Ultra-low Emission Research Articles

Indocyanine green based fluorescence imaging improved by deep learning.

Intraoperative identification of malignancies using indocyanine green (ICG) based fluorescence imaging could provide real-time guidance for surgeons.Existing ICG-based fluorescence imaging mostly operates in the NIR-I (700-1,000 nm) or the NIR-IIa' windows (1,000-1,300 nm), which not optimal in terms of spatial resolution and contrast since their light scattering is higher than the NIR-IIb window (1,500-1,700 nm). It is highly desired to achieve ICG-based fluorescence imaging in the NIR-IIb window, but it is hindered by its ultra-low NIR-IIb emission tail of ICG. Herein we employ a generative adversarial network (GAN) to generate NIR-IIb ICG images directly from the acquired NIR-I ICG images. This approach was investigated by in vivo imaging of sub-surface vascular, intestine structure, and tumors, and their results demonstrated significant improvement in spatial resolution and contrast for ICG-based fluorescence imaging. It is potential for deep learning to improve ICG-based fluorescence imaging in clinical diagnostics and image-guided surgery in clinics. This article is protected by copyright. All rights reserved.

Comprehensive energy efficiency analysis of ultra-supercritical thermal power units

At present, ultra-supercritical power plant is the most advanced technology, which can achieve ultra-low pollutant emissions and greatly improve the energy efficiency of power plant. In this paper, the key factors affecting the energy efficiency of thermal power unit are analyzed. Moreover, the way in which these factors affect the energy efficiency of thermal power unit is obtained. Besides, this study lay a solid foundation for subsequent improvements in the energy efficiency of thermal power unit. First, a mathematical mechanism model of ultra-supercritical thermal power units is established. In addition, Aspen Plus software is used to build a full process simulation model of thermal power unit. In addition, a methodology for energy efficiency analysis based on the exergy balance theory is presented, and energy efficiency evaluation indicators are defined. Finally, the TOPSIS method was used to rank the key factors affecting the energy efficiency of thermal power unit. Based on experimental analysis, this study found that in comparison to general unit, the ultra-supercritical thermal power units has improved boiler efficiency by approximately 2%, power generation efficiency by approximately 6.77%, carbon emissions by approximately 0.027 t/h and the exergy efficiency by approximately 2.91%, providing better energy efficiency and lower carbon emissions.

Effects of hydrogen and EGR on energy efficiency improvement with ultra low emissions in a common rail direct injection compression ignition engine fueled with dimethyl ether (DME) under HCCI mode

This study deals with enhancing the energy efficiency with ultra-low emissions and extending the operating range (maximum load limit) of dimethyl ether (DME) fueled homogeneous charge compression ignition (HCCI) engine using hydrogen and exhaust gas recirculation (EGR). In the neat DME mode, the possible maximum load limit with controlled auto-ignition (CAI) was found as 24% (BMEP of 1.67 bar). Beyond 24% load, the knocking was observed with an advanced combustion phase, and shortened combustion duration resulted in uncontrolled auto-ignition (UAI) combustion. The addition of EGR extended the maximum load limit to 52% (BMEP of 3.62 bar) (60% EGR). Near-zero levels of NOx, zero smoke, and marginal CO and HC emissions reduction were observed with the optimized EGR rate (35%). The hydrogen fuel addition along with DME at an optimized EGR rate resulted in combustion phase retardation with the elimination of the low-temperature reaction (LTR) region. The energy efficiency (EE) and indicated thermal efficiency (ITE) increased along with zero smoke emission, ultra-low NOx, CO, and HC, and lower CO2 emissions till 12% of hydrogen energy share (HES). Thus, the combined strategy of EGR and hydrogen could effectively extend the operating range with ultra-low emissions levels.

