriched natural gas (HENG). According to the cultivated opinion, the global warming is considered as a consequence of the carbonization of environment due to emission of C-rich combustion products (CO2) into the atmosphere. The specified contribution of CO2 to atmospheric pollution is caused by the insufficient efficiency of fuel use, for example, in heating furnaces (up to 40 % of the total amount of fuel consumed in the industry is burned in furnaces). If the emissions value of a conventional natural gas combustion systems in furnaces meets the level of emissions up to 0.45 kg СО2/kW.h, then in the case of equipping the furnace with an efficient waste gas heat recovery system, the emissions are reducing to 0.2–0.25 kg СО2/kW.h, (Wunning J.). The determinant role of the efficiency of fuel use ηf has been correlated with the scale of atmospheric pollution with greenhouse gases (CO2) emission by means of thermodynamic analysis of energy efficiency. The efficiency of fuel utilization: by enthalpy ηH and by exergy ηeff — has been computed for the cases of burning the widespread fuels and the comparative analysis has been performed. The calculations of thermal energy characteristics of the fuels have been carried out by using the original author’s methodology based upon assumption of equilibrium thermodynamics for the cases of using the widespread gas fuels within the temperature range T from the standard T0 to the theoretical combustion temperature TT. In accordance with original author’s method the most important heat engineering characteristics of the fuels have been studied by means of approaches of equilibrium thermodynamics. Higher and lower combustion heat, higher and lower Wobbe numbers, theoretical (adiabatic) combustion temperature of the widespread fuels have been determined. An influence of hydrogen content in CH4/H2 gas fuel mixtures on the mentioned properties has been determined. From the list of firing engineering characteristics, the formation of the methane number MN for different organic and alternative fuels have been considered. The accumulated numerical values of MN for the widespread types of fuels have been stated and compared. Bibl. 38, Fig. 4, Tab. 1.

Additive manufacturing new piston design and injection strategies for highly efficient and ultra-low emissions combustion in view of 2030 targets

Internal combustion engines have been the most effective solution as the main mover for mobility. Despite the recent European regulations targeting zero tailpipe CO2 emissions for new passenger cars and light vans from 2035 onwards, the upcoming emission regulations still require further technology and fuel developments in the transport sectors. In recent years, studies on internal combustion engines have been increasingly shifting from performance and refinement through advanced fuel injection and air charging technologies to ultra-low emissions and efficiency. Particular attention has also been paid to carbon–neutral fuels. The problem merits further investigation since all are key factors for the powertrain competitiveness in the electrified automotive future, as the pollutants and the CO2 emissions will soon approach the Euro 7 regulation and the Fit to 55 standards, respectively. To this aim, the combustion system design is a crucial part of the internal combustion engine development in the view of exploiting renewable fuel characteristics. This study seeks to assess the effectiveness of a steel piston, realized through a specific design for additive manufacturing technologies, enabling an innovative bowl geometry. It features a highly re-entrant sharp-step and radial lips bowl profile enabling spray separation and radial mixing zone concept. A single-cylinder compression ignition engine has been employed to demonstrate the effectiveness of the innovative bowl shape to meet the challenging future ultra-low emission targets. The results confirm the additive manufacturing technology as a possible solution for innovative highly-stressed steel piston designs. The new bowl shape design, combined with optimised spray targeting and injection strategies, allows outstanding soot reductions, up to 80%, and ultra-low NOx emission levels compared to the conventional combustion system. Gains in fuel economy are also observed. Further emissions advantages are expected with renewable fuel applications.

