Low Nitrogen Oxide Emissions Research Articles

Effects of internal/external EGR and combustion phase on gasoline compression ignition at low-load condition

Abstract A single-cylinder test engine model was built by GT-Power software, and the effects of internal exhaust gas recirculation (i-EGR), external EGR (e-EGR), i-EGR/e-EGR coupling and the crank angle degree at which 50% of total heat loss has taken place (CA50) on combustion and emission characteristics of gasoline compression ignition at low-load condition were analysed. The results show that the ignition delay period with e-EGR was extended slightly with the increased EGR ratio, while that with i-EGR strategy first shortened and then extended, and that the optimised indicated thermal efficiency could be achieved using a small amount of i-EGR. With the same EGR ratio, nitrogen oxide (NO X ) emission is more likely to be suppressed by i-EGR, while soot emission was more deteriorated, and the superior trade-off relationship between carbon monoxide (CO)/hydrocarbon (HC) emissions and NO X emission was attained by the combination of lower i-EGR ratios and CA50 closed to top dead centre. When using i-EGR/e-EGR coupling with total EGR ratio being fixed, the indicated thermal efficiency was decreased by increasing i-EGR ratio, while the lower NO X , CO and HC emissions could be realised, but only with the consequence that soot emission increased.

Performance and ecological parameters of a diesel engine fueled with diesel and plastic pyrolyzed oil (PPO) at variable working parameters

Plastics are one of the major pollutants to the environment. An investigation is carried out in converting low density polyethylene (LDPE) to oil by pyrolysis method with the aid of catalyst for the use in internal combustion engines. Experiments were conducted at different speeds (1200, 1500 and 1800 rpm) and variable loads (low, medium and full) with constant compression ratio engine to evaluate the performance and ecological parameters. Plastic pyrolyzed oil (PPO) is blended with diesel fuel in 20:80 volume proportion to get D80PO20 blended mixture which is employed in engine in order to assess its characteristics. Encouraging outcomes have been obtained as cylinder pressure in combustion is of same order as that of diesel fueled engine. The results showed that increasing engine speeds resulted in higher cylinder pressure and brake thermal efficiency. Also, high nitrogen oxide (NOX) and low brake specific energy consumption (BSFC) has been identified. Lower smoke (BSN) and NOX emissions are noticed from engine tail pipe with D80PO20 blended mixture.

Numerical Study to Achieve Low Fuel Consumption and Nitrogen Oxides Emissions in a Split-Cycle Engine Adapted from the Conventional Architecture

Numerical Study to Achieve Low Fuel Consumption and Nitrogen Oxides Emissions in a Split-Cycle Engine Adapted from the Conventional Architecture

The effects of natural gas composition on conventional dual-fuel and reactivity-controlled compression ignition combustion in a heavy-duty diesel engine

The use of natural gas (NG) in dual-fuel heavy-duty engines has the potential to reduce pollutant and greenhouse gas (GHG) emissions from the transport sector when compared to the conventional diesel engines. However, NG composition and methane slip are of interest because both can adversely affect the benefits of NG as an alternative fuel, especially when considering GHG emissions. Therefore, this study experimentally investigated the effects of NG fuel properties on the performance and emissions of both conventional dual-fuel and reactivity-controlled compression ignition (RCCI) engine operations. Three different gas mixtures were selected to simulate typical NG compositions available in the world market, with methane numbers (MN) of 80.9, 87.6 and 94.1. These fuels were tested in a single-cylinder compression ignition engine operating at 0.6, 1.2 and 1.8 MPa net indicated mean effective pressure (IMEP). A high-pressure common rail system allowed for the use of various diesel injection strategies while a variable valve actuation system enabled the effective compression ratio to be adjusted via late intake valve closing (LIVC). The RCCI combustion was found to be more sensitive to changes in MN than the conventional NG-diesel dual-fuel operation. The gas mixture with the lowest MN reduced both total unburned hydrocarbons emissions and methane slip at the expense of higher nitrogen oxides (NOx) emissions. The effects of MN on the net indicated efficiency were more significant at 0.6 MPa IMEP, yielding differences of up to 4.9% between the RCCI operations with the lowest and highest MN fuels. Overall, this work revealed that the combination of the RCCI combustion and LIVC can achieve up to 80% lower methane slip and NOx emissions and relatively higher net indicated efficiency than the conventional dual-fuel regime, independent of the NG composition.

