Co-firing of biomass waste-derived syngas in coal power boiler

The paper deals with waste gasification as a technology allowing for indirect co-firing of large quantities of biodegradable wastes in coal-fired power boilers. In contrast to common landfilling and direct co-firing, gasification of wastes presents a number of advantages. Problematic species in original feedstocks can be partly safely incinerated in the furnace and partly retained in the gasification residues.     

PDA research on a novel pulverized coal combustion technology for a large utility boiler

In this paper, a new technology for a tangential firing pulverized coal boiler, high efficiency and low NO_x combustion technology with multiple air-staged and a large-angle counter flow fuel-rich jet (ACCT for short) is proposed. To verify the characteristics of this technology, experiments of two combustion technologies, ACCT and CFS-1 (Concentric Firing System-1), are carried out under a cold model of a 1025 t/h tangential firing boiler with a PDA (particle dynamics anemometer). The distributions of velocity, particle concentration, particle diameters and the particle volume flux of primary air and secondary air are obtained. The results show that the fuel-rich primary air of ACCT can go deeper into the furnace and mix with the main flow better, which means that the counter flow of fuel-rich jets in ACCT can realize stable combustion, low NO_x emission and slagging prevention.     

Research of boiler combustion regulation for reducing NOx emission and its effect on boiler efficiency

The effect of boiler combustion regulation on NO_x emission of two 1025t/h boilers has been studied.The re-searches show that NOx emission is influenced by coal species,operation conditions,etc,and can be reduced byregulating the combustion conditions.The effect of combustion regulation on boiler efficiency has also beenchecked.     

Numerical calculation on combustion process and NO transformation behavior in a coal-fired boiler blended ammonia: Effects of the injection position and blending ratio

Ammonia (NH₃), as a potential carbon-free alternative fuel, can be blended into coal-fired boiler to achieve significant pollution reduction and carbon reduction, but there are concerns about high NOx emissions due to high nitrogen content. According to the characteristics of coal/NH₃ co-combustion, a dual-fuel co-combustion model with strong adaptability and high accuracy was established in this study through Chemkin software to study the influence of different injection positions and blending ratios on combustion characteristics and NOx generation process. Then, the co-combustion model was applied to the three-dimensional CFD calculation process of a 330 MWe front-fired boiler, and the combustion characteristics, NOx distribution and reaction process were calculated when cal. 20% NH₃ was blended in the primary air. The results show that when cal. 20% NH₃ is blended, the change of NO content mainly occurs in ignition zone and flame zone, and the transformation behavior of N in NH₃ is optimized to a 15-step elementary reaction; The temperature distribution in the furnace is similar, and the average temperature at the furnace outlet decreases from 1033 °C to 988 °C, while NH₃ have a preferential combustion reaction with air than coal, resulting in a decrease in the burnout rate of coal; The NOx concentration at the furnace outlet decreases from 355 mg/Nm³ to 281 mg/Nm³, which is 20.85% lower than that under the pure coal burning condition, and the variation range of O₂ concentration and unburned NH₃ concentration is small.     

Combustion and NOx emissions characteristics of a down-fired 660-MWe utility boiler retro-fitted with air-surrounding-fuel concept

Air-surrounding-fuel is a well-known concept used within tangential and wall-fired boilers. Here, we report for the first time on industrial experiments performed to study the effects of this concept on a 660 MW_e full-scale down-fired boiler. Data are reported for the gas temperature distributions along the primary air and coal-mixed flows, furnace temperatures, gas compositions, for example O₂, CO and NO_x, and gas temperatures in the near-wall region. The influence of concentration control valve (CCV) opening on combustion and NO_x emission in the furnace were determined. The results show that the flame stability, temperature distribution, unburnt carbon are influenced by both concentration ratios and fuel-rich flow velocities. As CCV opening increases, NO_x emissions decrease from 2594 mg/m³ to 1895 mg/m³. Considering altogether economic benefits and environmental protection issues, 30% is the optimal value for the CCV opening.     

