Emission Control Systems Research Articles

An optimal hybrid emission control system in a multiple compliance period model

We characterize an optimal hybrid policy for pollutant emissions that includes a permit price ceiling and emission cap in a multi-period model. Previous studies have primarily focused on a hybrid policy of emission regulation that included an emission cap and permit price ceiling in a single period model, we extend this literature by developing such an optimal hybrid model in a multi-period framework where banking and borrowing of emission permits is allowed. In our model, we compare the case of a regulator who sets the emission cap and price ceiling to be consistent with a long run emission objective with the case of a regulator who occasionally is motivated to deviate from the optimal long run regulatory policy in order to correct for unexpected but exceptionally high emissions. Using a discrete dynamic programming model with stochastic emissions, we show that the hybrid model gives the regulator a degree of freedom in making an optimal price and quantity choice.

New emission deterioration rates for gasoline cars – Results from long-term measurements

Vehicle emission control systems have been found to degrade with use resulting in increasing emission rates with vehicle age. Standard European data for deterioration factors have only been based on a sample of vehicles with limited high mileage ranges, with only few Euro 3 and Euro 4 vehicles, and on laboratory tests only. Here we present deterioration rates derived from more than 110′000 records collected over the past thirteen years from on-road emission remote sensing in Zurich/Switzerland. Deterioration rates for hot NOx and CO emissions of older gasoline vehicles are much lower than assumed so far, but significantly higher for Euro 3 and Euro 4 cars. There is no evidence of high emitters but equipment gradually degrades across the fleet. Deterioration rates do not seem to depend on engine load. Routine idle emission tests have not resulted in measurable emission reductions of the inspected vehicles. National emission inventories should be updated in the light of this new data.

Gaseous emissions from a heavy-duty engine equipped with SCR aftertreatment system and fuelled with diesel and biodiesel: Assessment of pollutant dispersion and health risk

The changes in the composition of fuels in combination with selective catalytic reduction (SCR) emission control systems bring new insights into the emission of gaseous and particulate pollutants. The major goal of our study was to quantify NOx, NO, NO2, NH3 and N2O emissions from a four-cylinder diesel engine operated with diesel and a blend of 20% soybean biodiesel. Exhaust fume samples were collected from bench dynamometer tests using a heavy-duty diesel engine equipped with SCR. The target gases were quantified by means of Fourier transform infrared spectrometry (FTIR). The use of biodiesel blend presented lower concentrations in the exhaust fumes than using ultra-low sulfur diesel. NOx and NO concentrations were 68% to 93% lower in all experiments using SCR, when compared to no exhaust aftertreatment. All fuels increased NH3 and N2O emission due to SCR, a precursor secondary aerosol, and major greenhouse gas, respectively. An AERMOD dispersion model analysis was performed on each compound results for the City of Curitiba, assumed to have a bus fleet equipped with diesel engines and SCR system, in winter and summer seasons. The health risks of the target gases were assessed using the Risk Assessment Information System For 1-h exposure of NH3, considering the use of low sulfur diesel in buses equipped with SCR, the results indicated low risk to develop a chronic non-cancer disease. The NOx and NO emissions were the lowest when SCR was used; however, it yielded the highest NH3 concentration. The current results have paramount importance, mainly for countries that have not yet adopted the Euro V emission standards like China, India, Australia, or Russia, as well as those already adopting it. These findings are equally important for government agencies to alert the need of improvements in aftertreatment technologies to reduce pollutants emissions.

High‐Throughput Screening Technology for Automotive Applications

AbstractThe development of advanced emission control systems to meet the strict regulations requires efficient and flexible material screening capabilities. Here, a high throughput test unit is described. Two case studies demonstrate the rapid screening of relevant parameter spaces and material functionalities which can be used in product development. One involves steady‐state testing of hydrocarbon oxidation in Diesel aftertreatment systems, while the other shows the evaluation of oxygen storage capacity in the optimization of three‐way catalysts for gasoline engines.

Conception of an environmental technology data bank

For documentation, analysis and application of the state of the art and its development in environmental technologies, an information system should be conceived by using modern information and communication techniques. Within this project the pilot phase is being carried out, in which in co–operation with the established working party (industry, host and authorities) a test data bank is being implemented including emission control technologies of combustion systems, which emphasises the experience of applied emission control systems. For the model description of the emission control technologies into the data bank a special method was developed. Moreover a user structure system is shown, which allows for efficient access to the information without using a separate search language.

Development of Real-Time Platform for Engine Emission Control System

In order to obtain engine emission data, one engine data acquisition platform was built, NOx data which in exhaust was obtained respectively by exhaust gas sampling analysis and sensor real-time measure, verified the feasibility of real-time platform after comparison and analysis.

