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Analytical Measurements
Published in Douglas O. J. deSá, Instrumentation Fundamentals for Process Control, 2019
When a calibration gas containing a known amount of oxygen is made to flow through the measuring chamber, the dumbbell will try to rotate by an amount brought about by the paramagnetic constituents moving to congregate at the strongest part of the magnetic field, thus upsetting the balance. As soon as the dumbbell moves, the optical detecting system “sees” the movement and drives the amplifier to change the current flow to the feedback coil to maintain the dumbbell at its zero position. This current, proportional to the volume magnetic susceptibility of the gas mixture in the measuring chamber, is displayed on an indicator having a scale calibrated in terms of percent oxygen. The measured gas causes the same behavior of the sensor. Because the measurement produced is proportional to the partial pressure of the oxygen present in the gas sample, it is directly proportional to the absolute value at atmospheric pressure. Provided that they are not excessive, the instrument is fairly insensitive to other gases in the sample, to sample flow, and to tilt. These analyzers have applications in inerting, fermentation, blast furnaces, chemical production, biotechnology and physiology. (Inerting is a procedure used to describe the replacement of air in a process vessel by an inert gas; the replacement gas is usually nitrogen. The “atmosphere” within the vessel is continuously monitored for the presence of oxygen and more nitrogen added if required to eliminate the oxygen.)
Preentry Planning, Hazard Assessment, and Hazard Management
Published in Neil McManus, Safety and Health in Confined Spaces, 2018
Inerting is a technique using a nonreactive gas, such as nitrogen, to reduce the concentration of oxygen to levels below which combustion cannot occur (API 1987). Inerting could be essential where residual contents continue to evolve flammable vapor or where flammable gas or vapor can seep into the space. Inerting also is required in spaces containing substances that react with oxygen in air. Substances requiring inerting include pyrophores, such as iron sulfide, and unregenerated catalysts, strong oxidizers, such as peroxides, that promote oxidation; and reactive substances that undergo a self-accelerating exothermic reaction when a critical temperature is reached.
Fire Resistance and Fire-Resistant Hydraulic Fluids
Published in Leslie R. Rudnick, Synthetics, Mineral Oils, and Bio-Based Lubricants, 2020
Gas inerting systems are limited to operation in a relatively small volume and are not practical for large industrial plants. However, even these have their limitations in terms of requiring leakproof enclosures and significant storage space for the gases, while both types of protection will not function efficiently without regular maintenance.
Design Novel Environmentally-friendly Flame Retardants
Published in Combustion Science and Technology, 2023
Rui Zhai, Zhao Yang, Yubo Chen, Yong Zhang, Zijian Lv
According to the inerting mechanism, flame retardants can be divided into physical flame retardants (Carbon dioxide (CO2), Nitrogen (N2), inert gas, etc.) and chemical flame retardants (1,1,1,2-Tetrafluoroethane (R134a), 1,1,1,3,3-Pentafluoropropane (R245fa), Pentafluoroethane (R125), 1,1,1,2,3,3,3-Heptafluoropropane (R227ea), etc.) in energy conversion cycle. Physical flame retardants prevent the combustion process by cooling the temperature of the reaction system, diluting the concentration of the reaction gases, covering the combustible gas or blocking the contact of the combustible gas with oxygen. Chemical flame retardants stave burning through making chemical reactions with flammable gases, reactive free radicals, and spark centers, as a result of competition with combustion. Obviously, chemical flame retardants are superior in terms of the perfect effect of inflaming retarding.
Countermeasures against coal spontaneous combustion: a review
Published in International Journal of Coal Preparation and Utilization, 2022
During the incident of an endogenous fire in goafs or other sections of the mine, the ventilation air stream becomes a cause of oxygen that facilitates the process of coal oxidation and a carrier of fumes and fire gases travels to the next mine workings. Hence, it is important, in terms of safety, to sustain the optimum composition of the atmosphere. This is obtainable by goafs’ inertisation process. Inerting is the mechanism by which substances (such as an inert gas) are introduced into the goafs to decrease the concentration of oxygen; it contributes to or does not cause the SPONCOM of coal to begin at all. One of the most direct and reliable measures of the degree of SPONCOM is coal temperature (Sensogut, Ozdeniz, and Gundogwu 2008; Taraba, Peter, and Slovak 2011; Yu et al. 2017). Although the mined-out area in a coal mine is a closed space that is difficult to reach to test temperatures. In addition, coal is a weak heat conductor and air mobility within a mine is limited. It is also difficult, by explicitly calculating coal temperatures in the goaf, to precisely evaluate SPONCOM locations.
All-Silicon Zeolite Supported Pt Nanoparticles for Green On-Board Inert Gas Generation System
Published in Combustion Science and Technology, 2021
Wenqi Zhao, Yitong Dai, Xinxin Cheng, Sanshu Xu, Yongsheng Guo, Wenjun Fang
There are several methods for fuel tank inerting, such as explosion suppressant foam, the liquid nitrogen system, the Halon extinguishment system and the on-board inert gas generation system (OBIGGS). However, there are still some disadvantages even for the most commonly used OBIGGS (Shao et al. 2018b; Renouard-Vallet et al. 2012), such as extra fuel consumption during engine bleed air process, an additional increase in aircraft weight, and negative impacts on engine performance. To overcome these flaws, the Green On-board Inert Gas Generation System (GOBIGGS) was developed gradually as a new type of oxygen-consuming fuel tank inerting system (Limaye and Koenig 2008; Limaye et al. 2011; Morris, Miller, Limaye 2006). The working principle for GOBIGGS is shown in Figure 1. In the GOBIGGS system, the fuel/air mixtures in the fuel tank ullage are delivered to the flameless combustion unit, where the blending gas will produce a flameless combustion reaction with the presence of the catalyst. The oxygen can be consumed in the process, while the generated water can be removed after condensation, and the produced carbon dioxide will participate in fuel tank inerting. After reciprocal cycles, the oxygen content can be controlled below the safety line quickly. Obviously, in the inerting system with GOBIGGS, the catalytic combustion reactor is one of the core components, and the performance of the catalyst is key to ensuring the efficient operation of this component.