300MW对冲燃烧锅炉NOx排放特性及经济性试验研究

针对某电厂一台300 MW前后墙对冲燃烧锅炉,通过上层停运磨通入一次风,改变磨煤机组合、机组负荷、炉膛氧量以及一次风温、一次风量等参数,研究了不同燃烧方式对NOx排放及锅炉经济性的影响,提出了锅炉高效低污染运行的合理方式。     

Gas/particle flow and combustion characteristics and NOx emissions of a new swirl coal burner

Due to the limits of reserves and price for the high rank coal, the low rank coal has been employed as fuel for power generation in China and will be eventually employed in the world. To burn low rank coal, centrally fuel-rich swirl coal combustion burner has been studied in Harbin Institute of Technology. This paper reviews and analyzes the major research results. The work has included both experiments and numerical simulation. The experiments were conducted using small-scale single-phase experimental equipment, a gas/particle two-phase test facility and 200- and 300-MW_e wall-fired utility boilers. For the burner, the primary air and glass beads partially penetrate the central recirculation zone and are then deflected radially. At the center of the central recirculation zone, there is high particle volume flux and large particle size. For the burners the local mean CO concentrations, gas temperatures and temperature gradient are higher, and the mean concentrations of O₂ and NO_x in the jet flow direction in the burner region are lower. Moreover, the mean O₂ concentration is higher and the gas temperature and mean CO concentration are lower in the side wall region. Centrally fuel-rich burners have been successfully used in 200- and 300-MWe wall-fired pulverized coal utility boilers.     

Effects of pyrolyzed semi-char blend ratio on coal combustion and pollution emission in a 0.35 MW pulverized coal-fired furnace

The effects of blend ratio on combustion and pollution emission characteristics for co-combustion of Shenmu pyrolyzed semi-char (SC), i.e., residuals of the coal pyrolysis chemical processing, and Shenhua bituminous coal (SB) were investigated in a 0.35 MW pilot-scale pulverized coal-fired furnace. The gas temperature and concentrations of gaseous species (O₂, CO, CO₂, NO_x and HCN) were measured in the primary combustion zone at different blend ratios. It is found that the standoff distance of ignition changes monotonically from 132 to 384 mm with the increase in pyrolyzed semi-char blend ratio. The effects on the combustion characteristics may be neglected when the blend ratio is less than 30%. Above the 30% blend ratio, the increase in blend ratio postpones ignition in the primary stage and lowers the burnout rate. With the blend ratio increasing, NO_x emission at the furnace exit is smallest for the 30% blend ratio and highest for the 100% SC. The NO_x concentration was 425 mg/m³ at 6% O₂ and char burnout was 76.23% for the 45% blend ratio. The above results indicate that the change of standoff distance and NO_x emission were not obvious when the blend ratio of semi-char is less than 45%, and carbon burnout changed a little at all blend ratios. The goal of this study is to achieve blending combustion with a large proportion of semi-char without great changes in combustion characteristics. So, an SC blend ratio of no more than 45% can be suitable for the burning of semi-char.     

CO2 and pollutant emissions from passenger cars in China

In this paper, CO₂ and pollutant emissions of PCs in China from 2000 to 2005 were calculated based on a literature review and measured data. The future trends of PC emissions were also projected under three scenarios to explore the reduction potential of possible policy measures. Estimated baseline emissions of CO, HC, NO_x, PM₁₀ and CO₂ were respectively 3.16×10⁶, 5.14×10⁵, 3.56×10⁵, 0.83×10⁴ and 9.14×10⁷ tons for China’s PCs in 2005 with an uneven distribution among provinces. Under a no improvement (NI) scenario, PC emissions of CO, HC, NO_x, PM₁₀ and CO₂ in 2020 are respectively estimated to be 4.5, 2.5, 2.5, 7.9 and 8.0 times that of 2005. However, emissions other than CO₂ from PCs are estimated to decrease nearly 70% by 2020 compared to NI scenario mainly due to technological improvement linked to the vehicle emissions standards under a recent policy (RP) scenario. Fuel economy (FE) enhancement and the penetration of advanced propulsion/fuel systems could be co-benefit measures to control CO₂ and pollutant emissions for the mid and long terms. Significant variations were found in PC emission inventories between different studies primarily due to uncertainties in activity levels and/or emission factors (EF).     