Deep oxidative desulfurization of liquid fuels

Abstract Increase in energy demand and consumption has been accompanied by a corresponding increase in sulfur emissions. These pollutants have both health and economic consequences. Furthermore, it significantly reduces the efficiency of advanced emission control systems of diesel engines, thereby indirectly causing more harm to the environment. This resulted in stringent sulfur emission limit down to about 15 ppm or less and in turn served as an incentive for research into alternative sulfur reduction technologies. Although feasible improvements to hydrodesulfurization are currently under investigation, adsorptive, extractive, oxidative and biodesulfurization have also been studied in recent years. Oxidative desulfurization appears to be one of the most promising desulfurization technologies due to its broadness and compatibility with other technologies such as extractive, adsorptive and biodesulfurization. The advent of ionic liquids as extraction solvents has made this even more so. This work, therefore, reviews the different approaches and investigations carried out on oxidative desulfurization while identifying research gaps and giving important recommendations.

N2O emissions from global transportation

Direct emissions of N2O from global transportation (land, air, water) are estimated to be 0.142 ± 0.065 Tg N2O–N yr−1 in 2010 with the majority (≈55%) of emissions resulting as an unwanted by-product from catalytic emission control systems of light-duty vehicles. Emissions from global transportation accounted for 3 ± 1% of current estimates of the total anthropogenic emissions. With anticipated improvements in the emission control systems of light-duty vehicles, the emissions of N2O from global transportation are expected to decline to 0.108 ± 0.065 Tg N2O–N yr−1 by 2030 despite a substantial increase in global transportation activity.

European type-approval test procedure for evaporative emissions from passenger cars against real-world mobility data from two Italian provinces

This paper presents an evaluation of the European type-approval test procedure for evaporative emissions from passenger cars based on real-world mobility data. The study relies on two large databases of driving patterns from conventional fuel vehicles collected by means of on-board GPS systems in the Italian provinces of Modena and Firenze. Approximately 28,000 vehicles were monitored, corresponding to approximately 36millionkilometres over a period of one month. The driving pattern of each vehicle was processed to derive the relation between trip length and parking duration, and the rate of occurrence of parking events against multiple evaporative cycles, defined on the basis of the type-approval test procedure as 12-hour diurnal time windows. These results are used as input for an emission simulation model, which calculates the total evaporative emissions given the characteristics of the evaporative emission control system of the vehicle and the ambient temperature conditions. The results suggest that the evaporative emission control system, fitted to the vehicles from Euro 3 step and optimised for the current type-approval test procedure, could not efficiently work under real-world conditions, resulting in evaporative emissions well above the type-approval limit, especially for small size vehicles and warm climate conditions. This calls for a revision of the type-approval test procedure in order to address real-world evaporative emissions.

Gasoline Cold Start Concept (gCSC™) Technology for Low Temperature Emission Control

Stricter emission standards in the near future require not only a high conversion efficiency of the toxic air pollutants but also a substantial reduction of the greenhouse gases from automotive exhaust. Advanced engines with improved fuel efficiency can reduce the greenhouse gas emissions; their exhaust temperature is, however , also low. This consequently poses significant challenges to the emission control system demanding the catalysts to function at low temperatures both during the cold start period and under the normal engine operation conditions. In this paper, we will introduce a gasoline Cold Start Concept (gCSC™) technology developed for advanced stoichiometric-burn gasoline engines to meet future stringent emission regulations.

Impedance As a Diagnostic Tool to Characterize Mixed-Potential Sensor Response

Commercial tape casting and screen-printing methods have been used to fabricate a planar, self-heated, mixed-potential NOx sensor for application in vehicle on-board emission control systems. The device consists of dense La0.8Sr0.2CrO3 (LSCrO) and Pt electrodes and a porous YSZ electrolyte on one side of a dense ceramic substrate and a Pt-heater with independent leads on the backside of the substrate. While these sensors have demonstrated high sensitivity and selectivity to NOx when operated at a positive bias, optimization of the sensor device geometry remains an open question. In this work, we used circular cells of dense YSZ with LSCrO working and Pt counter electrodes in order to identify the impedance response of each individual sensor component. The impedance response measured on the cell was then used to identify the rate-limiting processes underlying the response of the planar sensor device.