Cost-benefits analysis of ultra-low emissions standard on air quality and health impact in thermal power plants in China

As China's largest energy infrastructure, thermal power plant consumed approximately half of China's coal over the past decade and threatened air quality, human health and socioeconomic development. Thus, a series of control policies have been implemented to alleviate those impacts in China. Particularly, China has witnessed unprecedented declines in air pollutant emissions from thermal power plants since the ultra-low emissions (ULE) standards were implemented. In contrast, the effect of the ULE policy on air quality, health and cost benefits remains poorly understood. Therefore, this study estimates the improved air quality and associated health and economic benefits under the ULE standards in the thermal power sector by using a measure-specific approach, combining a bottom-up emission inventory, an atmospheric model, a health assessment model and a cost analysis model. The results show that all the control measures lead to reduced air pollution, and renovating pre-existing units (RPU) is the most effective. Compared to without implementing the ULE policy, the population-weighted average PM2.5 and O3 concentrations decreased by 1.50 μg/m3 and 0.87 ppm, and 67,831 premature deaths could be avoided nationally. Furthermore, the results also show the net economic benefits of combining health benefits and costs due to control measures are 109.92 billion Yuan (in 2015 value) in China. The comprehensive results reveal that the health benefits outweigh the direct policy. Based on these empirical findings and the specific circumstances of China, we suggest that RPU should be further promoted to the entire of China, and if necessary, establish a long-term compensation mechanism for inter-provincial interests and institute and enforce comprehensive policies that carefully consider the health impacts of policies. This study provides strong arguments for China's policy-making and considering tightening emission standards for thermal power plants worldwide.

Ultra-low emission power generation utilizing chemically stabilized waste plastics pyrolysis oil in RCCI combustion concept

Emission standards in European Union, designed to reduce the environmental impact of power generation, present a significant challenge for fast-response distributed power generation systems based on internal combustion engines. Regulated emissions, such as NOx and particulate matter present a major concern due to their adverse number of environmental and health effects. Simultaneously, European Union strives towards sustainable management of plastic waste and seeks the ways for its upcycling and production of new fuels and chemicals. As an answer to the presented challenges, the present experimental study addresses the potential for use of chemically stabilized Waste Plastics Oil (WPO), a product of pyrolysis process of waste plastics in a Reactivity Controlled Compression Ignition (RCCI) combustion concept. To establish a reactivity-controlled combustion, the study uses a combination of methane (a model fuel for biomethane) and WPO to a) simultaneously reduce NOx and particulate matter emissions due to low local combustion temperatures and a high degree of charge homogenization and b) address waste and carbon footprint reduction challenges. Through experiments, influence of direct injection timing and energy shares of utilized fuels to in-cylinder thermodynamic parameters and engine emission response were evaluated in engine operating points at constant indicated mean effective pressure. Acquired results were deeply investigated and benchmarked against compression ignition (CI) and RCCI operation with conventional diesel fuel to determine potential for WPO utilization in an advanced low-temperature combustion concept. Results show that chemically stabilized WPO can be efficiently utilized in RCCI combustion concept without adaptation of injection parameters and that with suitable control parameters, ultra-low emissions of NOx and PM can be achieved with utilized fuels. For diesel/methane mix, NOx and PM emissions were reduced compared to conventional CI operation for 82.0% and 93.2%, respectively, whereas for WPO/methane mix, NOx and PM emissions were reduced for 88.7% and 97.6%, respectively, which can be ascribed to favourable chemical characteristics of WPO for the utilized combustion concept. In the least favourable operating point among those studied, indicated mean effective pressure covariance was kept below 2.5%, which is well below 5% being considered the limit for stable engine operation.

Numerical study of the effects of excess air ratio on passive pre-chamber jet performance and ignition mechanism