Combustion behavior study and flame zone analysis of biogas-fueled gas turbine combustor under O2/CO2 and O2/H2O oxidizing modes

Environmental problems resulting from the increment of greenhouse gases have raised the tendency toward using renewable energy sources alongside carbon-capturing technology via oxyfuel combustion. In this regard, numerical simulation on the feasibility of using renewable biogas in the gas turbine combustor under two combustion modes, namely, O2/CO2 and O2/H2O, at high operating pressure is investigated in the current research. Considering that conventional air-based combustion systems are not suitable for oxyfuel combustion regimes, the modification of the gas turbine combustor will be addressed to provide the necessary conditions for proper operation at higher power densities on an industrial scale. In this study, the focus is on investigating the influences of the primary diluent mass flow rate ratio (PDR) and the O2 content in the oxidizer composition on combustion and thermal behaviors of biogas flame such as distribution of reaction zone and temperature, combustion species, pattern factor, combustion efficiency, CO pollutant emission, and as well as flame stability in different combustion modes. The results indicated that the PDR parameter plays an essential role in the combustion stability within the gas turbine combustor due to its direct exposure to the vortices created in the recirculation zone. Moreover, combustion instabilities were observed for biogas flame at PDR = 15% in both combustion modes and in O2/H2O case at PDR < 25%. It was also found that CO emissions decrease significantly with increasing PDR, so in higher PDR values, CO pollutant levels were observed at 39 ppm and 21 ppm in O2/CO2 and O2/H2O cases, respectively.

Sustainable Combustion Technologies Need Acoustics Research

This paper outlines the challenges of developing hydrogen-fueled combustion systems, which are safe from combustion instabilities. Combustion instabilities can occur in any configuration where a continuously burning flame is housed in an acoustic resonator, such as gas turbine engines, boilers and furnaces. They manifest themselves by large-amplitude oscillations of one or more resonator modes and can cause major damage to the combustion system. Their underlying cause is the following feedback loop: the flow carrying the combustible mixture is perturbed → the flame becomes unsteady and its heat release fluctuates → the fluctuating heat release generates sound → the sound perturbs the flow of the mixture, and the feedback cycle is closed. Various strategies exist to prevent instabilities in conventional combustion systems, which burn hydrocarbon fuels. However, if hydrogen or a hydrogen-blend is used as fuel, the flame's dynamic behaviour changes, and as a consequence, combustion instabilities occur under new and unexpected conditions. In order to give some explicit physical insight, a generic combustion system will be presented and described by an analytical model. Predictions will be made about the impact of hydrogen fuel and other parameters.

Lean Methane Mixtures in Turbulent Jet Ignition Combustion System

The development of modern vehicle drives is aimed at reducing fuel consumption (i.e., crude oil) and minimizing the exhaust emission of toxic components. One such development is the implementation of a two-stage combustion system. Such a system initiates ignition in the prechamber, and then the burning mixture flows into the main chamber, where it ignites the lean mixture. The system allows the efficient combustion of lean mixtures, both liquid and gaseous fuels, in the cylinder. This article proposes a solution for internal combustion engines with a cylinder capacity of approx. 500 cm3. The tests were carried out on a single-cylinder engine powered by pure methane supplied through a double, parallel injection system. A wide range of charge ignitability requires the use of an active chamber containing an injector and a spark plug. The tests were carried out at n = 1500 rpm with three load values (indicated mean effective pressure, IMEP): 2, 4 and 6 bar. All of these tests were carried out at a constant value of the center of combustion (CoC), 8 deg CA. This approach resulted in the ignition timing being the control signal for the CoC. As a result of the conducted research, it was found that an increase in the load, which improved the inter-chamber flow, allowed for the combustion of leaner mixtures without increasing the coefficient of variation, CoV(IMEP). The tests achieved a lean mixture combustion with a value of λ = 1.7 and an acceptable level of non-uniformity of the engine operation, CoV(IMEP) &lt; 8%. The engine’s indicated efficiency when using a two-stage system reached a value of about 42% at λ = 1.5 (which is about 8 percentage points more than with a conventional combustion system at λ = 1.0).