Feasibility study of the combustion strategy of n-butanol/diesel dual direct injection (DI2) in a compression-ignition engine

For n-butanol/diesel dual-fuel combustion, there are two different implementations, i.e., dual direct injection (DI2) strategy and reactivity controlled compression ignition (RCCI) strategy. The DI2 strategy is a novel combustion concept, which is expected to address the inefficient combustion and high pressure rise rate dilemmas raised by RCCI. In this work, the full-parameter optimizations of DI2 and RCCI were first performed at mid load, and the optimal cases were comprehensively compared. The potential benefits of DI2 over RCCI and its optimal operating parameters were determined. The results indicate that DI2 can achieve low nitrogen oxides (NOx) emissions below 0.00094 g/kWh and near-zero soot emissions while keeping high fuel economy near 167 g/kWh comparable to that of RCCI, but it usually yields higher NOx, soot, and carbon dioxide (CO2) emissions than RCCI. In the optimal DI2 cases, very advanced n-butanol injection timing (before −120°CA ATDC), high n-butanol energy fraction (around 0.94), and early diesel injection timing (near −50 °CA ATDC) are adopted. Meanwhile, the combination of a narrow n-butanol spray angle (30°<αbutanol < 50°) and a wide diesel spray angle (>65°) is preferred for DI2. Compared with RCCI, DI2 exhibits lower combustion losses, however, it suffers from higher exhaust and heat transfer losses. The higher intake temperature, exhaust gas recirculation (EGR) rate, and lower intake pressure are more beneficial for DI2. Moreover, it is suggested that DI2 is easier to achieve lower ringing intensity (RI), and the ignition timing and RI of DI2 are more sensitive to the n-butanol fraction than RCCI.

Model development and experimental validation of an exhaust brake supported dual loop exhaust gas recirculation on a medium duty Diesel engine

Due to the new European emission norms internal combustion engines have to comply stricter rules. The new norms contain new requirements that were not included in previous regulations for example the decreased temperature of the cold start or the real driving emission part. The emission cycles for passenger vehicles are completely news, the stricter emission norms for commercial vehicles will follow them within a few years. Despite the increasing spread of alternative transmission systems in road transport Diesel engines are going to be remain in commercial vehicles in the next decades due to their good torque and fuel consumption performance. The emission of Diesel engines can be kept low by several way: by the modification of combustion processes, or by exhaust gas after treatment. To comply future regulations both of them seems to be necessary. By exhaust gas recirculation systems alternative Diesel combustion processes can be realized which can provide lower nitrogen-oxide emission and in several operation points also lower fuel consumption. Exhaust gas recirculation systems also can support the thermal management of a Diesel engine. To utilize the advantages of the recirculated exhaust gases a complex system is necessary to get a freedom in control possibilities: duel loop exhaust gas recirculated systems supplemented with supporter valves on the intake or on the exhaust side. In this paper a pressure and mass flow rate based control oriented engine model will be presented which contains high and low pressure exhaust gas recirculation systems and both of them are supported by exhaust brakes. The model considers four balance volumes and it has five state variables. The model is validated by an engine dyno measurements on a medium duty Diesel engine.