Pre-chamber (PC) ignition is a promising lean-burn technology to improve the efficiency of spark ignition (SI) engines while achieving ultra-low NOx emissions. However, the significant effects of the excess air ratio (λ) on the PC jet performance and ignition mechanism were still not fully unraveled. The current study numerically investigated the jet characteristics and combustion behaviors of a narrow-throat PC with two rows of orifices on a passive PC engine fueled with methane. The numerical model was validated extensively by the pressure, heat release rate, and natural flame luminosity (NFL) imaging of the PC flame jet. A detailed comparison of the NFL images of the jets and the simulated flame iso-faces presented excellent matching in the flame jet penetration and propagation process. The results reveal that the λ = 0.9 case has the best jet performance, but it doesn’t lead in every jet characteristic. For instance, the jet temperature is highest under λ = 1.0, and OH concentration is most under λ = 1.1. The transition from cold jet to flame jet produces noticeable jet non-uniformity, which is reported for the first time. This observation can be remarked as a more accurate indication of the initiation of pre-chamber flame jet discharge. The asymmetrical mixture inflow from the main chamber produces asymmetrical turbulent kinetic energy (TKE) and temperature distributions; these result in different flame propagation in the PC, jet non-uniformity, and varied stages of jet discharge. The upper jets are quenched in every case because of the much higher TKE, while the lower jets don’t present quenching when the λ ranges from 0.9 to 1.3; especially, the λ = 1.1 case has the best ignition performance for its most OH radicals. The “jet ignition regime”, in which flame quenching takes place, results in highly non-uniform flame propagation and low flame propagation speed. The ultra-rich case shows more signs of jet ignition and thus exhibits worse jet performance than the lean cases. This study uncovers the mechanisms and the optimal λ value for the pre-chamber ignition of the main chamber charge, providing valuable guidance for PC design.

Experimental study on pulverized coal swirl-opposed combustion preheated by a circulating fluidized bed. Part A. Wide-load operation and low-NOx emission characteristics

In this study, the operating characteristics and NOx emission patterns are explored under a wide load range based on a 2MWth pulverized coal preheated combustion test platform. Preheated char with high physical sensible heat and preheated gas with high calorific value greatly improve the ignition and stability of the combustion characteristics of pulverized coal at low loads. Moreover, performing pre-denitrification during the preheating process helps to lower NOx emissions. Stable operation at a wide load range of 26%–106% was achieved, and ultralow loads of 40% and 26% were achieved when the pre-circulating fluidized bed (PCFB) was operated in double-/single-sided operation mode, respectively. Meanwhile, uniform concentration and temperature fields were achieved when both/one side of the PCFB were/was in operation. When operating on the double side of the PCFB, ultralow NOx emissions (@6% O2) of 39.9 mg/m3 and 43.7 mg/m3 were achieved at 40% and 50% loads, respectively. When operating on a single side, the NOx emission amount was 28.3 mg/m3 at 26% load. Furthermore, when the swirling air and the bottom air are equally distributed, the secondary air equivalent ratio is appropriately increased, and the injection position of the burnout air is properly delayed, NOx emissions are reduced.

Clearing the Air: Assessing the Effectiveness of Emission Policy in Qinhuangdao’s Key Industries

China has successively put forward ultra-low emission (ULE) transformation plans to reduce the air pollutant emissions of industrial pollutants since 2014. To assess the benefits of the ULE policy on regional air quality for Qinhuangdao, this study developed an emission inventory of nine atmospheric pollutants in 2016 and evaluated the effectiveness of the emission policy in Qinhuangdao’s key industries under different scenarios with an air quality model (CALPUFF). The emissions of air pollutants in 2016 were as follows: Sulfur dioxide (SO2) emitted 48.91 kt/year, nitrogen oxide (NOx) emitted 86.83 kt/year, volatile organic compounds (VOCs) emitted 52.69 kt/year, particulate matter (PM10 and PM2.5) emitted 302.01 and 116.85 kt/year, carbon monoxide (CO) emitted 1208.80 kt/year, ammonia (NH3) emitted 62.87 kt/year, black carbon (BC) emitted 3.79 kt/year, and organic carbon (OC) emitted 2.72 kt/year, respectively. The results showed that at the regional level in 2025, the iron and steel industry under the PPC (Peak Production Capacity) scenario had the highest potential for reducing SO2 and NOx emissions, while the cement industry under the PPC scenario excelled in reducing PM10 emissions. As for the industrial level in 2025, the flat glass industry under the ULE scenario would reduce the most SO2 emitted, while the iron and steel industry and the cement industry under the PPC scenario demonstrated the best reduction in NOx and PM10 emissions, respectively. Furthermore, the average annual contribution concentration of SO2, NOx, and PM10 in the air monitoring stations of Qinhuangdao under the PPC scenario was significantly lower than that under the BAU scenario revealed by air quality simulation. It can be concluded that the emission policy in Qinhuangdao will help improve the air quality. This study can provide scientific support for policymakers to implement the ULE policy in industrial undeveloped cities and tourist cities such as Qinhuangdao in the future.

