To further increase efficiency, it is necessary to optimise the combustion and exhaust gas aftertreatment systems so that additional fuel consumption as a result of aftertreatment is minimised. As the engine is operated with a rich mixture during regeneration phases, fuel consumption is increased. During regeneration, stored NO x is released and reduced to N 2. As the NO x storage capacity of these catalysts is limited, the engine must be briefly operated with rich mixtures ( λ < 1) during regeneration phases. During lean-burn operation, combustible hydrocarbons and carbon monoxide are readily oxidised due to the high proportion of oxygen.On the other hand, NO x adsorber catalysts (De-NO x catalysts also called NO x storage catalysts) must be used to reduce the nitrogen oxide produced during lean-burn operation ( λ > 1). There i.Gasoline direct injection is characterised by a variety of air-fuel ratios, ranging from extremely lean mixtures (part load) in stratified charge operation to rich mixtures (full load).
The exhaust gas after the reaction of the AOP reactor is withdrawn from the tail gas draft fan into the ozone exhaust gas absorption device, and the temperature is raised in the exhaust gas destruction system through the preheating device (the initial operation is used and normally deactivated), and then the catalytic reaction is carried out directly, so that the reaction of ozone and carbon can produce carbon dioxide and oxygen. When the concentration is >0.1 ppm, it can cause some irritation to the human body, so the reaction after the exhaust must be treated to discharge it into the atmospheric environment. As sulphur in the fuel contaminates the storage converter, engines with this exhaust gas treatment system cannot be used in countries where fuel of the necessary quality does not exist.Zhao Youcai, Wei Ran, in Biomethane Production from Vegetable and Water Hyacinth Waste, 2021 6.13.5.4 Absorption and decomposition device of ozone exhaust gasThe exhaust gas from the AOP reactor will contain a certain amount of incompletely reacted ozone.
The air reference side becomes electrically more negative than the exhaust gas side therefore, an electric field exists across the ZrO 2 material and a voltage, V o, results. The ZrO 2 has a tendency to attract the oxygen ions, which accumulate on the ZrO 2 surface just inside the platinum electrodes.The platinum plate on the air reference side of the ZrO 2 is exposed to a much higher concentration of oxygen ions than the exhaust gas side. Oxygen ions have two excess electrons such that the ions are negatively charged. The inside electrode is exposed to air, and the outside electrode is exposed to exhaust gas through a porous protective overcoat.A simplified explanation of EGO sensor operation is based on the distribution of oxygen ions. (A) Picture of exemplary EGO sensor (B) Illustrative installation and (C) Exposure to exhaust gas.In essence, the EGO sensor consists of a thimble-shaped section of ZrO 2 with thin platinum electrodes on the inside and outside of the ZrO 2. Illustration of EGO sensor.
The oxygen partial pressure for a lean mixture is roughly 10 − 2 atm. The exhaust gas oxygen partial pressure for a rich mixture varies over the range of 10 − 16–10 − 32 of atmospheric pressure. Basically, this partial pressure is that proportion of the total exhaust gas pressure slightly above (but nearly at atmospheric pressure) that is due to the concentration of oxygen in the composite exhaust gas. The magnitude of this voltage depends on the concentration of oxygen in the exhaust gas and on the sensor temperature.The quantity of oxygen in the exhaust gas is represented by the oxygen partial pressure.
The EGO sensor should not be used for control at temperatures below about 300☌ because the difference between rich and lean voltages decreases rapidly with temperature in this region. EGO sensor temperature characteristics.Under certain conditions, the fuel control using an EGO sensor will be operated in open-loop mode, and for other conditions, it will be operated in closed-loop mode (as will be explained in Chapter 6). Desirable EGO characteristicsFig. For a fully warmed EGO sensor, the output voltage is about 1 V for a rich mixture and about 0.1 V for a lean mixture.
However, if the gas turbine power is below 5-7 MW and motor power below 8-12 MW, a water vapour process is difficult to achieve with good efficiency, and an ORC process may be more favourable. In such large gas turbine plants and also in very big motor power plants, high efficiency is obtained by using a steam process with several pressure levels. Although it is important to hasten the change from open- to closed-loop operation (particularly during a cold engine start), the EGO sensor voltage must be sufficient for closed-loop operation.Exhaust gases from gas turbines and internal combustion engines can be recovered effectively by means of an ORC power plant, thus considerably increasing the overall energy conversion of the combined system, much like in modern large combined-cycle power plants. Open-loop mode operation is undesirable since exhaust emission regulation is not as reliable as closed-loop operation particularly as a vehicle ages and engine parameters can change. Closed-loop operation with the EGO output voltage used as the error input cannot begin until the EGO sensor temperature exceeds about 300☌.
Conversion rates increase with temperature and thus it is advantageous to place this catalyst near the HRSG inlet. Oxidation catalysts like the SCR unit are housed within an HRSG at an appropriate temperature and are typically formulated with platinum group metals to achieve maximum conversion of the pollutants. However, oxidation catalysts are available that can provide greater than 90% destruction of CO, VOCs, formaldehyde and other toxic compounds. Rao, in Combined Cycle Systems for Near-Zero Emission Power Generation, 2012 Post-combustion CO 2 capture casesExhaust gas recycle has the potential for increasing the formation of CO and VOCs. Many of these smaller motors are run with biogas, which makes this application particularly favourable for the environment.A.D. The minimum gas turbine power for present day economically feasible ORC is probably about 0.5 MW and minimum motor power probably about 1 MW (future development may decrease these limits).
One is the environmentally benign catalysts, including the original design strategy and reaction mechanisms. After introducing SCR reaction and important related details, two critical topics are discussed. The main reaction of SCR is NOx reduced by NH 3 to N 2, and H 2O. Selective catalytic reduction (SCR) with ammonia is the most effective method for NOx removal. NOx emission leads to the acid rain formation, photochemical smog pollution and secondary aerosols. Among these, NOx is a major air pollutant in most of the developing countries, such as China and India, etc.
During the studies outlined in this chapter in situ spectroscopy technology was analyzed and the nanomaterials electronic structure calculations were conducted.
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