Renewable Power and Heat for the Decarbonisation of Energy-Intensive Industries

The present review provides a catalogue of relevant renewable energy (RE) technologies currently available (regarding the 2030 scope) and to be available in the transition towards 2050 for the decarbonisation of Energy Intensive Industries (EIIs). RE solutions have been classified into technologies based on the use of renewable electricity and those used to produce heat for multiple industrial processes. Electrification will be key thanks to the gradual decrease in renewable power prices and the conversion of natural-gas-dependent processes. Industrial processes that are not eligible for electrification will still need a form of renewable heat. Among them, the following have been identified: concentrating solar power, heat pumps, and geothermal energy. These can supply a broad range of needed temperatures. Biomass will be a key element not only in the decarbonisation of conventional combustion systems but also as a biofuel feedstock. Biomethane and green hydrogen are considered essential. Biomethane can allow a straightforward transition from fossil-based natural gas to renewable gas. Green hydrogen production technologies will be required to increase their maturity and availability in Europe (EU). EIIs’ decarbonisation will occur through the progressive use of an energy mix that allows EU industrial sectors to remain competitive on a global scale. Each industrial sector will require specific renewable energy solutions, especially the top greenhouse gas-emitting industries. This analysis has also been conceived as a starting point for discussions with potential decision makers to facilitate a more rapid transition of EIIs to full decarbonisation.

Experimental study of flame zones variations of biogas enriched with hydrogen

Enriching biogas with hydrogen could enable conventional natural gas systems to be used for clean energy. This technique has generally been evaluated using laboratory devices, so this study addresses a conventional combustion system, consisting of a 100 kW burner fed with biogas-hydrogen mixtures instead of natural gas. Flame behavior and ignition behavior were investigated. The flame structure was analyzed by infrared thermography. The tests were performed with three different mixtures of CH4–CO2 recreating an energetically rich biogas, 30% CO2 (BG70), standard biogas 40% CO2 (BG60) and poor biogas 50% CO2 (BG60). Then, each biogas type was enriched with hydrogen up to 20%. Major improvements were obtained between 5% and 10% hydrogen composition since the flame stability increases considerably. Flame structure closest to natural gas flame was achieved for BG60 and BG70 at 10% H2. However, the flame temperature remained lower than that of natural gas in all cases.

The role of H2O in NO formation and reduction during oxy-steam combustion of bituminous coal char

To improve the CO2 capture efficiency and reduce energy penalties in conventional oxy-fuel combustion systems, one possibility is to eliminate the use of recycled flue gas, by using steam and O2. This is known as oxy-steam combustion. However, the role of H2O in NO formation and reduction under oxy-steam combustion is not yet clear. Here, NO emissions during oxy-steam and air combustion of coal char were compared using both experiments and theoretical calculations, with an emphasis of the role of H2O and its resulting radicals in NO formation and reduction reactions. High concentration of H2O promotes both OH radicals and hydroxyl groups formation during oxy-steam combustion, which in turn effects NO formation and reduction reactions and eventually NO emissions. Specifically, NO formation under air combustion is largely determined by HCN conversion to NCO and then NO, whereas under oxy-steam combustion, high concentrations of OH radicals cause HCN to form NH2 and eventually NO as the dominant route. However, the conversion of HCN to NH2 and then NO is faster, and hence these OH radicals accelerate HCN oxidation to NO under oxy-steam combustion. Given that OH radicals and hydroxyl groups have little influence on NO reduction to N2, there is more NO production in oxy-steam combustion that air combustion.

Thermal and flow characteristics of liquid flow in a 3D-printed micro-reactor: A numerical and experimental study