Complete X-ray census of M dwarfs in the solar neighborhood

Context. X-ray emission is the most sensitive diagnostic of magnetic activity in M dwarfs and, hence, of the dynamo in low-mass stars. Moreover it is crucial for quantifying the influence of the stellar irradiation on the evolution of planet atmospheres. Aims. We have embarked in a systematic study of the X-ray emission in a volume-limited sample of M dwarf stars to explore the full range of activity levels present in their coronae. We look to obtain a better understanding of the conditions in their outer atmospheres and their possible impact on the circumstellar environment. Methods. Based on a recent catalog of Gaia objects within 10 pc from the Sun, we identified all its stars with spectral types between M0 and M4 and we carried out a systematic search for X-ray measurements of this sample. To this end, we used both archival data from ROSAT, XMM-Newton, and the ROentgen Survey with an Imaging Telescope Array (eROSITA) on board the Russian Spektrum-Roentgen-Gamma mission, as well as our own dedicated XMM-Newton observations. To make inferences on the properties of the M dwarf corona, we compared the range of their observed X-ray emission levels to the flux radiated by the Sun from different types of magnetic structures: coronal holes, background corona, active regions, and cores of active regions. In this work, we focus on the properties of stars with the faintest X-ray emission. Results. At the current state of our project, with more than 90% of the 10 pc M dwarf sample observed in the X-ray, there is only one star that has had no detections: GJ 745 A. With an upper limit luminosity of log Lx (erg s−1) < 25.4 and an X-ray surface flux of log FX,SURF (erg cm−2 s−1) < 3.6, GJ 745 A defines the lower boundary of the X-ray emission level for M dwarfs. Together with its proper motion companion (GJ 745 B), it is the only star in this volume-complete sample located in the range of X-ray surface flux that corresponds to the faintest solar coronal structures, namely: coronal holes. The fact that the ultra-low X-ray emission level of GJ 745 B (log Lx (erg s−1) = 25.6 and log FX,SURF (erg cm−2 s−1) = 3.8) is entirely attributed to flaring activity indicates that while its corona is dominated by “holes,” at least one magnetically active structure is present. This structure determines the total X-ray brightness and the coronal temperature of the star.

A continuous polytetrafluoroethylene foam-coating to glass fiber mat with superior self-cleaning, antistatic and high filtration efficiency performances

Air pollution has become a significant global environmental issue, leading to adverse health effects and respiratory diseases. To address this challenge, expanded polytetrafluoroethylene (ePTFE) membrane-based fibrous filters have gained popularity in the past decade. However, the thinness and low mechanical strength of ePTFE membranes make them susceptible to damage from particle collisions. As an alternative to ePTFE membranes, PTFE emulsion has emerged as a promising approach to enhance filtration efficiency. However, due to PTFE's low surface energy and high crystallinity, it is difficult for PTFE to self-bond into a membranes and adhere to substrates. Therefore, the filtration efficiency of PTFE-impregnated filter materials does not meet the requirements for ultra-low emissions, and they have poor wear resistance, resulting in a short service life. Herein, we fabricate a PTFE emulsion foam-coating membrane filter. The influences of the contents of PVA on the film morphology, air permeability, pore size and distribution, abrasive resistance and antistatic properties were analyzed. The self-cleaning performance was simulated and the filtration performance was measured as well. Notably, the frictional mass loss index of the PTFE emulsion foam-coating membrane filter was 0.07. After 30 cycles, the filtration efficiency was 98.93%, and the strip ratio was 91.03%. Our design of the PTFE emulsion foam-coating provided a new direction for the application of PTFE emulsion in the filtration field with superior self-cleaning, antistatic and high filtration efficiency performances.