Reduced emissions of CO2, NOx, and SO2 from U.S. power plants owing to switch from coal to natural gas with combined cycle technology

AbstractSince 1997, an increasing fraction of electric power has been generated from natural gas in the United States. Here we use data from continuous emission monitoring systems (CEMS), which measure emissions at the stack of most U.S. electric power generation units, to investigate how this switch affected the emissions of CO2, NOx, and SO2. Per unit of energy produced, natural gas power plants equipped with combined cycle technology emit on an average 44% of the CO2 compared with coal power plants. As a result of the increased use of natural gas, CO2 emissions from U.S. fossil‐fuel power plants were 23% lower in 2012 than they would have been if coal had continued to provide the same fraction of electric power as in 1997. In addition, natural gas power plants with combined cycle technology emit less NOx and far less SO2 per unit of energy produced than coal power plants. Therefore, the increased use of natural gas has led to emission reductions of NOx (40%) and SO2 (44%), in addition to those obtained from the implementation of emission control systems on coal power plants. These benefits to air quality and climate should be weighed against the increase in emissions of methane, volatile organic compounds, and other trace gases that are associated with the production, processing, storage, and transport of natural gas.

Combustion Air Pre-heating from Ash Sensible Heat in Municipal Waste Incineration Systems

Heat recovery from bottom ash is more important in municipal waste combustion systems than in any other solid fuel combustion since almost 50% of it comprises of non-combustibles. In this study, an ash cooling system using air as the cooling medium has been modeled for pre-heating the combustion air. Air cooling has several advantages over water cooling methods. The study involves modeling using Gambit tool and is solved with the fluent solver. Municipal solid waste incineration systems have the advantage of being located near the waste collection area apart from the high volume reduction ratio. Improvements in the emission control systems and combustion technology can make incineration a highly feasible disposal method. Low furnace temperature due to heat losses through fuel moisture loss and ash sensible heat loss has been a disadvantage with these systems. In this study, a small percentage of the combustion air is pre-heated in a non-contact type heat exchanger and its effect on the available energy of combustion gases at the evaporator outlet is studied. The study is performed for two different waste samples. Results indicate significant increase in available energy at the evaporator outlet and better relative performance for the lower grade fuel. A comparison is made with similar methods reported in the literature along with a brief discussion on the methodologies adopted. The results confirm the importance of installing ash sensible heat recovery mechanism for waste incineration systems as well as the feasibility of the air based method.

Results from Testing of Aker Solutions Advanced Amine Solvents at CO2 Technology Centre Mongstad

Abstract The overall objective of the test program at CO2 Technology Centre Mongstad (TCM DA) is to verify Aker Solutions’ Advanced Carbon CaptureTM process including two proprietary advanced amine solvents, ACCTM-solvents S21 and S26. Also a short benchmark campaign is conducted with 30% MEA solvent in order to establish a reference. Key performance results are presented for MEA, S21 and S26. Close to 10 000 hours of operation of the TCM DA amine plant was obtained in the three campaigns, with high availability, showing that there are no operational issues related to the S21 and S26 solvents. Optimum SRD for 30 wt% MEA was found to be 3.8 MJ/kg CO2 when capturing CO2 from CHP gas with CO2 concentration 3.4-4.0% and CO2 capture rate of 87%. SRD was found to be approximately 10% lower for ACCTM advanced solvents S21 and S26. SRD values down to 3.4 MJ/kg CO2 was obtained for CHP flue gas with CO2 concentrations below 4 vol% and 87% capture without heat integration or use of ACCTM Energy Saver. Emissions to atmosphere using ACCTM emission control system were shown to be very low for solvent amines and alkyl amines, with measured levels below 0.1 mg/Nm3 in total. Emission of nitrosamines and nitramines were all below analytical detection limits typically around 0.1 μg/Nm3. Solvent amine losses have been quantified to approximately 2.6 kg amine/ton CO2 captured for MEA, 0.5-0.6 kg amine/ton CO2 captured for ACCTM advanced solvent S21, and 0.2-0.3 kg amine/ton CO2 captured for ACCTM advanced solvent S26. Successful reclaiming of ACCTM advanced solvents S21 and S26 was performed towards the end of the campaigns. Reclaiming was performed for validation purposes and not due to any indications of critical loss of solvent performance, high emissions, high viscosity or other operational problems that could be an indication of excessive degradation. No operational problems such as precipitation or fouling were encountered during reclaiming. HSS and most impurities and degradation products were removed from the solvent by more than 80%.

Controlling Amine Mist Formation in CO2 Capture from Residual Catalytic Cracker (RCC) Flue Gas

Abstract Aker Solutions has developed a novel emission control system involving the combination of anti-mist design and an acid wash polishing step. This concept was tested at a 200 kg/h CO 2 Mobile Test Unit (MTU) operating on flue gas from a Residual Catalytic Cracker (RCC). It was found that the RCC gas contained relatively high concentration of H 2 SO 4 mist (up to 33 mg/Nm 3 ) compared to what is typically seen from a modern coal-fired power station. The high concentration of H 2 SO 4 nuclei generated high amine emission (>200 ppm) when the MTU was operated in conventional mode. On the other hand when the MTU was operated in anti-mist mode the emissions were greatly reduced and amine emissions down to 2 ppm were confirmed by manual emission measurements. A test with conventional mist abatement technology (Brownian diffusion filter) installed upstream the MTU was also performed. It was shown that the filter had large removal efficiency of H 2 SO 4 , however still significant amine emissions persisted when the MTU was not operated in anti-mist mode. The results clearly demonstrate that the Aker Solutions’ Anti-Mist design is an attractive option for mist abatement compared to conventional technology.