Optimization of separated overfire air to reduce NOX emissions under combustion stability for the retrofit of a 500 MW tangentially pulverized coal boiler

Retrofitting of an aging 500 MW tangential coal-fired boiler with high pollutant emissions in South Korea was investigated to achieve low nitrogen oxide (NOX) emissions and high combustion efficiency. This study evaluated and analyzed the combustion and emission characteristics of five arrangements to optimize the position and direction of a separated overfire air (SOFA) installation using a computational fluid dynamics (CFD) simulation. The results show that the air injection of SOFA at the center of the boiler wall causes substantial obstruction of the rising airflow below, causing unstable combustion behavior in the boiler, and increasing the amount of unburned carbon (UBC). However, combining the wall injection with corner SOFA helps reduce the formation of NOX and has the effect of promoting the burnout of UBC. For the direction of the wall injection under combined conditions, a clockwise airflow helps to reduce the formation of NOX with increasing UBC. Otherwise, the counter-clockwise airflow weakens the flow rate of the ascending airflow, increasing the residence time of unburned particles, increasing the coal burnout rate, and increasing the furnace exit gas temperature (FEGT). Among the five SOFA arrangements studies, this study recommends Case 4, which has a clockwise wall SOFA (30%) with corner SOFA (70%). This case has the best performance in terms of combustibility, NOX emission, UBC, and FEGT. The proposed condition was verified through a field test, and the results indicate that NOX emissions decreased from 169 ppm to 57 ppm, the UBC content decreased from 3.64% to 0.7%, and the boiler efficiency increased by 2%.

Numerical variational study of the M-shaped boiler invert furnace

Nowadays the world and Russian energy sector seeks to reduce the use of coal for electricity production, however, in the future its significant part will remain in the fuel balance. Due to environmental and economic factors, coal generation has to use technologies to reduce polluting emissions and including also CO2 (HELE technologies) for maintain competitiveness. One of these technologies is the use of a coal for A-USC steam parameters steam turbine cycle. This paper describes the studies conducted to develop the optimal scheme for burning solid fuel in an A-USC M-shaped boiler invert furnace proposed by the Dept. of Thermal Power Plants of the National Research University “Moscow Power Engineering Institute”. Six schemes with a different arrangement of direct-flow burners and nozzles are considered. A test installation for isothermal physical modeling was made for scheme No.1. The results of physical modeling were compared with the results of the numerical simulation model of the test installation. Schemes No. 1-6 were investigated using numerical simulation in the ANSYS software package to identify the best conditions for the organization of staged fuel combustion at low emissions of nitrogen oxides. Scheme 6 is recognized as the most optimal and will be used to create an isothermal physical test installation and conduct numerical simulations of the combustion process for a full-scale furnace model.

Summertime O3 and related health risks in the north China plain: A modeling study using two anthropogenic emission inventories

Ground-level ozone (O3), which is formed by photochemical reactions of nitrogen oxides (NOx) and volatile organic compounds (VOCs), exert adverse effects on human health. In China, the mechanism and influencing factors of high O3 levels are not well understood in China despite the frequent occurrence of extreme episodes in recent years with decreasing concentrations of particulate matter. In this study, the O3 concentrations in summer 2017 in the North China Plain (NCP) are simulated using the Community Multiscale Air Quality (CMAQ) model with anthropogenic emissions from the Multi-resolution Emission Inventory for China (MEIC) and improved Emission Database for Global Atmospheric Research (EDGAR+). Moreover, the performances of the model with the two emission inventories are validated and compared. The simulation using EDGAR+ is found to be highly accurate in predicting O3 in the NCP, whereas that using MEIC has better performance in matching peak concentrations in extreme episodes. Weather conditions, such as high temperature, low relative humidity, and stable conditions, are associated with high O3 concentrations in both inventories. Compared with MEIC, lower NOx emissions (by 200 tons/grid/month) from EDGAR+ induce higher O3 concentrations when VOCs emissions are barely changed (by less than 5 tons/grid/month). In the EDGAR+ scenario, a total of 42,000 and 69,000 premature mortalities are estimated to be caused by O3-related respiratory and cardiovascular diseases, respectively. These values are slightly lower than those in the MEIC scenario, i.e., 50,000 and 80,000, respectively. Megacities, such as Beijing and Tianjin, are classified as high-risk areas, with more than 15,000 mortalities.