Flame emission spectroscopy analysis of distributed liquid fuel combustion

Distributed combustion offers ultra-low pollutant emission, low susceptibility of thermoacoustic instabilities, and is highly fuel flexible, being an ideal choice for, e.g., boilers, furnaces, and gas turbines. It was recently demonstrated that Mixture Temperature-Control could also achieve distributed combustion and not restricted to Moderate or Intense, Low-oxygen Dilution combustion. The former approach is employed in the present paper. Online flame control is required by the need for dynamic operation, which is often performed via spectral flame measurements. Presently, the distribution of OH*, CH*, C2*, O2*, and two H2O* chemiluminescent emission peaks were evaluated; the first two represent ignition, while the latter four appear later in the reaction zone. Characteristics of distributed flames are compared to those of straight and V-shaped flames, which are well-known in the literature. The following observations were made. Distributed combustion is lifted and occupies the entire cross-section of the combustion chamber without featuring a characteristic shape. The OH*/CH* ratio shows a low dependence on the equivalence ratio, and the reactions start only 50 mm downstream of the burner lip. The dominant radical was CH* for all distributed flames. As the equivalence ratio increases, the reaction zone moves slightly upstream.

MXene based Janus fabrics with radiative heating towards efficient personal thermal management

Smart textiles for personal thermal management achieved by regulating multi-wavelength radiative characteristics of fabrics are highly demanded since they are potentially energy efficient, convenient and even fashionable. Herein, we report a Janus fabric for radiative heating by taking full advantages of MXene’s dual characteristics of ultralow mid-infrared emission and high photothermal conversion ability. After brush-coating a MXene layer on one side of a commercial polyamide fabric substrate, the Janus fabric enables 3.4 ℃ temperature increase of the simulated skin by suppressing body radiation loss. Meanwhile, the Janus fabric demonstrates superior photothermal conversion efficiency (13%) and photothermal heating performance, achieving 14.2 ℃ temperature increase under one sun irradiation. By virtue of the robust substrate and lightweight coating, the Janus fabric possesses satisfactory wearability (i.e., mechanical strength, flexibility, permeability), making the fabric be able to heat human body in practical uses. The efficient and durable Janus fabric provides a great potential of future all-day personal thermal management fabrics which can be applied in wide scenarios.

Research on The Ultra-Low Emission Technology in Internal Combustion Engine

Increasing the efficiency of internal combustion engines is a technologically proven and cost effective approach to dramatically improving the fuel economy of the nation’s fleet of vehicles in the near- to midterm, with the corresponding benefits of reducing our dependence on foreign oil and reducing carbon emissions. This review paper discusses on the research of ultra-low emission technology in internal combustion engine. Efficiency can be increased by improving combustion processes, minimizing engine losses such as friction, reducing the energy penalty of the emission control system and using recovered waste energy in propulsion. Compliance with exhaust emission regulations will be mandated and requires after-treatment technologies integrated with the engine combustion approaches. Fuels under consideration include hydrocarbon-based. Because of their relatively low cost, high performance, and ability to utilize renewable fuels, internal combustion engines, including those in hybrid vehicles, will continue to be critical to our transportation infrastructure for decades.

Potential of the reverse-reactivity controlled compression ignition (R-RCCI) combustion for maintaining ultra-low emissions and enhanced thermal efficiency

Focusing on the reverse-reactivity controlled compression ignition (R-RCCI) concept, the intake and fuel supply parameters were optimized using a promoted genetic algorithm combined with the computational fluid dynamics simulation in this investigation. The combustion characteristics and energy utilization of both gasoline partially premixed combustion (PPC) and polyoxymethylene dimethyl ethers (PODEn)/gasoline R-RCCI were further evaluated in detail. The results indicated that R-RCCI exhibits superior performance compared with PPC. The optimized gross indicated thermal efficiency (ITE) of R-RCCI is 3.9% and 2.6% higher than that of PPC under 4 and 7 bar indicated mean effective pressures (IMEPs), respectively. The premixed high-reactivity PODEn in R-RCCI decreases the needed intake temperature, which provides more flexibility for the combustion phasing control. This correspondingly results in improved thermal efficiency for R-RCCI at 4 bar IMEP. Meanwhile, the lower intake temperature helps to decrease the heat transfer loss under 7 bar IMEP. Moreover, R-RCCI exhibits significant superiority over PPC on the unburned hydrocarbon (HC), carbon monoxide (CO), nitrogen oxides (NOx), and soot emissions under the operating conditions investigated in this work. For R-RCCI, the pre-combustion of PODEn can create a thermal atmosphere containing accumulated oxygen radicals, which provides the reaction conditions for the subsequent gasoline oxidation.