Performance of a domestic pellet boiler as a function of operational loads: Part-2

Emissions and efficiency of a pellet boiler (40 kW) at nominal load were compared with emissions and efficiency at reduced load, while fired with six biomass pellets. The pellets include reed canary grass (Phalaris arundinacea), pectin waste from citrus shells (Citrus reticulata), sunflower husk (Helianthus annuus), peat, wheat straw (Triticum aestivum) and wood pellets. The measurements of emissions comprised of carbon monoxide (CO), nitrogen oxides (NO_x), sulphur oxides (SO_x) and flue dust mass concentrations (using DINplus and isokinetic sampling techniques). Emissions varied as a function of operational loads, for each type of pellets.The CO emissions were insignificant with reed canary grass (RCG), citrus pectin waste (CPW) and straw pellets at nominal load, however, at reduced load same pellets emitted 1.9, 4.0 and 7.4 times higher CO than wood pellets, respectively. Peat pellets emitted maximum CO at nominal load (4221.1 mgNm⁻³, 12.6 times higher than wood pellets) however; at reduced load CO emission was insignificant. The highest NO_x emissions were reported with CPW, which were 3.4 and 4.6 times higher than wood pellets at nominal load and reduced load, respectively. Dust emissions were highest with sunflower husk and lowest with RCG pellets, at both operational modes. The best performance was reported with wood pellets, followed by RCG and pectin pellets, however, wood pellets combustion emitted 1.7 and 2.0 times higher dust_DINplus than RCG at nominal and reduced loads, respectively. Not only fuel specific combustion optimization but also operational load specific optimization is essential for efficient use of agro-pellets in this type of boilers.     

Light vehicle energy efficiency programs and their impact on Brazilian CO2 emissions

This paper analyses the impact of an energy efficiency program for light vehicles in Brazil on emissions of carbon dioxide (CO₂), the main greenhouse gas in the atmosphere. Several energy efficiency programs for light vehicles around the world are reviewed. The cases of Japan and Europe were selected for presentation here given their status as current and future world leaders in the control of passenger vehicle fuel consumption. The launching of the National Climate Change Plan and the pressure on the Brazilian car industry due to the world financial crisis make it a good time for the Brazilian government to implement such a program, and its various benefits are highlighted in this study. Three scenarios are established for Brazil covering the 2000–2030 period: the first with no efficiency goals, the second with the Japanese goals applied with a 10 years delay, and the third, with the Japanese goals applied with no delay. The consequences of a vehicular efficiency program and its middle and long-term effects on the consumption of energy and the CO₂ emissions are quantified and discussed. The simulation results indicate that efficiency goals may make an important contribution to reducing vehicular emissions and fuel consumption in Brazil, compared to a baseline scenario.     

Impact of SO2 poisoning of platinum nanoparticles modified glassy carbon electrode on oxygen reduction

An extraordinary recovery characteristic of Pt-nanoparticles from SO₂ poisoning is introduced in this study. Platinum nanoparticles (nano-Pt) modified glassy carbon electrode (nano-Pt/GC) has been compared with polycrystalline platinum (poly-Pt) electrode towards SO₂ poisoning. Two procedures of recovery of the poisoned electrodes were achieved by cycling the potential in the narrow potential range (NPR, 0-0.8 V vs. Ag/AgCl/KCl (sat.)) and wide potential range (WPR, −0.2 to 1.3 V). The extent of recovery was marked using oxygen reduction reaction (ORR) as a probing reaction. SO₂ poisoning of the electrodes changed the mechanism of the oxygen reduction from the direct reduction to water to the stepwise reduction involving the formation of H₂O₂ as an intermediate, as indicated by the rotating ring-disk voltammetry. Using the WPR recovery procedure, it was found that two potential cycles were enough to recover 100% of the activity of the ORR on the nano-Pt/GC electrode. At the poly-Pt electrode, however, four potential cycles of the WPR caused only 79% in the current recovery, while the peak potential of the ORR was 130 mV negatively shifted as compared with the fresh poly-Pt electrode. Interestingly, the NPR procedure at the nano-Pt/GC electrode was even more efficient in the recovery than the WPR procedure at the poly-Pt electrode.     

上海气象因素对PM2.5等大气污染物浓度的影响

统计了上海市2013年6月至2014年5月PM_(2.5)、NO_2、SO_2月平均质量浓度和气象条件,分析了气温、风向、风力、降水量、湿度与污染物月平均质量浓度的相关性.结果发现:气温与污染物质量浓度呈负相关性;夏季的主导风向有利于污染物扩散和稀释,而冬季的主导风向则可引起污染物聚集;风力的增强有利于污染物扩散;降水是颗粒污染物沉降的方法之一,但在不产生降水的情况下湿度增大会造成二次气溶胶的生成,使得污染物质量浓度增加.     