Numerical simulation on lean-burn characteristics of a naturally aspirated opposed rotary piston engine fuelled with hydrogen at wide open throttle conditions

Opposed rotary piston engines are characterized by high power density, which makes them as an ideal power source for hybrid vehicles and range extended electric vehicles. Hydrogen applications can fully exhibit the merits of opposed rotary piston engines, and achieve zero carbon dioxide emissions; however, the applications seriously worsen the nitrogen oxides emissions. In this investigation, lean-burn was adopted to achieve low nitrogen oxides emissions using a three dimensional numerical simulation approach. The results indicated that engine speed of 3000 r/min presented the highest in-cylinder pressure during combustion among the given scenarios, and the pressure over 3000 r/min depended more on the equivalence ratio than that of 1000 r/min and 2000 r/min. Heat release rates were very sensitive to low equivalence ratio. Combustion duration over the equivalence ratio of 0.8 was the shortest among 1000 r/min cases; however, it decreased with equivalence ratio for 2000 r/min and 3000 r/min. Heat loss rates through cylinder walls increased significantly with engine speed, meanwhile they were more dependent on the equivalence ratio over higher engine speed. Maximum nitrogen monoxide formation rates over 3000 r/min occurred slightly earlier than those of 1000 r/min and 2000 r/min. Equivalence ratio of 0.8 showed the highest indicated thermal efficiency over corresponding engine speed, and nitrogen dioxide emission factors were quite low over the equivalence ratio of 0.7 for the given engine speed.

Dynamic modeling and offset-free predictive control of LNG tank

Due to tightened regulations on sulfur oxide (SOx) and nitrogen oxide (NOx) emissions, especially, in the ocean industry, liquefied natural gas (LNG) is becoming more important as an eco-friendly fuel source because of its extremely low SOx and NOx emissions. However, since LNG is usually stored at below its boiling temperature (-160°C) and slightly above the atmospheric pressure, the invasion of natural heat causing evaporation of LNG is inevitable even with proper insulation. This evaporated LNG called boil-off gas (BOG) accumulates inside the tank, and without proper venting, the pressure inside the tank will build up and eventually reach the maximum allowable working pressure (MAWP) of the storage tank. The violation of this threshold will lead to serious consequences. Therefore, safe control of storage tank pressure is critical to its safe operation. In this paper, we propose to use a model predictive control (MPC) system to regulate the LNG tank pressure. Firstly, a dynamic model of the LNG storage tank is developed using the film evaporation theory. Secondly, a reduced-order model is developed using the N4SID algorithm. Finally, the offset-free MPC system scheme is applied to control the tank pressure. For demonstrating the performance of the offset-free MPC system in unnatural circumstances, a fire around the tank is applied. The results show that the offset-free MPC system is able to regulate the pressure even when a fire accident occurs despite the plant-model mismatch in such conditions.

Evaluation of pure rapeseed oil as a renewable fuel for agricultural machinery based on emission characteristics and long-term operation behaviour of a fleet of 18 tractors

The usage of locally produced pure rapeseed oil fuel (R100) according to fuel standard DIN 51605 in agricultural machinery can contribute to protecting the climate, water, and soil. Besides economic aspects, uncertainties concerning the long-term operation reliability and limited exhaust emissions of R100-operated agricultural machinery are hindering market entry. Thus, the aim of this research is to evaluate field experiences, such as downtimes and repairs, engine oil quality, and cold start behaviour, over a total period of more than 50,000 operation hours with 18 tractors. The tested tractors range from European Union exhaust gas stages I to IV and were configured for the use of R100. Additionally, performance, nitrogen oxides, and particulate matter were measured on a tractor test stand. The tractors demonstrated their full functionality under usual Bavarian farm conditions in daily use. Within the tractor fleet, no serious engine damage was observed, while minor malfunctions and necessary repairs occurred just occasionally. The operational reliability of the tested rapeseed-oil-fuelled tractors seemed to be comparable to that of diesel-fuelled tractors. The results of recurrent power and fuel consumption measurements gave no indication of engine deterioration. Furthermore, measurements proved that differences in exhaust gas emissions between R100 and diesel operation were marginal. Tractor models with exhaust gas after treatment systems were characterized by low emissions of nitrogen oxides and particulate matter in particular. With the 18 tractors running on R100, about 220 tonnes of CO2eq per year were saved on average from 2015 to 2017. It can be concluded that the usage of pure rapeseed oil fuel (R100) in compatible agricultural machinery is an implementable alternative to diesel fuel and can make an important contribution to reducing greenhouse gas emissions in agriculture. Nevertheless, there are some challenges to solve, particularly for modern agricultural machines with engines with exhaust gas aftertreatment systems.