Dynamic Modeling of Flue Gas Desulfurization Process via Bivariate EMD-Based Temporal Convolutional Network

Sulfur dioxide (SO2) can cause detrimental impacts on the ecosystem. It is well known that coal-fired power plants play a dominant role in SO2 emissions, and consequently industrial flue gas desulfurization (IFGD) systems are widely used in coal-fired power plants. To remove SO2 effectively such that ultra-low emission standard can be satisfied, IFGD modeling has become urgently necessary. IFGD is a chemical process with long-term dependencies between time steps, and it typically exhibits strong non-linear behavior. Furthermore, the process is rendered non-stationary due to frequent changes in boiler loads. The above-mentioned properties make IFGD process modeling a truly formidable problem, since the chosen model should have the capability of learning long-term dependencies, non-linear dynamics and non-stationary processes simultaneously. Previous research in this area fails to take all the above points into account at a time, and this calls for a novel modeling approach so that satisfactory modeling performance can be achieved. In this work, a novel bivariate empirical mode decomposition (BEMD)-based temporal convolutional network (TCN) approach is proposed. In our approach, BEMD is employed to generate relatively stationary processes, while TCN, which possesses long-term memory ability and uses dilated causal convolutions, serves to model each subprocess. Our method was validated using the operating data from the desulfurization system of a coal-fired power station in China. Simulation results show that our approach yields desirable performance, which demonstrates its effectiveness in the IFGD dynamic modeling problem.

Study on the Effects of Wet Flue Gas Desulfurization on Particulate Matter Emission from Industrial Coal-Fired Power Plants

This study aimed to investigate the effects of wet flue gas desulfurization (WFGD) on particulate matter (PM) emissions in coal-fired power plants (CFPPs) using an electrical low-pressure impactor (ELPI). The investigation was conducted on five industrial CFPPs of various loads in China to clarify the influence factors of WFGD on PM10 emissions. After WFGD, the proportion of PM2.5 to PM10 in the outlet flue gas increases, which showed that the WFGD system is selective in the capture of PM, with a significant effect on the capture of large particle sizes. The investigation found that four spray layers have a better effect on the capture of particles than two spray layers. Additionally, the investigation also found that unit load is not the main factor affecting the efficiency of PM10 capture by WFGD. Instead, the factors affecting the capture efficiency of PM10 by WFGD are the inlet flue gas temperature and the dust concentration. Relatively higher inlet flue gas temperature and lower inlet dust concentration will both result in higher emission of PM0.1~1 from the WFGD outlet. These findings suggest that a matched integration of WFGD and CFPP is essential for ultra-low PM emission control and green industry development.

Combustion and emission characteristics of hydrotreated pyrolysis oil on a heavy-duty engine

Second-generation biofuel is promising to be applied in the field of long-haul transportation, aviation, and marine shipping. This work focuses on the ignition behavior, combustion process, and emission characteristics of hydrotreated pyrolysis oil. This biomass-derived oil was blended with marine gas oil from 10 to 30 wt% without a co-solvent or emulsifier. Tests were performed both on a combustion research unit and a commercial heavy-duty diesel engine setup. The results from the combustion research unit reveal that ignition delay increase as hydrotreated pyrolysis oil blend ratio increases at tested ambient conditions. Engine tests were first performed under factory settings at representative load/speed points based on the European stationary test cycle for benchmarking. Then start of injection and fuel pressure are varied to check the controllability and engine sensitivity of hydrotreated pyrolysis oil blends. It is shown that under engine conditions, the combustion characteristics and heat release are quite identical among hydrotreated pyrolysis oil blends and diesel. Though all cases present ultra-low particulate matter emissions, hydrotreated pyrolysis oil blends yield higher particulate matter emissions, which increase as the blend ratio increases. The particulate matter/NOx tradeoff is observed both for benchmarking tests and parameter study. The results indicate that the engine can run with HPO blends smoothly and safely without major modification.