Mechanism analysis on the pulverized coal combustion flame stability and NOx emission in a swirl burner with deep air staging

Low NOx burner and air staged combustion are widely applied to control NOx emission in coal-fired power plants. The gas-solid two-phase flow, pulverized coal combustion and NOx emission characteristics of a single low NOx swirl burner in an existing coal-fired boiler was numerically simulated to analyze the mechanisms of flame stability and in-flame NOx reduction. And the detailed NOx formation and reduction model under fuel rich conditions was employed to optimize NOx emissions for the low NOx burner with air staged combustion of different burner stoichiometric ratios. The results show that the specially-designed swirl burner structures including the pulverized coal concentrator, flame stabilizing ring and baffle plate create an ignition region of high gas temperature, proper oxygen concentration and high pulverized coal concentration near the annular recirculation zone at the burner outlet for flame stability. At the same time, the annular recirculation zone is generated between the primary and secondary air jets to promote the rapid ignition and combustion of pulverized coal particles to consume oxygen, and then a reducing region is formed as fuel-rich environment to contribute to in-flame NO_X reduction. Moreover, the NOx concentration at the outlet of the combustion chamber is greatly reduced when the deep air staged combustion with the burner stoichiometric ratio of 0.75 is adopted, and the CO concentration at the outlet of the combustion chamber can be maintained simultaneously at a low level through the over-fired air injection of high velocity to enhance the mixing of the fresh air with the flue gas, which can provide the optimal solution for lower NOx emission in the existing coal-fired boilers.     

China’s regional CO2 emissions: Characteristics,inter-regional transfer and emission reduction policies

This paper analyzes the characteristics of China’s regional CO₂ emissions and effects of economic growth and energy intensity using panel data from 1997 to 2009. The results show that there are remarkable regional disparities among eastern, central and western areas, regional elasticities of per capita GDP and energy intensity on CO₂ emissions, which reflect the regional differences in economic development, economy structure and restraining function of energy intensity decrease on the emission. Energy intensity reducing is more effective to emission abatement for provinces with higher elasticity of energy intensity, but may not be significant for provinces with lower elasticity. The inverse distribution of energy production and consumption, regional unfairness caused by institutional factors like energy price and tax system result in inter-regional CO₂ emission transfer embodied in the power transmission. The calculation indicates that the embodied emission transfer was gradually significant after 2003, from eastern area to the central and western areas, especially energy production provinces in central area, which leads to distortion on the emission and emission intensity. The regional emission reduction targets and supporting policies should be customized and consistent with the actual situations rather than setting the same target for all the provinces.     

Experimental studies on cofiring of coal and biomass blends in India

Concerns regarding the potential global environmental impacts of fossil fuels used in power generation and other energy supplies are increasing worldwide. One of the methods of mitigating these environmental impacts is increasing the fraction of renewable and sustainable energy in the national energy usage. A number of techniques and methods have been proposed for reducing gaseous emissions of NO_x,SO₂ and CO₂ from fossil fuel combustion and for reducing costs associated with these mitigation techniques. Some of the control methods are expensive and therefore increase production costs. Among the less expensive alternatives, cofiring has gained popularity with the electric utility producers. This paper discusses the ‘gaseous emission characteristics namely NO_x,SO₂, suspended particulate matter and other characteristics like specific fuel consumption, total fuel required, actual and equivalent evaporation, total cost of fuel, etc. from a 18.68 MW power plant with a travelling grate boiler, when biomass was cofired with bituminous coal in three proportions of 20%, 40% and 60% by mass. Bagasse, wood chips (Julia flora), sugarcane trash and coconut shell are the biomass fuels cofired with coal in this study.     