Characteristics of the real-driving emissions from gasoline passenger vehicles in the Kuala Lumpur urban environment

Emission factors (EFs) are empirical functions that envisage the amount of an emitted pollutant based on travel activity and vehicle characteristics. This paper aims to estimate on-road gaseous emission factors of gasoline passenger vehicles under urban Malaysian road traffic conditions. Eleven vehicles were tested and the carbon monoxide (CO), carbon dioxide (CO2) and nitrogen oxides (NOx) emission results were analyzed according to driving conditions. The effects of inter-vehicle variability in terms of accumulated mileage on emission factors were explored using regression analysis. The links of real driving condition on exhaust emissions were examined using hierarchical cluster analysis. The emission factors of CO, CO2 and NOx were calculated using a fuel-based approach. The 95% confidence intervals obtained for the population mean of emission factors were CO: 0.76 ± 0.15 g/km, CO2: 236.02 ± 14.98 g/km, NOx: 0.23 ± 0.03 g/km. Vehicle age as echoed by accumulated mileage was responsible for the increase in the average emission factors of CO and NOx. The results of the cluster analysis formed four meaningful clusters which described driving conditions and exhaust emissions. Higher observations were recorded for Cluster 1 (43.25%) indicating low vehicle speed and better fuel efficiency produced low NOx and CO emissions but high CO2 emissions. The measurements reported in this paper highlight the significance of this work in quantifying CO, CO2 and NOx emissions from gasoline passenger vehicles under real-world driving conditions of urban street in Malaysia where there is a paucity of EFs studies.

Why is the Indo-Gangetic Plain the region with the largest NH&amp;lt;sub&amp;gt;3&amp;lt;/sub&amp;gt; column in the globe during pre-monsoon and monsoon seasons?

Abstract. Satellite observations show a global maximum in ammonia (NH3) over the Indo-Gangetic Plain (IGP), with a peak from June to August. However, it has never been explained explicitly. In this study, we investigated the causes of high NH3 loading over the IGP during the pre-monsoon and monsoon seasons using WRF-Chem (Weather Research and Forecasting model coupled to chemistry). The IGP has relatively high NH3 emission fluxes (0.4 t km−2 month−1) due to intensive agricultural activities and high air temperature from June to August. Additionally, low sulfur dioxide (SO2) and nitrogen oxides (NOx) emissions and high air temperature limit the gas-to-particle conversion of NH3, particularly for ammonium nitrate formation. Moreover, the barrier effects of the Himalayas in combination with the surface convergence weaken the horizontal diffusion of NH3. The high NH3 loading over the IGP mainly results from the low gas-to-particle partitioning of NH3 caused by low SO2 and NOx emissions. It contrasts to those in the North China Plain, where high SO2 and NOx emissions promote the conversion of gaseous NH3 into particulate ammonium.