Numerical Study of Critical Recirculation Ratio for Achieving Unconditional MILD Combustion

Moderate or Intense Low Oxygen Dilution (MILD) combustion is a regime in which fuels burn in a distributed reaction zone generating ultra-low emissions and no visible flame front. Also known as flameless combustion, it can be achieved by recirculating flue gases into the reaction zone. A recirculation factor based on the mass recirculated is used to characterize a flameless regime. However, the original definition of MILD is based on the temperature levels of a reactor. This work connects both criteria by introducing a parameter called recirculation ratio derived theoretically from a mass balance. The ratio was numerically calculated by simulating a network of perfectly stirred reactors and performing an energy balance using open-source software. This methodology was validated against experimental and simulated data from the literature. Simulations were carried out for methane, ethane, propane, and hydrogen under adiabatic conditions and equivalence ratios from 0.6 to 1. Results indicate that a critical recirculation ratio is required for establishing unconditional MILD combustion, which changes with fuel type and equivalence ratio. In all cases studied, the critical ratio diminishes as the equivalence ratio is reduced. Hydrogen and methane require the highest and lowest critical ratio, respectively. Results suggest that externally diluting hydrogen with carbon dioxide could potentially reduce recirculation requirements for MILD combustion.

Improved Anthropogenic Mercury Emission Inventories for China from 1980 to 2020: Toward More Accurate Effectiveness Evaluation for the Minamata Convention.

Anthropogenic mercury (Hg) emission inventories are crucial for the effectiveness evaluation of the Minamata Convention on Mercury. In this study, we developed an integrated Dynamic Inventory for Mercury Emission (DIME) model and improved the accuracy of emission estimates for primary sources in China. Long-term historical speciated Hg emission inventories for China were established. The total Hg emissions increased from 217.0 t in 1980 to 357.8 t in 2020 with a peak value of 506.6 t in 2010. Three stages with distinct leading drivers were identified. At Stage 1 (1980-1997), Hg emissions doubled with the rapid growth of economy; the driver was offset by the increase of dust and SO2 control measures at Stage 2 (1997-2010) except for cement production; and co-benefits from strict control measures induced the decoupling of Hg emissions from the economy at Stage 3 (2010-2020). The ultralow emission (ULE) retrofits in key industries had pronounced Hg removal efficiencies. Large emission reduction potential still exists in the cement industry. The improved emission estimation methods for key sectors, the consistency in methodology for historical Hg emission inventories, and the more accurate spatial distribution of speciated Hg emissions in this study provide a practical toolkit for the effectiveness evaluation of the Minamata Convention.

Incorporation of fuel cell in oil refinery a step to achieve net zero-carbon emission goal

The usage of fuel cells is growing rapidly in various industries, and employing it as an alternative power source in oil refineries which will assist many large oil firms in achieving the global energy transition. The present paper focusses on significant utilization of fuel cell in downstream refinery to reach sustainable energy pathway towards net zero emission. The combination of gas turbine technology with high temperature fuel cells provides a power generating platform with ultra-high efficiency, ultra-low emissions, and fuel flexibility. Advances in R & D helps in reducing the cost of fuel cell and are now being used to power fuel cell producing energy ranging from 1 Watt to 10 Megawatt. The auxiliary power supplies and heat energy needed in refineries can be replaced by the use of these fuel cell. Fuel cell can be used in conjunction with the gas turbine for power supply with greater efficiency and lesser use of hydrocarbon-based fuel especially in equipments such as hydrotreater, desalting unit, pump and compressor unit etc. The heat generation in the fuel cell is associated with voltage losses and this generated heat can be used in reformer for hydrogen production, for space heating and preheating the steam required for heating of crude in crude oil distillation unit, vacuum jet, power turbines etc. With virtually zero harmful emission, minimal amount of space and higher efficiency reaching up to 60 %, the fuel cell can be utilized for optimum energy distribution in auxiliary units used in refinery.