• Stereo lithography was utilised to construct pin–fin photo-thermal micro-reactors. • 3D printing was successfully utilised to print micro-pin fins inside microchannels. • Thermal and fluid characteristics of constructed micro-reaactors were assessed. • Validated CFD model was used to evaluate velocity and pressure profiles. • Size of pin-fins in micro-reactor was optimised with response surface modelling. In this article, we report on a unique design and build technique based on stereolithographic 3D printing technology (SLA) for constructing ultraviolet cured resin-made micro-reactors. The main objective of this study is gaining insight into the thermal performance of micro-reactors for optofluidic applications. Several micro-reactors equipped with pin fins were manufactured. A high-fidelity test-rig was developed and used to collect data from water flowing in the micro-reactors as they are exposed to various heat flux loading. The measured data was also used for validating the numerical (CFD) models. The CFD models provided in-depth spatial data on the pressure and temperature profiles in the microchannel, which could not be easily measured. The results showed that conventional empirical correlations failed to accurately predict the pressure drop of the system in the microfluidics regime (Re < 190), although are reasonably accurate in the conventional fluid regime (Re > 190). For both regimes, however, CFD results were sufficiently accurate in predicting the temperature and pressure differences across the micro-reactor. It was also identified that pin fins arrangements offer a great design benefit in enhancing heat transfer coefficient in micro-reactors, achieving values up to ∼2300 W/m 2 .K compared to a plain micro-reactor at ∼1875 W/m 2 .K (or 300 W/m 2 .K for conventional combustion systems). A multi-objective optimisation on the geometrical specifications of various pin fins showed that the micro-reactor with pin fins of 250 µm in diameter and 100 µm in height, yielded the best thermo-hydraulic performance of highest thermal transfer coefficient (2100 W/m 2 .K) and the lowest pressure- drop (∼0.1 kPa) across a wide range of heat flux loadings. The outcome of this study has created a significant knowledge and understanding of the flow behaviour in polymer-based micro-channels. It also established a methodology for designing and optimising the thermal–hydraulic performance of optofluidic micro-reactors, with potential loading of nano-photocatalyst mediated in pin fins sites. New correlations for predicting the pressure drop and temperature difference across polymer-based micro-reactors are also developed.

Hybrid Electric Vehicles: A Review of Existing Configurations and Thermodynamic Cycles

The mobility industry has experienced a fast evolution towards electric-based transport in recent years. Recently, hybrid electric vehicles, which combine electric and conventional combustion systems, have become the most popular alternative by far. This is due to longer autonomy and more extended refueling networks in comparison with the recharging points system, which is still quite limited in some countries. This paper aims to conduct a literature review on thermodynamic models of heat engines used in hybrid electric vehicles and their respective configurations for series, parallel and mixed powertrain. It will discuss the most important models of thermal energy in combustion engines such as the Otto, Atkinson and Miller cycles which are widely used in commercial hybrid electric vehicle models. In short, this work aims at serving as an illustrative but descriptive document, which may be valuable for multiple research and academic purposes.

Numerical and experimental methods in development of the novel biomass combustion system concept for wood and agro pellets

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/mn3 at 10% of O2 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.

Solid particulate mass and number from ducted fuel injection in an optically accessible diesel engine in skip-fired operation

Ducted fuel injection (DFI) is a novel combustion strategy that has been shown to significantly attenuate soot formation in diesel engines. While previous studies have used optical diagnostics and optical filter smoke number methods to show that DFI reduces in-cylinder soot formation and engine-out soot emissions, respectively, this is the first study to measure solid particle number (PN) emissions in addition to particle mass (PM). Furthermore, this study quantitatively evaluates the use of transient particle instruments for measuring particles from skip-fired operation in an optical single cylinder research engine (SCRE). Engine-out PN was measured using an engine exhaust particle sizer following a catalytic stripper, and PM was measured using a photoacoustic analyzer. The study improves on earlier preliminary emissions studies by clearly showing that DFI reduces overall PM by 76%–79% and PN for particles larger than 23 nm by 77% relative to conventional diesel combustion at a 1200-rpm, 13.3-bar gross indicated mean effective pressure operating condition. The degree of engine-out PM reduction with DFI was similar across both particulate measurement instruments used in the work. Through the use of bimodal distribution fitting, DFI was also shown to reduce the geometric mean diameter of accumulation mode particles by 26%, similar to the effects of increased injection pressure in conventional diesel combustion systems. This work clearly shows the significant solid particulate matter reductions enabled by DFI while also demonstrating that engine-out PN can be accurately measured from an optical SCRE operating in a skip-fired mode. Based on these results, it is believed that DFI has the potential to enable fuel savings when implemented in multi-cylinder engines, both by lowering the required frequency of active diesel particulate filter regeneration, and by reducing the backpressure imposed by exhaust filtration systems.