The impact of the metallic modifiers on the ecological and economic efficiency of the heavy fuel oils combustion process

The combustion of liquid fuels (mainly of heavy fuel oils) generates pollutants such as carbon monoxide (CO), nitrogen oxides (NOx), sulfur dioxide (SO2) and hydrocarbons (HC). Specific modifiers have been designed to reduce these environmental emissions by improving the combustion process. This research work presents the results of studies into the impact of a monometallic modifier comprising Fe salts, dimetallic modifier comprising Fe and Mg salts, and a trimetallic modifier comprising Fe, Mg and Ce salts, on the combustion of spent oils mixed with light fuel oil. The oil combustion tests were carried out in a 30 kW three-draft water boiler. The modifiers’ impact on the combustion of the oil mixture was studied at varying air-excess values. The modifier was injected into the oil stream flowing into the boiler, by means of a dedicated applicator. The results indicate that the trimetallic modifier results in lower CO and NOx emissions but higher SO2 emissions and higher boiler efficiencies than the dimetallic modifier. No catalytic activity was observed in the oil mixture combustion tests where the monometallic modifier was used. The benefits of using the modifier should be assessed on the basis of the cost of 1 Mg of fuel oil and the savings resulting from using the modifier and from the refurbishment. It was showed that depending on the capacity, savings due to the use of the modifier are in the range 2–4%, and those due to the system refurbishment are about 4–6%. For such savings, the return on the investment will occur after a period of time ranging from 3 years for large boiler plants to 5 years for smaller system capacities. All payback periods depend directly on the modifier system installation, on the modifier type, on the technical condition of the boiler plant and the costs of its refurbishment.

Experimental investigation on the characteristics and performance of homogeneous charge induced ignition(HCII) on a multi-cylinder heavy-duty engine

This paper is focused on the characteristics and performance of HCII in conditions close to practical engine operating. For this purpose, extensive experiments have been conducted on a modified six-cylinder heavy-duty diesel engine, with six-cylinder HCII, high pressure exhaust gas recirculation(EGR) loop and appropriate pressure rise rate. The experiments mainly include two aspects. Firstly, gasoline ratio(GR), EGR ratio and start of injection(SOI), are studied to summarize the combustion and emission characteristics of HCII. Secondly, European steady state cycle(ESC) test is conducted to evaluate HCII performance over the whole engine map.Results suggest that large GR is beneficial to effective thermal efficiency(ETE) or/and nitrogen oxide(NOx) and smoke emissions, however, it is limited by maximum pressure rise rate at low load and uncontrollable ignition time at high load. Similarly, the application of EGR can improve gasoline combustion and decrease NOx emission, while it cannot be too much because of decreased ETE at low load and uncontrollable ignition time at high load. Meanwhile, SOI can be advanced to 40 crank angle degree(CAD) before top dead center(BTDC) to achieve extremely low NOx and smoke emissions and relatively high ETE. However, this strategy can only be applied to B25 and C25 points. Finally, great success is achieved by HCII in ESC test. Just with diesel oxidation catalyst(DOC), the weighted specific emissions of NOx, particulate matter(PM), hydrocarbon(HC) and carbon monoxide(CO) can be 1.841 g/(kW·h), 0.024 g/(kW·h), 0.115 g/(kW·h) and 0.896 g/(kW·h) respectively.

Effect of balance valve on an asymmetric twin-scroll turbine for heavy-duty diesel engine

A conventional asymmetric twin-scroll turbine with wastegate is capable of effectively tackling down the contradiction between fuel economy degradation and low nitrogen oxide emissions. However, as the engine speed has been rising at middle- and high-speed ranges, the pressure of small scroll inlet will be increasingly higher as compared with the intake pressure, thereby worsening fuel economy. In this study, a novel turbocharging technology of asymmetric twin-scroll turbine with a balance valve was first analyzed to more effectively balance the engine fuel economy and emission. The experiments on turbine test rig and engine performance were performed to explore the effects of balance valve on turbine performance, asymmetric ratio, exhaust gas recirculation rate, as well as engine performance. As the balance valve open degree was elevated, the turbine flow parameter was being extended, while the turbine efficiency was enhanced. Moreover, a lower asymmetric ratio could lead to a broader flow parameter range between that of partial admission and equal admission, thereby resulting in a broader regulating range of exhaust gas recirculation rate. In contrast with the asymmetric twin-scroll turbine with wastegate, the turbine running efficiency of asymmetric twin-scroll turbine with balance valve was enhanced by nearly 2%–11% at middle and high engine speed ranges, while the fuel economy was improved by nearly 1.5%–8%.