Integrated gas dynamic computational modelling and thermodynamic combustion diagnostics of multicylinder four-stroke spark ignition engine using compressed natural gas as a fuel

A comprehensive computational simulation model has been developed to describe the performance, efficiency and emission characteristics of the four-stroke multi-cylinder spark ignition engine which uses compressed natural gas as a fuel. This model performs an integrated simulation of thermodynamic, gas dynamic, and chemical kinetics of the whole engine system coupling with intake and exhaust manifolds. The thermodynamic combustion process is modelled by using the turbulent flame propagation process with a two-zone chamber (burned and unburned). Gas dynamics in the manifold system are modelled by using unsteady compressible hyperbolic partial differential equations. These equations contain heat transfer, friction, area change in pipe and empirical constants, which are used to determine boundary conditions at pipe junctions, valves and open ends. These equations are transferred into a set of ordinary differential equations by applying the method of characteristics and are solved by the finite difference method. Regarding exhaust emissions, nitric oxide concentrations have been predicted by using the rate kinetic model in the power cycle and along the exhaust pipes. Carbon monoxide is computed under the chemical equilibrium condition and then the empirical adjustment is made for kinetic behaviours based upon experimental results. Finally, predicted results of this model have been compared with experimental results and are found to be compatible. The parametric studies have been conducted with the equivalence ratio and the engine RPM, to predict engine performance. Also, the variations of pressure, temperature, and gas compositions in the exhaust system have been studied.     

Assessment of energy performance and air pollutant emissions in a diesel engine generator fueled with water-containing ethanol–biodiesel–diesel blend of fuels

Biomass based oxygenated fuels have been identified as possible replacement of fossil fuel due to pollutant emission reduction and decrease in over-reliance on fossil fuel energy. In this study, 4 v% water-containing ethanol was mixed with (65–90%) diesel using (5–30%) biodiesel (BD) and 1 v% butanol as stabilizer and co-solvent respectively. The fuels were tested against those of biodiesel–diesel fuel blends to investigate the effect of addition of water-containing ethanol for their energy efficiencies and pollutant emissions in a diesel-fueled engine generator. Experimental results indicated that the fuel blend mix containing 4 v% of water-containing ethanol, 1 v% butanol and 5–30 v% of biodiesel yielded stable blends after 30 days standing. BD1041 blend of fuel, which composed of 10 v% biodiesel, 4 v% of water-containing ethanol and 1 v% butanol demonstrated −0.45 to 1.6% increase in brake-specific fuel consumption (BSFC, mL kW⁻¹ h⁻¹) as compared to conventional diesel. The better engine performance of BD1041 was as a result of complete combustion, and lower reaction temperature based on the water cooling effect, which reduced emissions to 2.8–6.0% for NO_x, 12.6–23.7% particulate matter (PM), 20.4–23.8% total polycyclic aromatic hydrocarbons (PAHs), and 30.8–42.9% total BaPeq between idle mode and 3.2 kW power output of the diesel engine generator. The study indicated that blending diesel with water-containing ethanol could achieve the goal of more green sustainability.     

Efficiency of European emissions markets: Lessons and implications

While prior studies have shown that emission rights and futures contracts on emission rights are efficiently priced, there are no studies on the efficiency of the options market. Therefore, this study fills the gap. We examine empirical evidence regarding the efficiency of the options market for emissions rights in Europe. We employ the put-call parity approach to test the efficiency of options on emission rights traded in the European market. This implies that firms can trade options on emission rights in addition to other existing strategies in order to manage their greenhouse gas emissions.     

Decomposition of CO2 emissions change from energy consumption in Brazil: Challenges and policy implications

This study evaluates the changes in CO₂ emissions from energy consumption in Brazil for the period 1970–2009. Emissions are decomposed into production and consumption activities allowing computing the full set of energy sources consumed in the country. This study aims to develop a comprehensive and updated picture of the underlying determinants of emissions change from energy consumption in Brazil along the last four decades, including for the first time the recently released data for 2009. Results demonstrate that economic activity and demographic pressure are the leading forces explaining emission increase. On the other hand, carbon intensity reductions and diversification of energy mix towards cleaner sources are the main factors contributing to emission mitigation, which are also the driving factors responsible for the observed decoupling between CO₂ emissions and economic growth after 2004. The cyclical patterns of energy intensity and economy structure are associated to both increments and mitigation on total emission change depending on the interval. The evidences demonstrate that Brazilian efforts to reduce emissions are concentrated on energy mix diversification and carbon intensity control while technology intensive alternatives like energy intensity has not demonstrated relevant progress. Residential sector displays a marginal weight in the total emission change.