No abstract

No abstract

No abstract

Low-NOx technologies are widely used in pulverized coal boilers, but they usually produce high levels of carbon in the fly ash. High levels of unburned carbon represent fuel loss, so the overall boiler efficiency is reduced. Additionally, the higher carbon content affects the suitability of fly ash for cement applications. The purpose of this paper is to provide a CFD approach for unburned carbon reduction by optimizing operating conditions. In this paper, three different boiler loads were simulated: 200 MW, 170 MW, and 140 MW. The air supply system was simulated previously for preparing as precise as possible boundary conditions. At last, unburned carbon level of every burner was investigated, and the effects of residue residence time and the local fuel-air momentum ratio are discussed in detail. According to the predicted results, operating conditions and the residence time of the coal particles affects the unburned carbon level in fly ash. Operating conditions plays a more significant role during the combustion process, while the residence time affects char burnout only when the burner's location is low. Therefore, it is concluded that a cost effective method could be developed for reducing the unburned carbon level in ash and correspondingly, the loss on ignition level. First, it is necessary to determine which burners are operating under poor conditions through CFD analysis. Then, the fuel air momentum ratios of those burners should be modified by changing the operating conditions, meanwhile, increasing residence time of coal particles to ensure complete combustion.

Alpha-1-antitrypsin is a potent antiprotease playing an important role in maintaining protease-antiprotease balance. It protects the structures of extracellular matrix against destruction by proteolytic enzymes. Loss of elasticity occurs when increased protease activity is accompanied by qualitative impairment or reduced concentrations of antiproteases. Alpha-1-antitrypsin deficiency is a risk factor for obstructive lung disease, including emphysema, liver and kidney disorders and, less often, follicular panniculitis, granulomatosis with polyangiitis (previously Wegener's granulomatosis). Literature also emphasises the role of AAT in the development of aortic aneurysms, and results of biochemical studies support this theory. Aortic aneurysm is an important clinical problem, unceasingly associated with high mortality. For this reason, it is exceptionally important to identify its risk factors. Studies on the relationship between AAT and development of AAA (abdominal aortic aneurysm) have been conducted since the 1990s. Due to the development in molecular diagnostic techniques, new reports on the topic appeared over the last decade.