Numerical simulation on optimization of structure and operating parameters of a novel lean coal decoupling burner

Abstract Due to its low volatile characteristics of lean coal, it is difficult to catch fire and burn out. Therefore, high temperature is needed to maintain combustion efficiency, while, this leads to high nitrogen oxide emission. For power plant boilers burning lean coal, stable combustion with lower nitrogen oxide emission is a challenging task. This study applied the 3D numerical simulation on the analysis of a novel de-coupling burner for low-volatile coal and its structure and operation parameters optimization. Results indicate that although it was more difficult for lean coal decoupling burner to ignite lean coal than high volatile coal, the burner formed a stepwise ignition trend, which promoted the rapid ignition of lean coal. Comparison of three central partition plate structure shows that in terms of characteristics of the flow field distribution, rich and lean separation and combustion, the structure with an inclination of 0 ° showed good performance, with its rich-lean air ratio being 0.85 and concentration ratio being 22.94, and there was an apparent decoupling combustion characteristic. Finally, the structure of the selected burner was optimized for its operational conditions. The optimal operating parameters was determined as the primary air velocity of 24.9 m/s and the mass flow rate of pulverized coal of 2.5 kg/s, in which the pyrolysis products were utilized as reductive agent more fully. Eventually, the nitrogen oxide was efficiently reduced to nitrogen, which emission concentration was 61.88% lower than that in the design condition.

Investigation of the interaction of turbulent jets in furnaces with direct-flow burners for high-power boilers

The aim of the study is to develop a highly efficient scheme of combustion of low-grade solid fuels with the realization of regulatory requirements for emissions of hazardous substances into the atmosphere. One of the directions of practical application of such a scheme is conversion of boilers with liquid slag removal to solid slag removal. Liquid slag removal boilers have a number of disadvantages that make their use in modern conditions impractical: reducing the reliability of the liquid slag at low loads and high emissions of NOx nitrogen oxides, which exceed the standard values 2-3 times. In light of amendments to the environmental legislation of the Russian Federation, changing the order and rates of payment for emissions of hazardous substances from 2020, thermal power plants will be forced to implement environmental measures to ensure normative values of specific emissions. The basic principles of effective solid fuel burning organization with the application of direct-flow burners have been formulated on the basis of the conducted research.

Investigation of the Combustion Process of Solid Fuel in Furnaces with Direct-Flow Burners

The optimization of the boiler furnace’s aerodynamics is considered in order to increase the efficiency of burning power-generating fuel by the example of burning lean Kuznetsk coal in a solid slag removal scheme. Combustion options have been proposed and investigated in schemes with direct injection of coal dust and with an intermediate coal dust hopper. The schemes use direct-flow burners with an counter-displaced arrangement and nozzles with a downward inclination, and staged combustion of fuel is used. A study of the furnace’s aerodynamics on an isothermal bench was carried out. The results of physical modeling were compared with the data of numerical modeling of an isothermal bench. It is noted that combustion schemes differ in the intensity of vortex formation in the active combustion zone. A numerical simulation of fuel combustion in the boiler furnace was performed using the two indicated combustion schemes. The purpose of the simulation was to obtain the distribution of temperatures, gas velocities, concentrations of combustion products, nitrogen oxide emissions, degree of burnout in the furnace volume and other characteristics that affect the efficiency, reliability, and environmental safety of the boiler. The results of model studies showed that the developed schemes provide high efficiency of burning lean Kuznetsk coal with solid slag removal and, at the same time, low emissions of nitrogen oxides. An additional verification of the numerical model was carried out by comparing the gas temperatures by the height of the furnace obtained by its numerical simulation and thermal zone calculations. A comparison of the temperatures of the gases at the outlet of each zone showed their good agreement (the difference was no more than 30°C).