Plasma Burner for Active Regeneration of Diesel Particulate Filter

This study proposes a diesel particulate filter system to remove particulate matter (PM) from diesel engines. Filters should be periodically burned (regenerated) to remove PM. In the proposed system, a plasma burner is utilized for filter regeneration. The plasma burner avoids the drawbacks of the electric heater and full-flow-type diesel burner by successively discharging and partially oxidizing the fuel, which produces hydrogen for flame stabilization under all revolution per minute and load conditions. The proposed system was verified by field testing three different vehicles for over 20,000 km. The field test results confirmed successful PM removal and the simultaneous removal of other emissions such as CO, NOx, and hydrocarbons. The plasma burner is applicable to the thermal management of emission control systems for both retrofitted and original equipment manufacturer cars.

Development of a Real-Time NOx Prediction Model Based on Heat Release Analysis in a Direct-Injection Diesel Engine

A prediction model, which describes linear relationship between the nitrogen oxides (NOx) emissions and the in-cylinder heat release rate in a direct-injection diesel engine, was developed through numerical simulations. A modified KIVA-3 V code was used to calculate NOx formations and to conduct heat release analyses in a direct-injection diesel engine under different operating conditions. The numerical simulation results indicated that the NOx formation amount was related to both the magnitude and the timing of the peak heat release rate in each engine cycle. Based on the above observations, a control-oriented dynamic NOx model was constructed and then implemented into a feedback emission control system on a small diesel engine. A new parameter—combustion acceleration—was proposed in this research to describe the intensity of the premixed combustion. Experimental work was also conducted to measure the real-time in-cylinder pressure at each crank-angle when the engine was running and the heat release rate was calculated instantaneously to control an exhaust gas recirculation (EGR) valve. The experimental results showed that the proposed NOx prediction model was effective in controlling NOx emissions under high rpm conditions.

Use of Confidence Limits to Set Robust On-Board Diagnostic Thresholds

Vehicles sold in the United States and Europe are equipped with a specific set of legal diagnostics, called on-board diagnostics; these are used to monitor the performance of various elements of the emission control system. The driver is informed of any failures by the use of a Check Engine Light on the dashboard of the vehicle and then should return the vehicle to the dealership for rectification. The vehicle manufacturer’s aim is to ensure that the Check Engine Light is only illuminated for legitimate failures. For the calibration of an on-board diagnostics, there needs to be sufficient separation between the response of a good sensor and a failed sensor; the setting of this threshold should be based upon a statistical model of the data so that the predicted failures rate can then be determined. An additional benefit of obtaining a statistical model is that it allows confidence limits to be applied to the data; this then gives the engineer the ability to determine the trade-off between the number of data points and the confidence in the estimated statistical model.

Review of fly ash as a soil amendment

Worldwide, about 500 million tonnes of coal combustion by-products (CCPs) are produced annually. Fly ash constitutes 70% of the by-products generated, and these ashes vary in their composition and properties based on the boiler type and the gas emission control system. Fly ashes are used as fill material, alkaline amendments, cement, and grout material. Because of high-soluble salt content and leachable macro and micronutrients, they can be used as a soil amendment to replace fertilizer and lime. Alkaline fly ashes can be added in large quantities to neutralize acidity and raise pH associated with acid soils. Care should be taken to ensure that sufficient quantities of alkalinity are added so that fly ash does not become acid stripped, thereby releasing high levels of elements that can become toxic. Fly ashes can also improve soils with poor physical properties. Coarse-textured or rocky soils can be amended with fly ash to increase the silt- and sand-sized fractions, which help in aggregation, infiltration, and water-holding capacity. Research has demonstrated positive benefits of fly ash addition for improving soil properties and in increasing crop yields. Results also documented no detrimental effects with application of fly ashes to acid, neutral, or saline-sodic soils.

Oxidation Potentials in Iron and Steel Making

The state of oxidation of a pyrometallurgical process given by the partial pressure of oxygen and the temperature (the oxidation potential) is one of the important properties monitored and controlled in the smelting and refining of iron and the nonferrous metals. Solid electrolyte sensors based on ZrO2 and a reference electrode such as Cr/Cr2O3 to measure the oxygen pressure found early application in the steel industry, followed soon after in copper, nickel, lead, and zinc smelting. Similar devices are installed in automobile postcombustion/exhaust trains as part of emission control systems. The current discussion reviews this technology as applied in the primary steps of iron and steel making and refining.