Thermochemical utilization of low rank coal and flotation concentrate

Flotation concentrates are waste material from coal mine operation. The process of steam gasification seems to be an attractive option for their economic utilization and an alternative to their potential combustion in boilers. The gasification process is characterized by both higher efficiency and lower emission of pollution than conventional combustion systems. In this paper the results of the steam gasification of low rank coal and flotation concentrate into hydrogen-rich gas at the temperature of 800 °C are presented. The reactivity for 50% carbon conversion as well as the maximum reactivity in this process were calculated for the samples studied.

1D numerical study on hydrogen injection enabling ultra-lean combustion in a small gasoline Spark Ignition engine

This paper deals with the effects of hydrogen port injection on combustion evolution, efficiency and exhaust emissions of a small turbocharged gasoline Spark-Ignition engine through a 1D numerical code. First, the experiments on the base engine architecture are performed at different speeds and at low/medium loads. The experimental findings are used to validate a 1D model of the whole engine, developed within a commercial code. 1D model is also refined with “user-defined” sub-models for an accurate description of the in-cylinder phenomena, namely turbulence, combustion, heat transfer, and emissions. In a second step, 1D model is virtually modified through the installation of an hydrogen injector in each intake runner, while the combustion sub-model also accounts for the impact of hydrogen addition on the laminar flame speed through a dedicated correlation. 1D simulations are performed at low/medium loads and fixed speed of 2250 rpm with 5% of hydrogen by volume in the intake air. Numerical investigations show that hydrogen addition to gasoline/air mixtures allows relevant efficiency benefits (up to a maximum percent gain of 19%), while the NO emissions are almost eliminated. Consequently, hydrogen-boosted combustion represents a potential solution to achieve very high efficiency and reduced pollutant emissions of gasoline spark ignition engines equipped with a conventional combustion system.

Effects of chemical reaction mechanism and NOx formation pathways on an inter-turbine burner

ABSTRACTOne of the main challenges of future aircraft engines is to achieve low pollutant emissions while maintaining high combustion efficiencies and operability. The Flameless Combustion (FC) regime is pointed as one of the promising solutions due to its well-distributed reaction zones that yield low NOx emissions and oscillations. A dual-combustor configuration potentially facilitates the attainment of FC in the Inter-Turbine Burner (ITB). The development of such burner is dependent on knowledge regarding NOx formation and the parameters affecting it. It is known from the literature that the NOx formation mechanisms are different in FC. Therefore, in an attempt to clarify some of the mechanisms involved in NOx formation at relevant conditions, a chemical reactor network model developed to represent the ITB is explored. The role of prompt NOx was previously shown to be dominant at relatively low inlet temperatures and atmospheric pressure. In order to check these findings, five chemical reaction mechanisms were employed. All of them overpredicted NOx emissions and the overprediction is likely to be caused by the prompt NOx subset implemented in these mechanisms. Higher reactants temperatures and operational pressures were also investigated. Overall NOx emissions increased with temperature and the NOx peak moved to lower equivalence ratios. Operational pressure changed the emissions trend with global equivalence ratio. Leaner conditions had behaviour similar to that of conventional combustors (increase in NOx), while NOx dropped with further increase in equivalence ratio due to suppression of the prompt NOx production, as well as an increase in NO reburning. These trends highlight the differences between the emission behaviour of the ITB with those of a conventional combustion system.

Thermochemical utilization of low rank coal and flotation concentrate

Abstract Flotation concentrates are waste material from coal mine operation. The process of steam gasification seems to be an attractive option for their economic utilization and an alternative to their potential combustion in boilers. The gasification process is characterized by both higher efficiency and lower emission of pollution than conventional combustion systems. In this paper the results of the steam gasification of low rank coal and flotation concentrate into hydrogen-rich gas at the temperature of 800 °C are presented. The reactivity for 50% carbon conversion as well as the maximum reactivity in this process were calculated for the samples studied.